Comparing QuantiFERON-tuberculosis gold, T-SPOT tuberculosis and tuberculin skin test in HIV-infected individuals from a low prevalence tuberculosis country

Resistance to tuberculin skin test/interferon-gamma release assay conversion among highly TB exposed, HIV infected goldminers in South Africa

BACKGROUND

A small proportion of goldminers in South Africa resist tuberculin skin test (TST)/interferon-gamma release assay (IGRA) conversion despite high rates of HIV and prolonged exposure to TB. We conducted a study among HIV-infected goldminers to determine the: i) proportion who resisted TST/IGRA conversion and ii) epidemiological factors associated with resistance to TST/IGRA conversion.

METHODS

We enrolled HIV-infected goldminers who were on antiretroviral treatment, aged 33-60 years, with ≥15 years' service, no prior or current TB, no silicosis, and with body mass index >18.5 kg/m2. TST/IGRA conversion was assessed at baseline, 6 months, and 12 months using TST and QuantiFERON-TB-Gold-Plus (QFT-Plus). Miners were considered resisters if they had a zero TST response and a negative QFT-Plus at all visits. Logistic regression was used to identify epidemiological factors associated with TST/IGRA conversion resistance.

RESULTS

We enrolled 245 HIV-infected miners with median age of 48 years (interquartile-range [IQR]: 44-52 years) and median CD4 count, 506 cells/ µ L (IQR: 372-677 cells/ µ L). Overall, 98.4% (241) were males and 99.2% (243) were Black/African with a median time of 24 years (IQR: 18-29 years) in the workforce. Of those completing all follow-ups, 24.3% (50/206) resisted TST/IGRA conversion. Miners who had a history of taking isoniazid preventive therapy (IPT) (adjusted odds ratio (aOR) 2.34; 95% confidence interval (CI): 1.14-4.80; p = 0.020) were more likely to resist TST/IGRA conversion. However, those from Mozambique (aOR 0.16; 95% CI: 0.04-0.71; p = 0.016) and those who had a CD4 count ≥500 cells/ µ L (aOR 0.46; 95% CI: 0.23-0.92; p = 0.028) were less likely to resist TST/IGRA conversion.

CONCLUSION

Similar to previous longitudinal cohort studies, we found a small proportion of HIV-infected goldminers who resisted TST/IGRA conversion. This was positively associated with prior IPT, but negatively associated with lower CD4 count and being from Mozambique. However, mechanisms underlying TST/IGRA conversion resistance are not well understood.

Advances in understanding immune homeostasis in latent tuberculosis infection

Nearly one-fourth of the global population is infected by Mycobacterium tuberculosis (Mtb), and approximately 90%-95% remain asymptomatic as latent tuberculosis infection (LTBI), an estimated 5%-10% of those with latent infections will eventually progress to active tuberculosis (ATB). Although it is widely accepted that LTBI transitioning to ATB results from a disruption of host immune balance and a weakening of protective immune responses, the exact underlying immunological mechanisms that promote this conversion are not well characterized. Thus, it is difficult to accurately predict tuberculosis (TB) progression in advance, leaving the LTBI population as a significant threat to TB prevention and control. This article systematically explores three aspects related to the immunoregulatory mechanisms and translational research about LTBI: (1) the distinct immunocytological characteristics of LTBI and ATB, (2) LTBI diagnostic markers discovery related to host anti-TB immunity and metabolic pathways, and (3) vaccine development focus on LTBI. This article is categorized under: Infectious Diseases > Molecular and Cellular Physiology Infectious Diseases > Genetics/Genomics/Epigenetics Immune System Diseases > Genetics/Genomics/Epigenetics.

Screening for tuberculosis infection and effectiveness of preventive treatment among people with HIV in low-incidence settings

OBJECTIVE

To determine the yield of screening for latent tuberculosis infection (LTBI) among people with HIV (PWH) in low tuberculosis (TB) incidence countries (<10 TB cases per 100 000 persons).

DESIGN

A systematic review and meta-analysis were performed to assess prevalence and predictive factors of LTBI, rate of TB progression, effect of TB preventive treatment (TPT), and numbers needed to screen (NNS).

METHODS

PubMed and Cochrane Library were searched for studies reporting primary data, excluding studies on active or paediatric TB. We extracted LTBI cases, odds ratios, and TB incidences; pooled estimates using a random-effects model; and used the Newcastle-Ottawa scale for bias.

