Duration of efficacy of treatment of latent tuberculosis infection in HIV-infected adults

Predicted choice and acceptability of regimens for tuberculosis preventive treatment among people living with HIV in Uganda - a discrete choice experiment

Introduction

Little is known about how people living with HIV would choose if offered different tuberculosis preventive treatment (TPT) regimens, and under which conditions they would accept treatment. Actionable evidence regarding preference for TPT is needed to inform policy and the development of novel TPT regimens.

Methods

Adults engaged in care at an HIV clinic in Kampala, Uganda, completed a discrete choice experiment survey with nine random choice tasks. In each task, participants first chose between two hypothetical TPT regimens with differing treatment features (number of pills, frequency, duration, adjusted antiretroviral dosage, and side effects). Second, they answered if they would accept the selected treatment, versus taking no treatment. We simulated predicted TPT regimen choice based on hierarchical Bayesian estimation of individual preference weights.

Results

Among 400 participants, 394 gave high-quality answers and were included (median age 44, 71.8% female, 91.4% previously received TPT). Across nine tasks, 60.2% (237/394) accepted all selected TPT regimens, 39.3% (155/394) accepted some regimens, and 0.5% (2/394) accepted none. Regimens requiring antiretroviral dosage adjustment were more likely to be unacceptable (adjusted odds ratio, aOR 27.4, 95% confidence interval [CI] 18.5 - 40.7), as were regimens requiring more pills per dose (aOR 24.5 [95% CI 16.6 - 36.3] for 10 pills compared to 1 or 5 pills per dose). Choice simulations showed that if only 6 months of daily isoniazid (6H) was available, 11.9% would prefer no TPT. However, offering a 4-pill, fixed-dose combination 3HP regimen in addition to 6H increased the acceptability from 88.1% to 98.8% (predicted choice of 3HP 94.5%, 6H 4.4%, no TPT 1.2%).

Conclusions

While adults living with HIV in Uganda demonstrate a high willingness to accept different TPT regimens, offering regimens with preferred features, such as 3HP as a fixed-dose combination, could drive TPT acceptance and uptake from high to nearly universal.

A Meta-Analysis of Levofloxacin for Contacts of Multidrug-Resistant Tuberculosis

BACKGROUND

Data from randomized trials evaluating the effectiveness of tuberculosis (TB) preventive treatment for contacts of multidrug-resistant (MDR)-TB are lacking. Two recently published randomized trials that did not achieve statistical significance provide the opportunity for a meta-analysis.

METHODS

We conducted combined analyses of two phase 3 trials of levofloxacin MDR-TB preventive treatment - Levofloxacin for the Prevention of Multidrug-Resistant Tuberculosis (VQUIN) trial and the Levofloxacin preventive treatment in children exposed to MDR-TB (TB-CHAMP) trial. Following MDR-TB household exposure, VQUIN enrolled mainly adults in Vietnam; TB-CHAMP enrolled mainly young children in South Africa. Random assignment in both trials was 1:1 at the household level to daily levofloxacin or placebo for 6 months. The primary outcome was incident TB by 54 weeks. We estimated the treatment effect overall using individual participant data meta-analysis.

RESULTS

The VQUIN trial (n=2041) randomly assigned 1023 participants to levofloxacin and 1018 participants to placebo; TB-CHAMP (n=922) assigned 453 participants to levofloxacin and 469 participants to placebo. Median age was 40 years (interquartile range 28 to 52 years) in VQUIN and 2.8 years (interquartile range 1.3 to 4.2 years) in TB-CHAMP. Overall, 8 levofloxacin-group participants developed TB by 54 weeks versus 21 placebo-group participants; the relative difference in cumulative incidence was 0.41 (95% confidence interval [CI] 0.18 to 0.92; P=0.03). No association was observed between levofloxacin and grade 3 or above adverse events (risk ratio 1.07, 95% CI 0.70 to 1.65). Musculoskeletal events of any grade occurred more frequently in the levofloxacin group (risk ratio 6.36, 95% CI 4.30 to 9.42), but not among children under 10 years of age. Overall, four levofloxacin-group participants and three placebo-group participants had grade 3 events.

CONCLUSIONS

In this meta-analysis of two randomized trials, levofloxacin was associated with a 60% relative reduction in TB incidence among adult and child household MDR-TB contacts, but with an increased risk of musculoskeletal adverse events. (Funded by the Australian National Health and Medical Research Council, UNITAID, and others.).

Efficacy of anti-tuberculosis drugs for the treatment of latent tuberculosis infection: a systematic review and network meta-analysis

Despite the availability of three network meta-analyses (NMA) examining the efficacy, treatment completion, and adverse events associated with all latent tuberculosis infection (LTBI) treatments, there is currently no evidence to support the notion that the benefits of these treatments outweigh the potential risks. This NMA aimed to conduct a comprehensive comparison and update of the efficacy, treatment completion rates and adverse events associated with recommended treatment options for LTBI for individuals with confirmed LTBI, as outlined in the 2020 World Health Organization (WHO) Consolidated Guidelines for TB preventive treatment. A comprehensive search of the MEDLINE and Scopus databases was conducted until April 2023. The NMA was applied to estimate the risk difference and corresponding 95% confidence interval (CI) using a combination of direct and indirect evidence. The risk-benefit assessment was employed to evaluate the feasibility of the extra benefits in relation to the extra risks. The primary outcomes of interest in this study were active TB disease, completion rates, and adverse events. The meta-analysis incorporated data from 15 studies, which collectively demonstrated that the administration of a placebo resulted in a significant increase in the risk of developing TB disease by 1.279%, compared to the daily intake of isoniazid for 6 months (6H). Furthermore, treatment completion rates were significantly higher when using isoniazid plus rifapentine weekly for 3 months (3HP) and rifampicin daily for 4 months (4R), as compared to 6H. Considering adverse events, the combination of 3HP, 4R, and isoniazid administered daily for 9 months (referred to as 9H) significantly decreased adverse events by 4.53% in comparison to 6H. The risk-benefit assessment showed that alternative treatment regimens (9H, 4R, 3HR and 3HP) had a lower incidence of adverse events, while demonstrating a higher efficacy in preventing TB, as compared to 6H. This review indicates that there were no significant differences observed among various active treatment options in terms of their efficacy in preventing active TB. Moreover, completion rates were higher in 3HP and 4R, and a reduction in adverse events was observed in 3HP, 4R, and 9H.

Completion, safety, and efficacy of tuberculosis preventive treatment regimens containing rifampicin or rifapentine: an individual patient data network meta-analysis

BACKGROUND

3 months of weekly rifapentine plus isoniazid (3HP) and 4 months of daily rifampicin (4R) are recommended for tuberculosis preventive treatment. As these regimens have not been compared directly, we used individual patient data and network meta-analysis methods to compare completion, safety, and efficacy between 3HP and 4R.

METHODS

We conducted a network meta-analysis of individual patient data by searching PubMed for randomised controlled trials (RCTs) published between Jan 1, 2000, and Mar 1, 2019. Eligible studies compared 3HP or 4R to 6 months or 9 months of isoniazid and reported treatment completion, adverse events, or incidence of tuberculosis disease. Deidentified individual patient data from eligible studies were provided by study investigators and outcomes were harmonised. Methods for network meta-analysis were used to generate indirect adjusted risk ratios (aRRs) and risk differences (aRDs) with their 95% CIs.

FINDINGS

We included 17 572 participants from 14 countries in six trials. In the network meta-analysis, treatment completion was higher for people on 3HP than for those on 4R (aRR 1·06 [95% CI 1·02-1·10]; aRD 0·05 [95% CI 0·02-0·07]). For treatment-related adverse events leading to drug discontinuation, risks were higher for 3HP than for 4R for adverse events of any severity (aRR 2·86 [2·12-4·21]; aRD 0·03 [0·02-0·05]) and for grade 3-4 adverse events (aRR 3·46 [2·09-6·17]; aRD 0·02 [0·01-0·03]). Similar increased risks with 3HP were observed with other definitions of adverse events and were consistent across age groups. No difference in the incidence of tuberculosis disease between 3HP and 4R was found.

INTERPRETATION

In the absence of RCTs, our individual patient data network meta-analysis indicates that 3HP provided an increase in treatment completion over 4R, but was associated with a higher risk of adverse events. Although findings should be confirmed, the trade-off between completion and safety must be considered when selecting a regimen for tuberculosis preventive treatment.

FUNDING

None.

TRANSLATIONS

For the French and Spanish translations of the abstract see Supplementary Materials section.

Efficacy, safety, and tolerability of isoniazid preventive therapy for tuberculosis in people living with HIV

OBJECTIVE

The aim of this study was to systematically assess the efficacy, safety, and tolerability of isoniazid preventive therapy (IPT) for tuberculosis (TB) in people with HIV (PWH).

DESIGN

A systematic review and meta-analysis.

METHODS

A thorough literature search was performed using PubMed, Cochrane CENTRAL, and Google Scholar from their inception to June 30, 2021. All randomized controlled trials (RCTs) investigating the efficacy, safety, or tolerability of IPT on PWH compared with placebo or active comparators were included in the study. The heterogeneity among the studies was identified by using the I2 statistic and Cochran's Q test.

RESULTS

Out of the 924 nonduplicate RCTs identified through database searching and other sources, 26 studies comprising 38 005 patients were included. The overall effect estimate identified the reduction of active TB incidence [odds ratio (OR) 0.69; 95% confidence interval (95% CI) 0.57-0.84; P  < 0.001], but not all-cause mortality (OR 0.91; 95% CI 0.82, 1.02; P  = 0.10) with IPT compared with the control. In addition, no significant association was identified between the use of IPT and the risk of peripheral neuropathy (OR 1.50; 95% CI 0.96-2.36; P  = 0.08) and hepatotoxicity (OR 1.21; 95% CI 0.97-1.52; P  = 0.09).

CONCLUSION

This systematic review and meta-analysis identified a significant reduction in the incidence of active TB, but not all-cause mortality, among PWH who received IPT compared with the control. Lesser number of outcomes may be the reason for nonsignificant results in terms of safety outcomes of IPT. Therefore, there is a need for extensive and long-term studies to address these issues further, especially in TB/HIV endemic areas.

Tuberkulose im Erwachsenenalter

Die Tuberkulose ist in Deutschland eine seltene, überwiegend gut behandelbare Erkrankung. Weltweit ist sie eine der häufigsten Infektionserkrankungen mit ca. 10 Millionen Neuerkrankungen/Jahr. Auch bei einer niedrigen Inzidenz in Deutschland bleibt Tuberkulose insbesondere aufgrund der internationalen Entwicklungen und Migrationsbewegungen eine wichtige Differenzialdiagnose. In Deutschland besteht, aufgrund der niedrigen Prävalenz der Erkrankung und der damit verbundenen abnehmenden klinischen Erfahrung, ein Informationsbedarf zu allen Aspekten der Tuberkulose und ihrer Kontrolle. Diese Leitlinie umfasst die mikrobiologische Diagnostik, die Grundprinzipien der Standardtherapie, die Behandlung verschiedener Organmanifestationen, den Umgang mit typischen unerwünschten Arzneimittelwirkungen, die Besonderheiten in der Diagnostik und Therapie resistenter Tuberkulose sowie die Behandlung bei TB-HIV-Koinfektion. Sie geht darüber hinaus auf Versorgungsaspekte und gesetzliche Regelungen wie auch auf die Diagnosestellung und präventive Therapie einer latenten tuberkulösen Infektion ein. Es wird ausgeführt, wann es der Behandlung durch spezialisierte Zentren bedarf.

Die Aktualisierung der S2k-Leitlinie „Tuberkulose im Erwachsenenalter“ soll allen in der Tuberkuloseversorgung Tätigen als Richtschnur für die Prävention, die Diagnose und die Therapie der Tuberkulose dienen und helfen, den heutigen Herausforderungen im Umgang mit Tuberkulose in Deutschland gewachsen zu sein.

Effectiveness of a 6-Month Isoniazid on Prevention of Incident Tuberculosis Among People Living with HIV in Eritrea: A Retrospective Cohort Study

Introduction

A 6-month isoniazid as tuberculosis preventive therapy (TPT) for people living with HIV (PLHIV) was nationally introduced in Eritrea in 2014. However, its effectiveness in preventing tuberculosis (TB) and duration of protection was questioned by physicians. This study was, therefore, conducted to evaluate the impact of the isoniazid preventive therapy (IPT) primarily on the prevention of TB and duration of its protection in PLHIV.

Methods

A retrospective cohort study was conducted that selected all eligible PLHIV attending HIV care clinics in all national and regional referral hospitals in Eritrea. Data was collected from patients’ clinical cards using a structured data extraction sheet. The association between use of IPT and outcomes of interest was assessed using a Cox proportional hazard regression model and Kaplan–Meier curve.

Results

A total of 6803 patients were selected, which accounted for 75% of all PLHIV-accessing HIV care clinics in Eritrea. About 76% of patients were exposed to IPT while the remaining 24% were unexposed. The mean follow-up time was 4.9 years (SD 1.4). The incidence rate of TB was 1.7 and 10 cases per 1000 person-years in the exposed and unexposed, respectively. The unexposed had a higher risk of incident TB (adjusted hazard ratio [aHR] 3.75, 95% confidence interval [CI] 2.89, 6.13) and all-cause mortality (HR 2.41, 95% CI 1.85, 3.14) compared to the exposed. A Kaplan–Meier curve showed that the exposed group had a higher TB-free follow-up probability (98.8%) compared to the unexposed (95%) at 65 months of follow-up (p < 0.001). IPT protection decreased rapidly 6 months after isoniazid completion.

Conclusion

Use of a 6-month isoniazid as TPT was found to be effective in reducing incident TB in PLHIV-accessing HIV care clinics in Eritrea. However, the protection appeared to diminish soon, namely 6 months after completion of isoniazid, which warrants immediate attention from policy makers.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40121-022-00589-w.

Plasma host protein biomarkers correlating with increasing Mycobacterium tuberculosis infection activity prior to tuberculosis diagnosis in people living with HIV

BACKGROUND

Biomarkers correlating with Mycobacterium tuberculosis infection activity/burden in asymptomatic individuals are urgently needed to identify and treat those at highest risk for developing active tuberculosis (TB). Our main objective was to identify plasma host protein biomarkers that change over time prior to developing TB in people living with HIV (PLHIV).

METHODS

Using multiplex MRM-MS, we investigated host protein expressions from 2 years before until time of TB diagnosis in longitudinally collected (every 3-6 months) and stored plasma from PLHIV with incident TB, identified within a South African (SA) and US cohort. We performed temporal trend and discriminant analyses for proteins, and, to assure clinical relevance, we further compared protein levels at TB diagnosis to interferon-gamma release assay (IGRA; SA) or tuberculin-skin test (TST; US) positive and negative cohort subjects without TB. SA and US exploratory data were analyzed separately.

FINDINGS

We identified 15 proteins in the SA (n=30) and 10 in the US (n=24) incident TB subjects which both changed from 2 years prior until time of TB diagnosis after controlling for 10% false discovery rate, and were significantly different at time of TB diagnosis compared to non-TB subjects (p<0.01). Five proteins, CD14, A2GL, NID1, SCTM1, and A1AG1, overlapped between both cohorts. Furthermore, after cross-validation, panels of 5 - 12 proteins were able to predict TB up to two years before diagnosis.

INTERPRETATION

Host proteins can be biomarkers for increasing Mycobacterium tuberculosis infection activity/burden, incipient TB, and predict TB development in PLHIV.

FUNDING

NIH/NIAID AI117927, AI146329, and AI127173 to JMA.

Annual Tuberculosis Preventive Therapy for Persons With HIV Infection : A Randomized Trial

BACKGROUND

Tuberculosis preventive therapy for persons with HIV infection is effective, but its durability is uncertain.

OBJECTIVE

To compare treatment completion rates of weekly isoniazid-rifapentine for 3 months versus daily isoniazid for 6 months as well as the effectiveness of the 3-month rifapentine-isoniazid regimen given annually for 2 years versus once.

DESIGN

Randomized trial. (ClinicalTrials.gov: NCT02980016).

SETTING

South Africa, Ethiopia, and Mozambique.

PARTICIPANTS

Persons with HIV infection who were receiving antiretroviral therapy, were aged 2 years or older, and did not have active tuberculosis.

INTERVENTION

Participants were randomly assigned to receive weekly rifapentine-isoniazid for 3 months, given either annually for 2 years or once, or daily isoniazid for 6 months. Participants were screened for tuberculosis symptoms at months 0 to 3 and 12 of each study year and at months 12 and 24 using chest radiography and sputum culture.

MEASUREMENTS

Treatment completion was assessed using pill counts. Tuberculosis incidence was measured over 24 months.

RESULTS

Between November 2016 and November 2017, 4027 participants were enrolled; 4014 were included in the analyses (median age, 41 years; 69.5% women; all using antiretroviral therapy). Treatment completion in the first year for the combined rifapentine-isoniazid groups (n = 3610) was 90.4% versus 50.5% for the isoniazid group (n = 404) (risk ratio, 1.78 [95% CI, 1.61 to 1.95]). Tuberculosis incidence among participants receiving the rifapentine-isoniazid regimen twice (n = 1808) or once (n = 1802) was similar (hazard ratio, 0.96 [CI, 0.61 to 1.50]).

LIMITATION

If rifapentine-isoniazid is effective in curing subclinical tuberculosis, then the intensive tuberculosis screening at month 12 may have reduced its effectiveness.

CONCLUSION

Treatment completion was higher with rifapentine-isoniazid for 3 months compared with isoniazid for 6 months. In settings with high tuberculosis transmission, a second round of preventive therapy did not provide additional benefit to persons receiving antiretroviral therapy.

PRIMARY FUNDING SOURCE

The U.S. Agency for International Development through the CHALLENGE TB grant to the KNCV Tuberculosis Foundation.

Tuberculosis preventive therapy for people living with HIV: A systematic review and network meta-analysis

BACKGROUND

Tuberculosis (TB) preventive therapy (TPT) is an essential component of care for people living with HIV (PLHIV). We compared efficacy, safety, completion, and drug-resistant TB risk for currently recommended TPT regimens through a systematic review and network meta-analysis (NMA) of randomized trials.

METHODS AND FINDINGS

We searched MEDLINE, Embase, and the Cochrane Library from inception through June 9, 2020 for randomized controlled trials (RCTs) comparing 2 or more TPT regimens (or placebo/no treatment) in PLHIV. Two independent reviewers evaluated eligibility, extracted data, and assessed the risk of bias. We grouped TPT strategies as follows: placebo/no treatment, 6 to 12 months of isoniazid, 24 to 72 months of isoniazid, and rifamycin-containing regimens. A frequentist NMA (using graph theory) was carried out for the outcomes of development of TB disease, all-cause mortality, and grade 3 or worse hepatotoxicity. For other outcomes, graphical descriptions or traditional pairwise meta-analyses were carried out as appropriate. The potential role of confounding variables for TB disease and all-cause mortality was assessed through stratified analyses. A total of 6,466 unique studies were screened, and 157 full texts were assessed for eligibility. Of these, 20 studies (reporting 16 randomized trials) were included. The median sample size was 616 (interquartile range [IQR], 317 to 1,892). Eight were conducted in Africa, 3 in Europe, 3 in the Americas, and 2 included sites in multiple continents. According to the NMA, 6 to 12 months of isoniazid were no more efficacious in preventing microbiologically confirmed TB than rifamycin-containing regimens (incidence rate ratio [IRR] 1.0, 95% CI 0.8 to 1.4, p = 0.8); however, 6 to 12 months of isoniazid were associated with a higher incidence of all-cause mortality (IRR 1.6, 95% CI 1.2 to 2.0, p = 0.02) and a higher risk of grade 3 or higher hepatotoxicity (risk difference [RD] 8.9, 95% CI 2.8 to 14.9, p = 0.004). Finally, shorter regimens were associated with higher completion rates relative to longer regimens, and we did not find statistically significant differences in the risk of drug-resistant TB between regimens. Study limitations include potential confounding due to differences in posttreatment follow-up time and TB incidence in the study setting on the estimates of incidence of TB or all-cause mortality, as well as an underrepresentation of pregnant women and children.