RESULTS

In 51 studies with 65 930 PWH, 12% [95% confidence interval (CI) 10-14] had a positive LTBI test, which was strongly associated with origin from a TB-endemic country [odds ratio (OR) 4.7] and exposure to TB (OR 2.9). Without TPT (10 629 PWH), TB incidence was 28/1000 person-years (PY; 95% CI 12-45) for LTBI-test positive versus 4/1000 PY (95% CI 0-7) for LTBI-test-negative individuals. Among 625 PWH (1644 PY) receiving TPT, 15 developed TB (6/1000 PY). An estimated 20 LTBI-positive individuals would need TPT to prevent one case of TB, and numbers NNS to detect LTBI or prevent active TB varied according to a-priori risk of LTBI.

CONCLUSION

The relatively high prevalence of LTBI among PWH and the strong correlation with origin from a TB-endemic country support risk-stratified LTBI screening strategies for PWH in low-incidence countries and treating those who test positive.

Positive rate and risk factors of latent tuberculosis infection among persons living with HIV in Jiangsu Province, China

Objective

To analyze the latent tuberculosis infection (LTBI) among persons living with HIV(PLWH) in Jiangsu Province, to explore the factors affecting the positive rate of LTBI, and to take appropriate measures to control tuberculosis (TB) infection.

Methods

A cross-sectional study was conducted among PLWH in Jiangsu Province from June to July 2021. All PLWH in Jiangsu Province were used as the study population. Currently, the diagnosis of LTBI lacks a "gold standard" and can only be assisted by the immunological method. In this study, Tuberculin skin test (TST), ESAT6-CFP10 test (EC), and QuantiFERON-TB gold in-tube (QFT) were used to detect the positive rate of LTBI among PLWH and to analyze their risk factors.

Results

A total of 340 prisoners were included, 89.7% were male, the median age was 38 years [Interquartile Range (IQR):32-46 years], these patients were on Antiviral Therapy (ART), and median CD4 counts was 376 (IQR: 261-496), 103 (30.3%) were positive in at least one test, LTBI by TST was 16.5%, LTBI by EC was 15.9%, LTBI by QFT was 26.2%. Univariate analysis showed the results for TST, EC, and QFT were not affected by CD4 counts (p>0.05), and multivariate analysis showed that a history of incarceration was associated with an increased risk of positive TST (adjusted odds ratio [aOR]=1.98;95% CI,1.03-3.82), EC (aOR=2.65;95% CI,1.37-5.12) and QFT (aOR=2.01;95%CI,1.12-3.57), in addition, female gender was associated with increased risk of positive TST (aOR=3.66;95%CI,1.60-8.37) and EC (aOR=3.43;95%CI,1.46-8.07), and contact history of TB patients was associated with increased risk of TST (aOR= 2.54;95%CI,1.23-5.22) and QFT (aOR=2.03;95%CI,1.03-3.99), and ethnic minorities (aOR=0.26;95%CI,0.12-0.57), longer duration of incarceration was associated with an increased risk of positive QFT (aOR=1.12;95%CI,1.02-1.24). Conclusions Female gender, and ethnic minorities, history of incarceration, longer duration of incarceration, and contact history of TB patients are risk factors for LTBI among PLWH in Jiangsu Province, and attention should be paid to TB control in this population.

Factors Influencing False-Negative Results of QuantiFERON-TB Gold In-Tube (QFT-GIT) in Active Tuberculosis and the Desirability of Resetting Cutoffs for Different Populations: A Retrospective Study

Objectives The value of QuantiFERON-TB Gold In-Tube (QFT-GIT) in the diagnosis of TB varies by population, comorbidities, and other factors. In this study, we aimed to investigate factors that influence false-negative results of QFT-GIT test in the diagnosis of TB as well as the impact of different cutoffs on the diagnostic value. Methods A total of 3562 patients who underwent QFT-GIT tests at Shanghai Pulmonary Hospital were enrolled retrospectively between May 2016 and May 2017. False-negative and false-positive results were analyzed using different clinical stratifications. The optimal cutoff values were established under different clinical conditions. Results Positive QFT-GIT results greatly shortened the time taken to diagnose smear-negative TB. The factors of age, smear and culture results, site of TB, comorbidity with tumors, white blood cell count, neutrophil count, and CD4/CD8 ratio were significantly correlated with false-negative QFT-GIT results (p < 0.05). Personalized cutoff values were established according to different influencing factors. The results showed high consistency between the smear-negative and total populations. Conclusion QFT-GIT can facilitate the early diagnosis of smear-negative TB. The diagnostic performance of the QFT-GIT test in the diagnosis of active TB was shown to be affected by many clinical factors. Personalized cutoff values may have superior value in the identification of active tuberculosis under different conditions.

Increased Expression of IL-10 in Peripheral Blood Mononuclear Cells Correlates with Negative Interferon-γ Release Assay Results in Culture-Confirmed Tuberculosis Patients

Introduction

Interferon-γ release assays (IGRAs) can have high false-negative rates for active tuberculosis (TB) cases. Here we investigated factors, including potential anti-inflammatory mechanisms, that contributed to false-negative IGRA results.

Methods

We established two cohorts. In the first cohort, we reviewed IGRA results for confirmed TB cases diagnosed in our hospital in 2018. Cases with false-negative IGRA results were analysed to identify factors contributing to false-negative results. In the second cohort, we prospectively studied IL-10 expression levels in peripheral blood mononuclear cells (PBMCs) of IGRAs-positive and IGRAs-negative TB cases after antigenic stimulation to correlate IL-10 expression with IGRAs results.

Results

Of 1232 culture-confirmed TB cases, 1124 produced true-positive IGRA results and 108 had false-negative IGRA results. Multivariate logistic regression analysis identified glucocorticoid use and extrapulmonary TB as independent risk factors for false-negative IGRA results. Notably, IL-10 expression of the IGRA-negative group was significantly up-regulated as compared to that of the IGRA-positive group. The average cell supernatant IL-10 concentration of the IGRA-negative group was 4.77 pg/mL, a value that was statistically greater than the IGRA-positive group concentration (1.47 pg/mL, P = 0.007). After PBMCs pretreatment with BRD6989 (to enhance IL-10 secretion), average IFN-γ concentrations in cell supernatants from the IGRA-positive group significantly decreased from 59.73 pg/mL to 33.79 pg/mL (P = 0.011). By contrast, addition of AS101 (to inhibit IL-10 secretion) to false-negative group PBMCs led to an increase of average IFN-γ concentration in cell supernatants from 19.01 pg/mL to 45.10 pg/mL (P = 0.030), a result that was inversely correlated with IL-10 concentration.

Conclusion

Our data demonstrate that increased IL-10 secretion by PBMCs is inversely correlated with IGRA assay results in culture-confirmed TB patients. Glucocorticoids use and extrapulmonary TB are significantly associated with false-negative IGRA results. Combination testing to measure IL-10 secretion and IFN-γ release is recommended to improve IGRAs specificity.

Novel health system strategies for tuberculin skin testing at primary care clinics: Performance assessment and health economic evaluation

Background

Tuberculin skin test (TST) for guiding initiation of tuberculosis preventive therapy poses major challenges in high tuberculosis burden settings.

Methods

At a primary care clinic in Johannesburg, South Africa, 278 HIV-positive adults self-read their TST by reporting if they felt a bump (any induration) at the TST placement site. TST reading (in mm) was fast-tracked to reduce patient wait time and task-shifted to delegate tasks to lower cadre healthcare workers, and result was compared to TST reading by high cadre research staff. TST reading and placement cost to the health system and patients were estimated. Simulations of health system costs were performed for 5 countries (USA, Germany, Brazil, India, Russia) to evaluate generalizability.

Results

Almost all participants (269 of 278, 97%) correctly self-identified the presence or absence of any induration [sensitivity 89% (95% CI 80,95) and specificity 99.5% (95% CI 97,100)]. For detection of a positive TST (induration ≥ 5mm), sensitivity was 90% (95% CI 81,96) and specificity 99% (95% CI 97,100). TST reading agreement between low and high cadre staff was high (kappa 0.97, 95% CI 0.94, 1.00). Total TST cost was 2066 I$ (95% UI 594, 5243) per 100 patients, 87% (95% UI 53, 95) of which were patient costs. Combining fast-track and task-shifting, reduced total costs to 1736 I$ (95% UI 497, 4300) per 100 patients, with 31% (95% UI 15, 42) saving in health system costs. Combining fast-tracking, task-shifting and self-reading, lowered the TST health system costs from 16% (95% UI 8, 26) in Russia to 40% (95% UI 18, 54) in the USA.