CONCLUSIONS

Rifamycin-containing regimens appear safer and at least as effective as isoniazid regimens in preventing TB and death and should be considered part of routine care in PLHIV. Knowledge gaps remain as to which specific rifamycin-containing regimen provides the optimal balance of efficacy, completion, and safety.

Infectious Diseases Learning Unit: Understanding Advances in the Treatment of Latent Tuberculosis Infection Among People With Human Immunodeficiency Virus

Tuberculosis (TB) remains the leading cause of death among people with human immunodeficiency virus (PWH). The diagnosis of latent TB infection (LTBI) and treatment with TB preventative therapy (TPT) can reduce morbidity and mortality in this population. Historically, isoniazid has been recommended for TPT in PWH due to the absence of drug-drug interactions with most antiretroviral therapy (ART). However, newer rifamycin-based regimens are safer, shorter in duration, associated with improved adherence, and may be as or more effective than isoniazid TPT. Current guidelines have significant heterogeneity in their recommendations for TPT regimens and acceptability of drug interactions with modern ART. In this Infectious Diseases learning unit, we review common questions on diagnosis, treatment, and drug interactions related to the management of LTBI among PWH.

Outcomes of isoniazid preventive therapy among people living with HIV in Kenya: A retrospective study of routine health care data

Introduction

Isoniazid preventive therapy (IPT) taken by People Living with HIV (PLHIV) protects against active tuberculosis (TB). Despite its recommendation, data is scarce on the uptake of IPT among PLHIV and factors associated with treatment outcomes. We aimed at determining the proportion of PLHIV initiated on IPT, assessed TB screening practices during and after IPT and IPT treatment outcomes.

Methods

A retrospective cohort study of a representative sample of PLHIV initiated on IPT between July 2015 and June 2018 in Kenya. For PLHIV initiated on IPT during the study period, we abstracted patient IPT uptake data from the National data warehouse. In contrast, we obtained information on socio-demographic, TB screening practices, IPT initiation, follow up, and outcomes from health facilities' patient record cards, IPT cards, and IPT registers. Further, we assessed baseline characteristics as potential correlates of developing active TB during and after treatment and IPT completion using multivariable logistic regression.

Results

From the data warehouse, 138,442 PLHIV were enrolled into ART during the study period and initiated 95,431 (68.9%) into IPT. We abstracted 4708 patients’ files initiated on IPT, out of which 3891(82.6%) had IPT treatment outcomes documented, 4356(92.5%) had ever screened for TB at every clinic visit, and 4,243(90.1%) had documentation of TB screening on the IPT tool before IPT initiation. 3712(95.4%) of patients with documented IPT treatment outcomes completed their treatment. 42(0.89%) of the abstracted patients developed active TB,16(38.1%) during, and 26(61.9%) after completing IPT. Follow up for active TB at 6-month post-IPT completion was done for 2729(73.5%) of patients with IPT treatment outcomes. Sex, Viral load suppression, and clinic type were associated with TB development (p<0.05). Levels 4, 5, FBO, and private facilities and IPT prescription practices were associated with IPT completion (p<0.05).

Conclusion

IPT initiation stands at two-thirds of the PLHIV, with a high completion rate. TB screening practices were better during IPT than after completion. Development of active TB during and after IPT emphasizes the need for a keen follow up.

Latent TB (LTBI) treatment: Challenges in India with an eye on 2025: "To Treat LTBI or not to treat, that is the question"

Latent tuberculosis infection (LTBI) is defined as a consistent immune response to Mycobacterium tuberculosis antigens without evidence of clinically evident active tuberculosis (TB). Diagnosis and treatment for LTBI are important for TB, especially in high-risk populations especially in high prevalent country like India. Tuberculin skin test (TST) and interferon-gamma release assays (IGRAs) are used to diagnose LTBI. Therefore an unequivocal policy /of diagnosis and treatment of LTBI will serve to ameliorate the standards of the Indian health scenario and bring the TB infection to the propinquity of its ultimate elimination.

Guidelines for the Treatment of Latent Tuberculosis Infection: Recommendations from the National Tuberculosis Controllers Association and CDC, 2020

Comprehensive guidelines for treatment of latent tuberculosis infection (LTBI) among persons living in the United States were last published in 2000 (American Thoracic Society. CDC targeted tuberculin testing and treatment of latent tuberculosis infection. Am J Respir Crit Care Med 2000;161:S221–47). Since then, several new regimens have been evaluated in clinical trials. To update previous guidelines, the National Tuberculosis Controllers Association (NTCA) and CDC convened a committee to conduct a systematic literature review and make new recommendations for the most effective and least toxic regimens for treatment of LTBI among persons who live in the United States.

The systematic literature review included clinical trials of regimens to treat LTBI. Quality of evidence (high, moderate, low, or very low) from clinical trial comparisons was appraised using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) criteria. In addition, a network meta-analysis evaluated regimens that had not been compared directly in clinical trials. The effectiveness outcome was tuberculosis disease; the toxicity outcome was hepatotoxicity. Strong GRADE recommendations required at least moderate evidence of effectiveness and that the desirable consequences outweighed the undesirable consequences in the majority of patients. Conditional GRADE recommendations were made when determination of whether desirable consequences outweighed undesirable consequences was uncertain (e.g., with low-quality evidence).

These updated 2020 LTBI treatment guidelines include the NTCA- and CDC-recommended treatment regimens that comprise three preferred rifamycin-based regimens and two alternative monotherapy regimens with daily isoniazid. All recommended treatment regimens are intended for persons infected with Mycobacterium tuberculosis that is presumed to be susceptible to isoniazid or rifampin. These updated guidelines do not apply when evidence is available that the infecting M. tuberculosis strain is resistant to both isoniazid and rifampin; recommendations for treating contacts exposed to multidrug-resistant tuberculosis were published in 2019 (Nahid P, Mase SR Migliori GB, et al. Treatment of drug-resistant tuberculosis. An official ATS/CDC/ERS/IDSA clinical practice guideline. Am J Respir Crit Care Med 2019;200:e93–e142). The three rifamycin-based preferred regimens are 3 months of once-weekly isoniazid plus rifapentine, 4 months of daily rifampin, or 3 months of daily isoniazid plus rifampin. Prescribing providers or pharmacists who are unfamiliar with rifampin and rifapentine might confuse the two drugs. They are not interchangeable, and caution should be taken to ensure that patients receive the correct medication for the intended regimen. Preference for these rifamycin-based regimens was made on the basis of effectiveness, safety, and high treatment completion rates. The two alternative treatment regimens are daily isoniazid for 6 or 9 months; isoniazid monotherapy is efficacious but has higher toxicity risk and lower treatment completion rates than shorter rifamycin-based regimens.

In summary, short-course (3- to 4-month) rifamycin-based treatment regimens are preferred over longer-course (6–9 month) isoniazid monotherapy for treatment of LTBI. These updated guidelines can be used by clinicians, public health officials, policymakers, health care organizations, and other state and local stakeholders who might need to adapt them to fit individual clinical circumstances.

Does Isoniazid Preventive Therapy Provide Better Treatment Outcomes in HIV-Infected Individuals in Northern Ethiopia? A Retrospective Cohort Study

Objectives

Early antiretroviral therapy (ART), isoniazid preventive therapy (IPT), and isoniazid-rifapentine (3HP) are effective strategies for preventing tuberculosis (TB) among people living with HIV (PLHIV). The study aimed to determine the effect of IPT on the TB incidence, follow-up CD4⁺ T cells, and all-cause mortality rate. Participants. Eligible patients on ART (n = 1, 863) were categorized into one-to-two ratios of exposed groups to IPT (n = 621) and nonexposed groups to IPT (n = 1, 242). Exposed groups entered the cohort at their first prescription of IPT, and unexposed groups entered into the study at the first prescription of ART and then followed until the occurrence of the outcome or date of administrative censoring (June 30, 2017). The outcome endpoints were TB incidence, follow-up CD4⁺ T cells, and all-cause mortality rate.

Results

The follow-up CD4⁺ T cells for the exposed and nonexposed groups were 405.74 and 366.95 cells/mm (World Health Organization (WHO), 2017), respectively, a statistically significant finding (t ₁₈₆₁ = -3.770, p < 0.0001; Cohen's d = 0.186). Nine percent of the exposed patients (620 incidence of TB per 100,000 person-years (PYs)) and 21.9% of the nonexposed patients (3160 incidence of TB per 100,000 PYs) developed TB. Mortality rate (per 100,000 PYs) was 440 for the exposed and 1490 for the unexposed patients. Statistically significant determinants of the all-cause mortality were unscheduled follow-up (AHR = 1.601; 95% CI: 1.154-2.222) and unable to work properly (AHR = 2.324; 95% CI: 1.643-3.288).

Conclusion

This study demonstrates the effect of IPT in reducing incidence of TB and all-cause mortality rate and improving follow-up CD4⁺ T cells. Promoting IPT use can help to achieve the TB eradicating national agenda in Ethiopia.

Seventy Years of Tuberculosis Prevention: Efficacy, Effectiveness, Toxicity, Durability, and Duration

Tuberculosis (TB) has been a leading infectious cause of death worldwide for much of human history, with 1.6 million deaths estimated in 2017. The Department of Epidemiology at the Johns Hopkins Bloomberg School of Public Health has played an important role in understanding and responding to TB, and it has made particularly substantial contributions to prevention of TB with chemoprophylaxis. TB preventive therapy is highly efficacious in the prevention of TB disease, yet it remains underutilized by TB programs worldwide despite strong evidence to support its use in high-risk groups, such as people living with HIV and household contacts, including those under 5 years of age. We review the evidence for TB preventive therapy and discuss the future of TB prevention.

Isoniazid Preventive Therapy for People With HIV Who Are Heavy Alcohol Drinkers in High TB-/HIV-Burden Countries: A Risk-Benefit Analysis

BACKGROUND

Isoniazid preventive therapy (IPT) reduces mortality among people living with HIV (PLHIV) and is recommended for those without active tuberculosis (TB) symptoms. Heavy alcohol use, however, is contraindicated for liver toxicity concerns. We evaluated the risks and benefits of IPT at antiretroviral therapy (ART) initiation to ART alone for PLHIV who are heavy drinkers in 3 high TB-/HIV-burden countries.

METHODS

We developed a Markov simulation model to compare ART alone to ART with either 6 or 36 months of IPT for heavy drinking PLHIV enrolling in care in Brazil, India, and Uganda. Outcomes included nonfatal toxicity, fatal toxicity, life expectancy, TB cases, and TB death.

RESULTS

In this simulation, 6 months of IPT + ART (IPT6) extended life expectancy over both ART alone and 36 months of IPT + ART (IPT36) in India and Uganda, but ART alone dominated in Brazil in 51.5% of simulations. Toxicity occurred in 160/1000 persons on IPT6 and 415/1000 persons on IPT36, with fatal toxicity in 8/1000 on IPT6 and 21/1000 on IPT36. Sensitivity analyses favored IPT6 in India and Uganda with high toxicity thresholds.

CONCLUSIONS

The benefits of IPT for heavy drinkers outweighed its risks in India and Uganda when given for a 6-month course. The toxicity/efficacy trade-off was less in Brazil where TB incidence is lower. IPT6 resulted in fatal toxicity in 8/1000 people, whereas even higher toxicities of IPT36 negated its benefits in all countries. Data to better characterize IPT toxicity among HIV-infected drinkers are needed to improve guidance.

Impact of isoniazid preventive therapy on the evaluation of long-term effectiveness of infant MVA85A vaccination

SETTING:

South Africa.

OBJECTIVE:

To evaluate the long-term effectiveness of infant modified vaccinia Ankara virus-expressing antigen 85A (MVA85A) vaccination against tuberculosis (TB).

DESIGN:

We analysed data from a double-blind randomised placebo-controlled Phase 2b MVA85A infant TB vaccine trial (2009–2012), with extended post-trial follow-up (2012–2014). Isoniazid preventive therapy (IPT) was provided by public health services according to national guidelines. The primary outcome was curative treatment for TB disease. Survival analysis and Poisson regression were used for study analysis.

RESULTS:

Total follow-up was 10 351 person-years of observation (pyo). Median follow-up age was 4.8 years (interquartile range 4.4–5.2). There were 328 (12%) TB cases. TB disease incidence was 3.2/100 pyo (95%CI 2.8–3.5) overall, and respectively 3.3 (95%CI 2.9–3.9) and 3.0 (95%CI 2.6–3.5)/100 pyo in the MVA85A vaccine and placebo arms. A total of 304 children (11%) received IPT, with respectively 880 and 9471 pyo among IPT and non-IPT recipients. There were 23 (7.6%) TB cases among 304 IPT recipients vs. 305 (12.9%) among 2374 non-IPT recipients (P = 0.008). IPT effectiveness was 85% (95%CI 76–91).

CONCLUSION:

Extended follow-up confirms no long-term effectiveness of infant MVA85A vaccination, but a six-fold reduction in TB risk can be attributed to IPT. National TB programmes in high TB burden countries should ensure optimal implementation of IPT for eligible children.

Effect of isoniazid preventive therapy on risk of death in west African, HIV-infected adults with high CD4 cell counts: long-term follow-up of the Temprano ANRS 12136 trial

BACKGROUND

Temprano ANRS 12136 was a factorial 2 × 2 trial that assessed the benefits of early antiretroviral therapy (ART; ie, in patients who had not reached the CD4 cell count threshold used to recommend starting ART, as per the WHO guidelines that were the standard during the study period) and 6-month isoniazid preventive therapy (IPT) in HIV-infected adults in Côte d'Ivoire. Early ART and IPT were shown to independently reduce the risk of severe morbidity at 30 months. Here, we present the efficacy of IPT in reducing mortality from the long-term follow-up of Temprano.

METHODS

For Temprano, participants were randomly assigned to four groups (deferred ART, deferred ART plus IPT, early ART, or early ART plus IPT). Participants who completed the trial follow-up were invited to participate in a post-trial phase. The primary post-trial phase endpoint was death, as analysed by the intention-to-treat principle. We used Cox proportional models to compare all-cause mortality between the IPT and no IPT strategies from inclusion in Temprano to the end of the follow-up period.

FINDINGS

Between March 18, 2008, and Jan 5, 2015, 2056 patients (mean baseline CD4 count 477 cells per μL) were followed up for 9404 patient-years (Temprano 4757; post-trial phase 4647). The median follow-up time was 4·9 years (IQR 3·3-5·8). 86 deaths were recorded (Temprano 47 deaths; post-trial phase 39 deaths), of which 34 were in patients randomly assigned IPT (6-year probability 4·1%, 95% CI 2·9-5·7) and 52 were in those randomly assigned no IPT (6·9%, 5·1-9·2). The hazard ratio of death in patients who had IPT compared with those who did not have IPT was 0·63 (95% CI, 0·41 to 0·97) after adjusting for the ART strategy (early vs deferred), and 0·61 (0·39-0·94) after adjustment for the ART strategy, baseline CD4 cell count, and other key characteristics. There was no evidence for statistical interaction between IPT and ART (p_interaction=0·77) or between IPT and time (p_interaction=0·94) on mortality.

INTERPRETATION

In Côte d'Ivoire, where the incidence of tuberculosis was last reported as 159 per 100 000 people, 6 months of IPT has a durable protective effect in reducing mortality in HIV-infected people, even in people with high CD4 cell counts and who have started ART.

FUNDING

National Research Agency on AIDS and Viral Hepatitis (ANRS).

Rifampicin resistance after treatment for latent tuberculous infection: a systematic review and meta-analysis

SETTING

Treatment for latent tuberculous infection (LTBI) reduces the risk of tuberculosis (TB) disease. Shorter, rifamycin-containing regimens have been shown to be as effective as 6 months of isoniazid and superior with regard to safety and completion rate. It is unknown whether preventive therapy with rifamycins increases resistance to the drugs used.

OBJECTIVE

To determine whether treatment for LTBI with rifamycin-containing regimens leads to significant development of resistance against rifamycins.

DESIGN

Systematic review and meta-analysis.

RESULTS

We included six randomised-controlled trials of rifamycin-containing regimens for LTBI treatment that reported drug resistance. There was no statistically significant increased risk of rifamycin resistance after LTBI treatment with rifamycin-containing regimens compared to non-rifamycin-containing regimens (RR 3.45, 95%CI 0.72-16.56; P = 0.12) or placebo (RR 0.20, 95%CI 0.02-1.66; P = 0.13).

CONCLUSION

Preventive treatment with rifamycin-containing regimens does not significantly increase rifamycin resistance. Programmatic management of LTBI requires the creation of sound surveillance systems to monitor drug resistance.

Adherence, tolerability, and outcome after 36 months of isoniazid-preventive therapy in 2 rural clinics of Swaziland: A prospective observational feasibility study

Although efficacy of 36 months isoniazid preventive therapy (IPT) among HIV-positive individuals has been proven in trial settings, outcome, tolerance, and adherence have rarely been evaluated in real-life settings.This is a prospective observational cohort study conducted in 2 primary care rural clinics in Swaziland.After negative tuberculosis symptom screening, patients either with the positive tuberculin skin test (TST) or after tuberculosis treatment were initiated on IPT for 144 weeks. In addition to routine clinic visits, adherence was assessed every semester.Of 288 eligible patients, 2 patients never started IPT (1 refusal, 1 contraindication), and 253 (87.8%), 234 (81.3%), and 228 (79.2%) were still on IPT after 48, 96, and 144 weeks, respectively (chiP = .01). Of 41 patients who interrupted IPT before 144 weeks, 21 defaulted (of which 17 also defaulted HIV care); 16 stopped because of adverse drug reactions; 2 were discontinued by clinicians' mistake and 1 because of TB symptoms. Five patients (1.7%) died of causes not related to IPT, 5 (1.7%) developed TB of which 2 were isoniazid-resistant, and 9 (3.1%) were transferred to another clinic. As an indicator of adherence, isoniazid could be detected in the urine during 86.3% (302/350) and 73.6% (248/337) of patient visits in the 2 clinics, respectively (chiP < .001).The routine implementation of IPT 36 months was feasible and good patient outcomes were achieved, with low TB incidence, good tolerance, and sustained adherence.