Conclusion

A TST strategy where only patients with any self-read induration are asked to return for fast-tracked TST reading by lower cadre healthcare workers is a promising strategy that could be effective and cost-saving, but real-life cost-effectiveness should be further examined.

Prevalence of positive IGRAs and innate immune system in HIV-infected individuals in Japan

INTRODUCTION

Human immunodeficiency virus (HIV) infected individuals are at increased risk of developing active tuberculosis (TB). TB incidence remains higher than in non-HIV subjects after antiretroviral therapy (ART) initiation. This study was conducted to estimate the prevalence of positive IGRA, reflecting latent tuberculosis infection and/or a history of active TB, in HIV-infected individuals after ART initiation in Japan.

METHODS

Two IGRAs (Interferon (IFN)-γ release assays), QuantiFERON®-TB Gold Plus (QFT-Plus) and T-Spot®.TB (TSPOT), were used. We also analyzed the TB associated risk factors for the IGRAs results and the role of CD4⁺ T-cells, CD8⁺ T-cells and NK cells for producing IFN-γ. We also analyzed the risk factors for positive IGRA responses and the role of CD4⁺ T-cells, CD8⁺ T-cells and NK cells for producing IFN-γ.

RESULTS

One hundred eight-four subjects were prospectively enrolled. Median age was 49 years. The positivity rates of QFT-Plus and TSPOT were 7.6% [95%CI 4.6-12.4] and 2.7% [95%CI 1.2-6.2], respectively, with significant difference. TB-associated risk factors and NK cells ≥300/μL were selected as independently significant factors by multivariate logistic regression. The NK cell count revealed significant linear regression with IFN-γ production responding to TB-specific antigens.

CONCLUSIONS

The prevalence of positive IGRAs was 2.7%-7.6%. QFT-Plus would be practical for a higher positivity rate and reflect TB risk factors. The innate immune system, referring to IFN-γ production, plays an important role in the immune response to TB-specific antigens even after initiating ART.

Effects of Pregnancy and Isoniazid Preventive Therapy on M. tuberculosis Interferon Gamma Response Assays in Women with HIV

BACKGROUND

Pregnancy is accompanied by immune suppression. We hypothesized that M. tuberculosis-specific inflammatory responses used to identify latent tuberculosis infection (LTBI) lose positivity during pregnancy. We also hypothesized that isoniazid preventive therapy (IPT) may revert LTBI diagnoses because of its sterilizing activity.

METHODS

944 women with HIV participating in a randomized, double-blind, placebo-controlled study comparing 28 weeks of IPT antepartum versus postpartum, were tested by QuantiFERON-gold-in-tube (QGIT) antepartum and by QGIT and tuberculin skin test (TST) at delivery and postpartum. Serial QGIT positivity was assessed by logistic regression using generalized estimating equations.

RESULTS

From entry to delivery, 68 (24%) of 284 QGIT-positive women (24%) reverted to QGIT-negative or indeterminate. Of these, 42 (62%) recovered QGIT positivity postpartum. The loss of QGIT positivity during pregnancy was explained by decreased IFNγ production in response to TB antigen and/or mitogen. At delivery, QGIT identified 205 and TST 113 women with LTBI. Corresponding numbers postpartum were 229 and 122 women. QGIT and TST kappa agreement coefficients were 0.4 and 0.5, respectively. Among QGIT-positive women antepartum or at delivery, 34 (12%) reverted to QGIT-negative after IPT. There were no differences between women who initiated IPT antepartum or postpartum.

CONCLUSIONS

Decreased IFNγ responses in pregnancy reduced QGIT positivity, suggesting that this test cannot reliably rule out LTBI during pregnancy. TST was less affected by pregnancy, but had lower positivity compared to QGIT at all time points. IPT was associated with loss of QGIT positivity, the potential clinical consequences of which need to be investigated.

Good Agreement between an Interferon Gamma Release Assay and Tuberculin Skin Tests in Testing for Latent Tuberculosis Infection among HIV-Infected Patients in Indonesia

BACKGROUND

Latent tuberculosis infection is a condition where there is a persistent immune response to Mycobacterium tuberculosis without clinical manifestations of tuberculosis. Currently, there is no gold standard to diagnose latent tuberculosis infection. The tuberculin skin test and interferon-gamma release assay are currently used to diagnose latent tuberculosis infection. However, studies have shown inconsistencies regarding the level of agreement between these tests in different settings. In this study, we aimed to evaluate the agreement between these two tests for diagnosing latent tuberculosis infection in human immunodeficiency virus (HIV)-infected individuals.