Mycobacterium bovis BCG and New Vaccines for the Prevention of Tuberculosis

Tuberculosis infects millions of people worldwide and remains a leading global killer despite widespread neonatal administration of the tuberculosis vaccine, bacillus Calmette-Guérin (BCG). BCG has clear and sustained efficacy, but after 10 years, its efficacy appears to wane, at least in some populations. Fortunately, there are many new tuberculosis vaccines in development today, some in advanced stages of clinical trial testing. Here we review the epidemiological need for tuberculosis vaccination, including evolving standards for administration to at risk individuals in developing countries. We also examine proven sources of immune protection from tuberculosis, which to date have exclusively involved natural or vaccine exposure to whole cell mycobacteria. After summarizing evidence for the use and efficacy of BCG, we detail the most promising new candidate vaccines against tuberculosis. The global need for a new tuberculosis vaccine is acute and huge, but clinical trials to be completed in the coming few years are likely either to identify a new tuberculosis vaccine or to substantially reframe how we understand immune protection from this historical scourge.

Is systematic screening and treatment for latent tuberculosis infection in HIV patients useful in a low endemic setting?

OBJECTIVES

A decreasing incidence of tuberculosis (TB) among HIV patients has been documented in high-income settings and screening for tuberculosis is not systematically performed in many clinics (such as ours). Our objectives are to evaluate whether a same decline of incidence was seen in our Belgian tertiary center and to evaluate whether systematic screening and prophylaxis of tuberculosis should remain part of routine practice.

METHODS

Between 2005 and 2012, the annual incidence of tuberculosis among adult HIV patients was measured. The impact of demographic characteristics and CD₄ nadir on the incidence of active TB was evaluated.

RESULTS

Among the 1167 patients who entered the cohort, 42 developed active TB with a significant decrease of annual incidence from 28/1000 patient-years in 2005 to 3/1000 patient-years in 2012. Among the 42 cases, 83% were of sub-Saharan origin. Median CD4 cell count upon HIV diagnosis was significantly lower in TB cases and 60% had a nadir CD4 below 200/μl. Thirty-six percent of incident TB occurred within 14 days after HIV diagnosis.

CONCLUSION

A significant decline of TB incidence in HIV patients was observed. Incident TB occurred mainly in African patients, with low CD4 upon HIV diagnosis. A significant proportion of TB cases were discovered early in follow-up which probably reflects TB already present upon HIV diagnosis. In a low endemic setting, exclusion of active TB upon HIV diagnosis remains a priority and screening for LTBI should focus on HIV patients from high risk groups such as migrants from endemic regions, especially in patients with low CD4 nadir.

Efficacy and completion rates of rifapentine and isoniazid (3HP) compared to other treatment regimens for latent tuberculosis infection: a systematic review with network meta-analyses

BACKGROUND

We conducted a systematic review and network meta-analysis (NMA) to examine the efficacy and completion rates of treatments for latent tuberculosis infection (LTBI). While a previous review found newer, short-duration regimens to be effective, several included studies did not confirm LTBI, and analyses did not account for variable follow-up or assess completion.

METHODS

We searched MEDLINE, Embase, CENTRAL, PubMed, and additional sources to identify RCTs in patients with confirmed LTBI that involved a regimen of interest and reported on efficacy or completion. Regimens of interest included isoniazid (INH) with rifapentine once weekly for 12 weeks (INH/RPT-3), 6 and 9 months of daily INH (INH-6; INH-9), 3-4 months daily INH plus rifampicin (INH/RFMP 3-4), and 4 months daily rifampicin alone (RFMP-4). NMAs were performed to compare regimens for both endpoints.

RESULTS

Sixteen RCTs (n = 44,149) and 14 RCTs (n = 44,128) were included in analyses of efficacy and completion. Studies were published between 1968 and 2015, and there was diversity in patient age and comorbidities. All regimens of interest except INH-9 showed significant benefits in preventing active TB compared to placebo. Comparisons between active regimens did not reveal significant differences. While definitions of regimen completion varied across studies, regimens of 3-4 months were associated with a greater likelihood of adequate completion.

CONCLUSIONS

Most of the active regimens showed an ability to reduce the risk of active TB relative to no treatment, however important differences between active regimens were not found. Shorter rifamycin-based regimens may offer comparable benefits to longer INH regimens. Regimens of 3-4 months duration are more likely to be completed than longer regimens.

Benefits of continuous isoniazid preventive therapy may outweigh resistance risks in a declining tuberculosis/HIV coepidemic

OBJECTIVE

Extending the duration of isoniazid preventive therapy (IPT) among people living with HIV (PLHIV) may improve its effectiveness at both individual and population levels, but could also increase selective pressure in favor of isoniazid-resistant tuberculosis (TB) strains. The objective of this study was to determine the relative importance of these two effects.

METHODS

Transmission dynamic model.

DESIGN

We created a mathematical model of TB transmission incorporating HIV incidence and treatment, mixed strain latent TB infections, and four different phenotypes of TB drug resistance (pan-susceptible, isoniazid monoresistant, rifampicin monoresistant, and multidrug resistant). We used this model to project the effects of IPT duration on the incidence of isoniazid-sensitive and isoniazid-resistant TB as well as mortality among PLHIV. We evaluated the sensitivity of our baseline model, which was calibrated to data from Botswana, to different assumptions about the future trajectory of the TB epidemic.

RESULTS

Our model suggests that, in the context of a declining TB epidemic such as that currently observed in Botswana, the incidence and mortality benefits of continuous IPT for PLHIV are likely to outweigh the potential resistance risks associated with long-duration IPT. However, should TB epidemics fail to remain in control, as was observed during the initial emergence of HIV, the selective pressure imposed by widespread use of continuous IPT on isoniazid-resistant TB incidence may erode its initial benefits.

CONCLUSION

Resistance concerns are likely insufficient to rule out use of continuous IPT when coupled with effective TB treatment, case finding, and HIV control.

Post-treatment effect of isoniazid preventive therapy on tuberculosis incidence in HIV-infected individuals on antiretroviral therapy

BACKGROUND

In HIV-uninfected individuals, isoniazid preventive therapy (IPT) has been associated with long-term protection against tuberculosis (TB). For HIV-infected/antiretroviral therapy (ART)-naive individuals, high TB rates have been observed following completion of IPT, consistent with a lack of 'cure' of infection. Recent trial data of IPT among HIV-infected individuals on ART in Khayelitsha, South Africa, have suggested that the effect of IPT persisted following completion of IPT.

METHODS

Using mathematical modelling, we explored if this increased duration of protection may be due to an increased curative ability of IPT when given in combination with ART. The model was used to estimate the annual risk of infection and proportion of individuals whose latent infection was 'cured' by IPT, defined such that they must be reinfected to be at risk of disease.

RESULTS

The estimated annual risk of infection was 4.0% (2.6-5.8) and the estimated proportion of individuals whose latent Mycobacterium tuberculosis infection was cured following IPT was 35.4% (2.4-76.4), higher than that previously estimated for HIV-infected/ART-naive individuals. Our results suggest that IPT can cure latent M. tuberculosis infection in approximately one-third of HIV-infected individuals on ART and therefore provide protection beyond the period of treatment.

CONCLUSION

Among HIV-infected individuals on ART in low incidence settings, 12 months of IPT may provide additional long-term benefit. Among HIV-infected individuals on ART in high incidence settings, the durability of this protection will be limited because of continued risk of reinfection, and continuous preventive therapy together with improved infection control efforts will be required to provide long-term protection against TB.

The timing of tuberculosis after isoniazid preventive therapy among gold miners in South Africa: a prospective cohort study

BACKGROUND

The durability of isoniazid preventive therapy (IPT) in preventing tuberculosis (TB) is limited in high-prevalence settings. The underlying mechanism (reactivation of persistent latent TB or reinfection) is not known. We aimed to investigate the timing of TB incidence during and after IPT and associated risk factors in a very high TB and HIV-prevalence setting, and to compare the observed rate with a modelled estimate of TB incidence rate after IPT due to reinfection.

METHODS

In a post-hoc analysis of a cluster-randomized trial of community-wide IPT among South African gold miners, all intervention arm participants that were dispensed IPT for at least one of the intended 9 months were included. An incident TB case was defined as any participant with a positive sputum smear or culture, or with a clinical TB diagnosis assigned by a senior study clinician. Crude TB incidence rates were calculated during and after IPT, overall and by follow-up time. HIV status was not available. Multivariable Cox regression was used to analyse risk factors by follow-up time after IPT. Estimates from a published mathematical model of trial data were used to calculate the average reinfection TB incidence in the first year after IPT.

RESULTS

Among 18,520 participants (96% male, mean age 41 years, median follow-up 2.1 years), 708 developed TB. The TB incidence rate during the intended IPT period was 1.3/100 person-years (pyrs; 95% confidence interval (CI), 1.0-1.6) and afterwards 2.3/100 pyrs (95% CI, 1.9-2.7). TB incidence increased within 6 months followed by a stable rate over time. There was no evidence for changing risk factors for TB disease over time after miners stopped IPT. The average TB incidence rate attributable to reinfection in the first year was estimated at 1.3/100 pyrs, compared to an observed rate of 2.2/100 pyrs (95% CI, 1.8-2.7).

CONCLUSIONS

The durability of protection by IPT was lost within 6-12 months in this setting with a high HIV prevalence and a high annual risk of M. tuberculosis infection. The observed rate was higher than the modelled rate, suggesting that reactivation of persistent latent infection played a role in the rapid return to baseline TB incidence.

Implementation and Operational Research: Cost-Effectiveness of Antiretroviral Therapy and Isoniazid Prophylaxis to Reduce Tuberculosis and Death in People Living With HIV in Botswana

OBJECTIVE

In Botswana, a 36-month course of isoniazid treatment of latent tuberculosis (TB) infection [isoniazid preventive therapy (IPT)] was superior to 6-month IPT in reducing TB and death in persons living with HIV (PLHIV), having positive tuberculin skin tests (TSTs) but not in those with negative TST. We examined the cost-effectiveness of IPT in Botswana, where antiretroviral therapy (ART) is widely available.

DESIGN

Using a decision-analytic model, we determined the incremental cost-effectiveness of strategies for reducing TB and death in 10,000 PLHIV over 36 months.

METHODS

IPT for 6 months and provision of ART if CD4 lymphocyte count <250 cells per microliter (2011 Botswana policy) was compared with 6 alternative strategies that varied the use of IPT, TST, and ART for CD4 count thresholds, including CD4 <350 and <500 cells per microliter.

RESULTS

Botswana policy, 2011 was dominated by most other strategies. IPT of 36 months for TST-positive PLHIV with ART for CD4 <250 cells per microliter resulted in 120 fewer TB cases for an additional cost of $1612 per case averted and resulted in 80 fewer deaths for an additional $2418 per death averted compared with provision of 6-month IPT to TST-positive PLHIV who received ART for CD4 <250 cells per microliter, the next most effective strategy. Alternative strategies offered lower incremental effectiveness at higher cost. These findings remained consistent in sensitivity analyses.

CONCLUSIONS

A strategy of treating PLHIV who have positive TST with 36-month IPT is more cost effective for reducing both TB and death compared with providing IPT without a TST, providing only 6-month IPT, or expanding ART eligibility without IPT.

Effect of isoniazid preventive therapy on immune responses to mycobacterium tuberculosis: an open label randomised, controlled, exploratory study

BACKGROUND

With the renewed emphasis to implement isoniazid preventive therapy (IPT) in Sub-Saharan Africa, we investigated the effect of IPT on immunological profiles among household contacts with latent tuberculosis.

METHODS

Household contacts of confirmed tuberculosis patients were tested for latent tuberculosis using the QuantiFERON®-TB Gold In-Tube (QFN) assay and tuberculin skin test (TST). HIV negative contacts aged above 5 years, positive to both QFN and TST, were randomly assigned to IPT and monthly visits or monthly visits only. QFN culture supernatants from enrolment and six months' follow-up were analysed for M.tb-specific Th1, Th2, Th17, and regulatory cytokines by Luminex assay, and for M.tb-specific IgG antibody concentrations by ELISA. Effects of IPT were assessed as the net cytokine and antibody production at the end of six months.

RESULTS

Sixteen percent of contacts investigated (47/291) were randomised to IPT (n = 24) or no IPT (n = 23). After adjusting for baseline cytokine or antibody responses, and for presence of a BCG scar, IPT (compared to no IPT) resulted in a relative decline in M.tb-specific production of IFN gamma (adjusted mean difference at the end of six months (bootstrap 95% confidence interval (CI), p-value) -1488.6 pg/ml ((-2682.5, -294.8), p = 0.01), and IL- 2 (-213.1 pg/ml (-419.2, -7.0), p = 0.04). A similar decline was found in anti-CFP-10 antibody levels (adjusted geometric mean ratio (bootstrap 95% CI), p-value) 0.58 ((0.35, 0.98), p = 0.04). We found no effect on M.tb-specific Th2 or regulatory or Th17 cytokine responses, or on antibody concentrations to PPD and ESAT-6.

CONCLUSIONS

IPT led to a decrease in Th1 cytokine production, and also in the anti CFP-10 antibody concentration. This could be secondary to a reduction in mycobacterial burden or as a possible direct effect of isoniazid induced T cell apoptosis, and may have implications for protective immunity following IPT in tuberculosis-endemic countries.

TRIAL REGISTRATION

ISRCTN registry, ISRCTN15705625. Registered on 30(th) September 2015.

Isoniazid-associated hepatitis in adults infected with HIV receiving 36 months of isoniazid prophylaxis in Botswana

BACKGROUND

The World Health Organization recommends 36 months of isoniazid preventive therapy (36IPT) for adults infected with HIV living in TB-endemic countries. We determined the rates and risk factors for isoniazid-associated hepatitis with the use of 36IPT.

METHODS

One thousand six adults infected with HIV received 36IPT during a pragmatic randomized trial set in Botswana public health clinics providing HIV care. Enrollment exclusion criteria included jaundice or elevations of serum transaminases (ESTs) > 2.5-fold the upper limit of normal (ULN). Participants with any CD4+ lymphocyte count were eligible and received antiretroviral therapy (ART) when CD4+ < 200 cells/μL. 36IPT was stopped for severe hepatitis (more than fivefold ULN EST) but not for moderate hepatitis (2.5-fold to fivefold ULN EST).

RESULTS

Pharmacy refill records showed 2,237 person-years of isoniazid receipt; 48% of participants initiated ART by 36 months. A total of 1.9% (19 of 1,006) of participants were diagnosed with severe hepatitis; three had jaundice and two of these developed hepatic encephalopathy. Another 3.1% (31 of 1,006) of participants experienced moderate hepatitis. Thirty-eight percent (19 of 50) of participants with moderate to severe hepatitis concomitantly received ART. Forty percent (20 of 50) of moderate to severe cases occurred within the first 2 months of IPT and during this period were not associated with receipt of ART at baseline (hazard ratio, 1.49; 95% CI, 0.20-11.1; P = .70).

CONCLUSIONS

Adults infected with HIV receiving 36IPT did not have an increased incidence of moderate to severe hepatitis or hepatic encephalopathy compared with published reports among people infected with HIV, people not infected with HIV in trials or public health programs. Compared with participants not receiving ART, the risk of moderate to severe hepatitis was not increased by ART.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT00164281; URL: www.clinicaltrials.gov.

Use of isoniazid preventive therapy for tuberculosis prophylaxis among people living with HIV/AIDS: a review of the literature

BACKGROUND

Tuberculosis (TB) is the leading preventable cause of death in persons living with HIV (PLHIV), accounting for over a quarter of all HIV-associated deaths in 2012. Isoniazid preventive therapy (IPT) has the potential to decrease TB-related cases and deaths in PLHIV; however, implementation of this has been slow in many high HIV- and TB-burden settings.

METHODOLOGY

We performed an assessment of the evidence for the use of IPT in adults living with HIV based on a review of the literature published from 1995 to 2013. Eligible articles included data on mortality, morbidity, or retention in care related to the provision of IPT to adults with HIV in low- or middle-income countries. Cost-effectiveness information was also abstracted.

RESULTS

We identified 41 articles involving over 45,000 PLHIV. While there was little evidence to demonstrate that IPT reduced mortality in PLHIV, there was substantial evidence that IPT reduced TB incidence. While these findings were consistent irrespective of CD4 or antiretroviral therapy status, studies frequently demonstrated a greater benefit among patients with a positive TB skin test (TST). Duration of effectiveness and benefits of prolonged therapy varied across settings.

CONCLUSIONS

This analysis supports World Health Organization recommendations for the provision of IPT to PLHIV to reduce TB-associated morbidity and serves to highlight the need to strengthen IPT implementation. While there appears to be a greater benefit of IPT among PLHIV who are TST positive, IPT should be provided to all PLHIV without presumptive TB when TST is not available.

Tuberculosis control in South African gold mines: mathematical modeling of a trial of community-wide isoniazid preventive therapy

A recent major cluster randomized trial of screening, active disease treatment, and mass isoniazid preventive therapy for 9 months during 2006-2011 among South African gold miners showed reduced individual-level tuberculosis incidence but no detectable population-level impact. We fitted a dynamic mathematical model to trial data and explored 1) factors contributing to the lack of population-level impact, 2) the best-achievable impact if all implementation characteristics were increased to the highest level achieved during the trial ("optimized intervention"), and 3) how tuberculosis might be better controlled with additional interventions (improving diagnostics, reducing treatment delay, providing isoniazid preventive therapy continuously to human immunodeficiency virus-positive people, or scaling up antiretroviral treatment coverage) individually and in combination. We found the following: 1) The model suggests that a small proportion of latent infections among human immunodeficiency virus-positive people were cured, which could have been a key factor explaining the lack of detectable population-level impact. 2) The optimized implementation increased impact by only 10%. 3) Implementing additional interventions individually and in combination led to up to 30% and 75% reductions, respectively, in tuberculosis incidence after 10 years. Tuberculosis control requires a combination prevention approach, including health systems strengthening to minimize treatment delay, improving diagnostics, increased antiretroviral treatment coverage, and effective preventive treatment regimens.

[Fight against tuberculosis in the world]

Tuberculosis (TB) in a major health problem in the world. WHO and its partners especially, the stop TB partnership launched numerous strategies against TB especially in the 1990. Strategy DOTS (directly observed therapy short course) was launched in 1995. One main key was the direct supervision of drug intake by patients. Progress was achieved but it was insufficient. A new strategy called "Stop TB Strategy 2006-2015" was launched in 2006 in the context of Millennium Development Goals (MDG) elaborated by United Nations. The common goals were to halt and start to reverse the incidence of TB, reduce the prevalence and death rate by 50% compared to their level in 1990 by 2015 to eliminate TB as a public health problem by 2050. The end of 2010 marks the mid-point of the Global Plan and is an obvious time to update it and take into account actual progress with a focus on the 2015 to reach goals. So an updated Global Plan to stop TB 2011-2015, was launched. Expected progress and targets were defined for 2015, in diagnosis and treatment, in co-infection TB/HIV, in drug-resistant TB and achievements expected in new tests for diagnosis, new medications, new vaccines and new regimens with shorter duration of treatment. WHO and partners have started discussions to define the new post 2015 strategy to TB control and elimination. Risk factors (diabetes, malnutrition, tobacco smoke…) and socioeconomic factors, which are associated with TB, should be included in the new strategy to eliminate TB in 2050.

Tuberculosis incidence after 36 months' isoniazid prophylaxis in HIV-infected adults in Botswana: a posttrial observational analysis

OBJECTIVE

Thirty-six months of isoniazid preventive therapy (36IPT) was superior to 6 months of IPT (6IPT) in preventing tuberculosis (TB) among HIV-infected adults in Botswana. We assessed the posttrial durability of this benefit.

DESIGN

A 36-month double-blind placebo controlled trial (1 : 1 randomization) with recruitment between November 2004 and July 2006 and observation until June 2011.

METHODS

One thousand, nine hundred and ninety-five participants were followed in eight public health clinics. Twenty-four percent had a tuberculin skin test ≥5 mm (TST-positive). A minimum CD4 lymphocyte count was not required for enrolment. Antiretroviral therapy (ART) was provided in accordance with Botswana guidelines; 72% of participants retained by June 2011 had initiated ART. Multivariable analysis using Cox regression analysis included treatment arm, TST status, ART as a time-dependent variable and CD4 cell count at baseline and updated at 36 months.

RESULTS

In the posttrial period, 2.13 and 2.14 per 100 person-years accumulated, whereas 0.93 and 1.13% TB incidence rates were observed in the 36IPT and 6IPT arms, respectively (P = 0.52). The crude hazard ratio of TB during the trial and posttrial was 0.57 [95% confidence intervals (CI) 0.33, 0.99] and 0.82 (95% CI 0.46, 1.49), and when restricted to TST-positive participants was 0.26 (95% CI 0.08, 0.80) and 0.40 (95% CI 0.15, 1.08), respectively. Multivariable analysis showed that ART use was associated with reduced death (adjusted hazard ratio 0.36, 95% CI 0.17-0.75) but not TB (0.92, 95% CI 0.55-1.53) in the posttrial period.

CONCLUSION

The benefit of 36IPT for TB prevention declined posttrial in this cohort. Adjunctive measures are warranted to prevent TB among HIV-infected persons receiving long-term ART in TB-endemic settings.

Long-term protection from isoniazid preventive therapy for tuberculosis in HIV-infected patients in a medium-burden tuberculosis setting: the TB/HIV in Rio (THRio) study

BACKGROUND

The duration of protection against tuberculosis provided by isoniazid preventive therapy is not known for human immunodeficiency virus (HIV)-infected individuals living in settings of medium tuberculosis incidence.

METHODS

We conducted an individual-level analysis of participants in a cluster-randomized, phased-implementation trial of isoniazid preventive therapy. HIV-infected patients who had positive tuberculin skin tests (TSTs) were followed until tuberculosis diagnosis, death, or administrative censoring. Nelson-Aalen cumulative hazard plots were generated and hazards were compared using the log-rank test. Cox proportional hazards models were fitted to investigate factors associated with tuberculosis diagnosis.

RESULTS

Between 2003 and 2009, 1954 patients with a positive TST were studied. Among these, 1601 (82%) initiated isoniazid. Overall tuberculosis incidence was 1.39 per 100 person-years (PY); 0.53 per 100 PY in those who initiated isoniazid and 6.52 per 100 PY for those who did not (adjusted hazard ratio [aHR], 0.17; 95% confidence interval [CI], .11-.25). Receiving antiretroviral therapy at time of a positive TST was associated with a reduced risk of tuberculosis (aHR, 0.69; 95% CI, .48-1.00). Nelson-Aalen plots of tuberculosis incidence showed a constant risk, with no acceleration in 7 years of follow-up for those initiating isoniazid preventive therapy.

CONCLUSIONS

Isoniazid preventive therapy significantly reduced tuberculosis risk among HIV-infected patients with a positive TST. In a medium-prevalence setting, 6 months of isoniazid in HIV-infected patients with positive TST reduces tuberculosis risk over 7 years of follow-up, in contrast to results of studies in higher-burden settings in Africa.

Isoniazid plus antiretroviral therapy to prevent tuberculosis: a randomised double-blind, placebo-controlled trial

BACKGROUND

Antiretroviral therapy reduces the risk of tuberculosis, but tuberculosis is more common in people with HIV than in people without HIV. We aimed to assess the effect of isoniazid preventive therapy on the risk of tuberculosis in people infected with HIV-1 concurrently receiving antiretroviral therapy.

METHODS

For this pragmatic randomised double-blind, placebo-controlled trial in Khayelitsha, South Africa, we randomly assigned (1:1) patients to receive either isoniazid preventive therapy or a placebo for 12 months (could be completed during 15 months). Randomisation was done with random number generator software. Participants, physicians, and pharmacy staff were masked to group assignment. The primary endpoint was time to development of incident tuberculosis (definite, probable, or possible). We excluded tuberculosis at screening by sputum culture. We did a modified intention-to-treat analysis and excluded all patients randomly assigned to groups who withdrew before receiving study drug or whose baseline sputum culture results suggested prevalent tuberculosis. This study is registered with ClinicalTrials.gov, number NCT00463086.

FINDINGS

1329 participants were randomly assigned to receive isoniazid preventive therapy (n=662) or placebo (n=667) between Jan 31, 2008, and Sept 31, 2011, and contributed 3227 person-years of follow-up to the analysis. We recorded 95 incident cases of tuberculosis; 37 were in the isoniazid preventive therapy group (2·3 per 100 person-years, 95% CI 1·6-3·1), and 58 in the placebo group (3·6 per 100 person-years, 2·8-4·7; hazard ratio [HR] 0·63, 95% CI 0·41-0·94). Study drug was discontinued because of grade 3 or 4 raised alanine transaminase concentrations in 19 of 662 individuals in the isoniazid preventive therapy group and ten of the 667 individuals in the placebo group (risk ratio 1·9, 95% CI 0·90-4·09). We noted no evidence that the effect of isoniazid preventive therapy was restricted to patients who were positive on tuberculin skin test or interferon gamma release assay (adjusted HR for patients with negative tests 0·43 [0·21-0·86] and 0·43 [0·20-0·96]; for positive tests 0·86 [0·37-2·00] and 0·55 [0·26-1·24], respectively).

INTERPRETATION

Without a more predictive test or a multivariate algorithm that predicts benefit, isoniazid preventive therapy should be recommended to all patients receiving antiretroviral therapy in moderate or high incidence areas irrespective of tuberculin skin test or interferon gamma release assay status.

FUNDING

Department of Health of South Africa, the Wellcome Trust, Médecins Sans Frontières, European and Developing Countries Clinical Trials Partnership, Foundation for Innovation and New Diagnostics, the European Union, and Hasso Plattner (Institute of Infectious Diseases and Molecular Medicine, University of Cape Town).

Management of tuberculosis and latent tuberculosis infection in human immunodeficiency virus-infected persons

The syndemic of human immunodeficiency virus (HIV)/tuberculosis (TB) co-infection has grown as a result of the considerable sociogeographic overlaps between the two epidemics. The situation is particularly worrisome in countries with high or intermediate TB burden against the background of a variable HIV epidemic state. Early diagnosis of TB disease in an HIV-infected person is paramount but suffers from lack of sensitive and specific diagnostic tools. Enhanced symptom screening is currently advocated, and the wide application of affordable molecular diagnostics is urgently needed. Treatment of TB/HIV co-infection involves the concurrent use of standard antiretrovirals and antimycobacterials during which harmful drug interaction may occur. The pharmacokinetic interaction between rifamycin and antiretrovirals is a case in point, requiring dosage adjustment and preferential use of rifabutin, if available. Early initiation of antiretroviral therapy is indicated, preferably at 2 weeks after starting TB treatment for patients with a CD4 of <50 cells/μL. Development of TB-immune reconstitution inflammatory syndrome (TB-IRIS) is however more frequent with early antiretroviral therapy. The diagnosis of TB-IRIS is another clinical challenge, and cautious use of corticosteroids is suggested to improve clinical outcome. As a preventive measure against active TB disease, the screening for latent TB infection should be widely practiced, followed by at least 6-9 months of isoniazid treatment. To date tuberculin skin test remains the only diagnostic tool in high TB burden countries. The role of alternative tests, for example, interferon-γ release assay, would need to be better defined for clinical application.

Ability of preventive therapy to cure latent Mycobacterium tuberculosis infection in HIV-infected individuals in high-burden settings

Trials of isoniazid preventive therapy (IPT) for people living with HIV in southern Africa have shown high rates of tuberculosis disease immediately after cessation of therapy. This could be due to the lack of cure following preventive therapy or reinfection with rapid progression to disease. Using a model fitted to trial data, we estimate the degree to which preventive therapies cure latent Mycobacterium tuberculosis infection in HIV-infected individuals in high-tuberculosis-burden settings. We identified randomized controlled trials that compared IPT to placebo or alternative regimen in HIV-positive, tuberculin skin test positive individuals. A mathematical model describing tuberculosis transmission in a closed cohort of HIV-positive, M. tuberculosis infected, antiretroviral therapy naive individuals following completion of preventive therapy (or placebo) was fitted to posttherapy tuberculosis rates to estimate the annual risk of M. tuberculosis reinfection and the proportion of individuals whose latent infection was cured after therapy. Three trials met our inclusion criteria. Estimated annual risks of reinfection ranged between 3.7 and 4.9%. Our results suggest 6 mo of isoniazid cured in a small proportion [estimated proportion cured = 0% (interquartile range 0-30.9%)]. The proportion cured for 3-mo regimens containing rifampicin or rifapentine was 19-100%. IPT alone does not cure existing infections in the majority of HIV-infected individuals. In high-incidence settings, continuous IPT should be integrated with HIV care. Where the risk of reinfection is lower, preventive therapy with more curative drugs should be preferred for HIV-positive individuals to achieve durable patient benefit.

Aspiring to zero tuberculosis deaths among southern Africa's miners: is there a way forward?

Tuberculosis notification rates among South African miners range from 4,000 to 7,000 per 100,000 people. These rates far exceed national tuberculosis notification rates for the general population. Tuberculosis mortality also surpasses deaths caused by mining accidents. These extraordinarily high rates of disease are unambiguously linked to a series of contributing factors, including exposure to silica dust, HIV infection, and poor working and living conditions. We argue that the only way to stop the transmission of this airborne disease is to treat the mine and its living quarters as one should any other congregate setting with individuals who have high rates of infection with drug-susceptible and drug-resistant strains of tuberculosis. This means implementing interventions that have been demonstrated to stop the spread of tuberculosis over the last 60 years: immediate treatment of active tuberculosis, concurrent treatment of latent tuberculosis disease to reduce the burden of active cases, and appropriate management of patients infected with HIV. Because tuberculosis is also a social disease, biomedical interventions must be coupled with improved living and working conditions. Achieving zero deaths from tuberculosis in the mines is possible if a clear commitment is made to a strategy that recognizes and ameliorates the biological and social antecedents to this epidemic.

A trial of mass isoniazid preventive therapy for tuberculosis control

BACKGROUND

Tuberculosis is epidemic among workers in South African gold mines. We evaluated an intervention to interrupt tuberculosis transmission by means of mass screening that was linked to treatment for active disease or latent infection.

METHODS

In a cluster-randomized study, we designated 15 clusters with 78,744 miners as either intervention clusters (40,981 miners in 8 clusters) or control clusters (37,763 miners in 7 clusters). In the intervention clusters, all miners were offered tuberculosis screening. If active tuberculosis was diagnosed, they were referred for treatment; if not, they were offered 9 months of isoniazid preventive therapy. The primary outcome was the cluster-level incidence of tuberculosis during the 12 months after the intervention ended. Secondary outcomes included tuberculosis prevalence at study completion.

RESULTS

In the intervention clusters, 27,126 miners (66.2%) underwent screening. Of these miners, 23,659 (87.2%) started taking isoniazid, and isoniazid was dispensed for 6 months or more to 35 to 79% of miners, depending on the cluster. The intervention did not reduce the incidence of tuberculosis, with rates of 3.02 per 100 person-years in the intervention clusters and 2.95 per 100 person-years in the control clusters (rate ratio in the intervention clusters, 1.00; 95% confidence interval [CI], 0.75 to 1.34; P=0.98; adjusted rate ratio, 0.96; 95% CI, 0.76 to 1.21; P=0.71), or the prevalence of tuberculosis (2.35% vs. 2.14%; adjusted prevalence ratio, 0.98; 95% CI, 0.65 to 1.48; P=0.90). Analysis of the direct effect of isoniazid in 10,909 miners showed a reduced incidence of tuberculosis during treatment (1.10 cases per 100 person-years among miners receiving isoniazid vs. 2.91 cases per 100 person-years among controls; adjusted rate ratio, 0.42; 95% CI, 0.20 to 0.88; P=0.03), but there was a subsequent rapid loss of protection.

CONCLUSIONS

Mass screening and treatment for latent tuberculosis had no significant effect on tuberculosis control in South African gold mines, despite the successful use of isoniazid in preventing tuberculosis during treatment. (Funded by the Consortium to Respond Effectively to the AIDS TB Epidemic and others; Thibela TB Current Controlled Trials number, ISRCTN63327174.).

Diagnosis and treatment of latent tuberculosis infection: an update

It is estimated that more than two billion people have latent M. tuberculosis infection, and this population serves as an important reservoir for future tuberculosis cases. Prevalence estimates are limited by difficulties in diagnosing the infection, including the lack of an ideal test, and an incomplete understanding of latency. Current tests include the tuberculin skin test and two interferon-γ release assays: QuantiFERON Gold In-Tube and T-SPOT.TB. This update focuses on recent publications regarding the ability of these tests to predict tuberculosis disease, their reproducibility over serial tests, and discordance between tests. We also discuss recent advances in the treatment of latent M. tuberculosis infection, including the three-month regimen of once-weekly rifapentine plus isoniazid, and prolonged isoniazid therapy for HIV-infected persons living in high-tuberculosis-incidence settings. We provide an update on the tolerability of the three-month regimen.

Efficacy of a six-month versus a 36-month regimen for prevention of tuberculosis in HIV-infected persons in India: a randomized clinical trial

Background

The optimal duration of preventive therapy for tuberculosis (TB) among HIV-infected persons in TB-endemic countries is unknown.

Methods

An open-label randomized clinical trial was performed and analyzed for equivalence. Seven hundred and twelve HIV-infected, ART-naïve patients without active TB were randomized to receive either ethambutol 800 mg and isoniazid 300 mg daily for six-months (6EH) or isoniazid 300 mg daily for 36-months (36H). Drugs were dispensed fortnightly and adherence checked by home visits. Patients had chest radiograph, sputum smear and culture performed every six months, in addition to investigations if they developed symptoms. The primary endpoint was incident TB while secondary endpoints were all-cause mortality and adverse events. Survival analysis was performed on the modified intent to treat population (m-ITT) and rates compared.

Findings

Tuberculosis developed in 22 (6.4%) of 344 subjects in the 6EH arm and 13 (3.8%) of 339 subjects in the 36H arm with incidence rates of 2.4/100py (95%CI- 1.4–3.5) and 1.6/100py (95% CI-0.8–3.0) with an adjusted rate ratio (aIRR) of 1.6 (0.8–3.2). Among TST-positive subjects, the aIRR of 6EH was 1.7 (0.6–4.3) compared to 36H, p = 0.8. All-cause mortality and toxicity were similar in the two arms. Among 15 patients with confirmed TB, 4 isolates were resistant to isoniazid and 2 were multidrug-resistant.

Interpretation

Both regimens were similarly effective in preventing TB, when compared to historical incidence rates. However, there was a trend to lower TB incidence with 36H. There was no increase in isoniazid resistance compared to the expected rate in HIV-infected patients.

The trial is registered at ClinicalTrials.gov, NCT00351702.

Treatment of latent tuberculosis infection in HIV: shorter or longer?

Nine months of daily isoniazid is efficacious in treating latent M. tuberculosis infection, but completion rates are low, limiting treatment effectiveness. In 2011, three important studies were published involving novel regimens for the treatment of latent M. tuberculosis infection. At least 36 months of isoniazid was more effective than 6 months of isoniazid in one study, but not in another-both of which were conducted among tuberculin skin test positive HIV-infected adults living in high tuberculosis incidence settings. Three months of once-weekly isoniazid plus rifapentine or twice-weekly isoniazid plus rifampin (both given under direct observation) resulted in tuberculosis rates similar to those seen with 6 months of isoniazid among HIV-infected persons in high tuberculosis incidence settings. Three months of once-weekly, directly-observed isoniazid plus rifapentine was at least as effective as 9 months of daily isoniazid among predominantly HIV-uninfected persons living in low and medium tuberculosis incidence countries. The 3-month once-weekly isoniazid plus rifapentine regimen demonstrates promise for treatment of latent M. tuberculosis infection in HIV-infected persons.

Feasibility and efficacy of isoniazid prophylaxis for latent tuberculosis in HIV-infected clients patients in Thailand

A prospective study was conducted in 4339 HIV-positive clients at the Thai Red Cross AIDS Research Centre (TRC-ARC) Anonymous clinic, Bangkok, Thailand between January 2003 and April 2008. A tuberculin skin test (TST) was done for all patients without a previous history of tuberculosis (TB). Nine months of isoniazid (INH) was given for all positive TST/no active TB. TST-negative clients were asked to repeat the TST annually. The study aim was to evaluate the feasibility and efficacy of INH prophylaxis for preventing TB in HIV-positive Thai patients. Of those patients, 4111 (94.7%) had a TST done; 1157 (28.1%) were TST positive and 799 patients started INH prophylaxis. In all, 551 (69%) and 633 (79.2%) patients completed 9 months and 6 months of INH, respectively; 176 (20.2%) patients had a negative TST at baseline and subsequently converted to positive. Only patients with a baseline CD4 >200 cells/μL (p=0.000) and currently on antiretroviral (ARV) treatment (p=0.000) were related to having a positive TST. This baseline CD4 level was also significantly related to higher INH completion rates at 6 months (p=0.000). Interestingly, none of INH completion patients developed active TB. The feasibility of INH prophylaxis in TST-positive patients in this setting is possible. However, the long-term advantage of INH prophylaxis in terms of TB prevention, especially in HIV-1-infected patients on highly active antiretroviral therapy (HAART), is still an issue that needs more research.

Diagnosing latent tuberculosis in high-risk individuals: rising to the challenge in high-burden areas

A key challenge to greater progress in tuberculosis (TB) control is the reservoir of latent TB infection (LTBI), which represents a huge long-lived reservoir of potential TB disease. In parts of Africa, as many as 50% of 15-year-olds and 77%-89% of adults have evidence of LTBI. A second key challenge to TB control is the human immunodeficiency virus (HIV)-associated TB epidemic, and Africa alone accounts for one-quarter of the global burden of HIV-associated TB. HIV co-infection promotes both reactivation TB from LTBI and rapidly progressive primary TB following recent exposure to Mycobacterium tuberculosis. Preventing active TB and tackling latent infection in addition to the Directly Observed Treatment, Short-Course (DOTS) strategy could improve TB control in high-burden settings, especially where there is a high prevalence of HIV co-infection. Current strategies include intensified case finding (ICF), TB infection control, antiretroviral therapy (ART), and isoniazid preventive therapy (IPT). Although ART has been widely rolled out, ICF and IPT have not. A key factor limiting the rollout and effectiveness of IPT and ICF is the limitations of existing tools to both diagnose LTBI and identify those persons most at risk of progressing to active TB. In this review, we examine the obstacles and consider current progress toward the development of new tools to address this pressing global problem.