METHODS

We screened HIV patients with no clinical symptoms of tuberculosis, a normal chest X-ray, and no history of tuberculosis or use of antituberculous drugs. Participants were tested with tuberculin skin test (TST) and T-SPOT.TB (an interferon gamma release assay) simultaneously. Participants' HIV stage was determined by measuring the level of CD4+ T-lymphocytes. Tuberculosis status was confirmed by sputum examination using GeneXpert. The level of agreement between the TST and T-SPOT.TB results was measured using Cohen's κ coefficient.

RESULTS

Of the 112 participants, 20 had a positive T-SPOT.TB test result, and 21 had a positive TST result. The TST and T-SPOT.TB test results showed a high level of agreement (κ = 0.648, P < 0.001). Performance of the tests did not vary with CD4+ level. However, in participants with CD4+ < 200 cells/mm³, T-SPOT.TB detected more latent tuberculosis infections than the TST.

CONCLUSION

There was good agreement between the TST and T-SPOT.TB results of latent tuberculosis infection in participants. TST is the preferred test for diagnosing latent tuberculosis infection in HIV-infected patients, especially in resource-limited settings, because it is simple and cost-effective. However, T-SPOT.TB may be useful to rule out latent tuberculosis infection in patients with severe immunodeficiency.

Comparison of Three Cellular Immunoassays to Detect Tuberculosis Infection in 876 Healthy Recruits

The currently purified protein derivative (PPD) skin test and 2 interferon (IFN)-γ release assays (IGRAs) were usually used to detect Mycobacterium tuberculosis infection. We try to evaluate the performance of these methods to detect latent tuberculosis infection (LTBI) in this study. Each subject of the 876 recruits (19.05 ± 1.55, 17-24) underwent the PPD test, enzyme-linked immunospot (ELISPOT) assay, and chemiluminescent enzyme immunoassay (CLEIA). The prevalence of LTBI among the participants, as estimated by PPD, ELISPOT, and CLEIA, was 49.89% (437/876), 25.34% (222/876), and 28.77% (252/876), respectively. Of the participants, positive results were noted in 12.79% (112/876) for both ELISPOT and PPD, 19.52% (171/876) for both CLEIA and PPD; 9.82% (86/876) for 2 IGRAs; and 6.62% (58/876) for all 3 methods. Overall, the consistency among the 3 tests was 36.99% (324/876). ELISPOT-positive rate (41.38%) in the recruits with a PPD result ≥20 mm was higher than PPD <20 mm (24.76%; P < 0.05). Increased PPD skin reactions were associated with significantly increased CLEIA-positive rates and IFN-γ levels. Of 307 recruits without the bacillus Calmette-Guérin (BCG) vaccination, 2 IGRA (42.19%)-positive rates in the PPD-positive group were significantly higher than those in the PPD-negative group (28.40% and 23.05%; P < 0.05 and P < 0.01, respectively).There was low correlation and poor consistency among 2 IGRAs and PPD in healthy recruits, but IGRAs may be more accurate screening methods for TB infection in the countries with BCG vaccination.

Comparison of Interferon-γ Release Assays and the Tuberculin Skin Test for Diagnosis of Tuberculosis in Human Immunodeficiency Virus: A Systematic Review

Background

It remains uncertain if interferon-γ release assays (IGRAs) are superior to the tuberculin skin test (TST) for the diagnosis of active tuberculosis (TB) or latent tuberculosis infection (LTBI) in immunosuppressed populations including people with human immunodeficiency virus (HIV) infection. The purpose of this study was to systematically review the performance of IGRAs and the TST in people with HIV with active TB or LTBI in low and high prevalence TB countries.

Methods

We searched the MEDLINE database from 1966 through to January 2017 for studies that compared results of the TST with either the commercial QuantiFERON-TB Gold in Tube (QFTGT) assay or previous assay versions, the T-SPOT.TB assay or in-house IGRAs. Data were summarized by TB prevalence. Tests for concordance and differences in proportions were undertaken as appropriate. The variation in study methodology was appraised.

Results

Thirty-two studies including 4,856 HIV subjects met the search criteria. Fourteen studies compared the tests in subjects with LTBI in low TB prevalence settings. The QFTGT had a similar rate of reactivity to the TST, although the first-generation version of that assay was reactive more commonly. IGRAs were more frequently positive than the TST in HIV infected subjects with active TB. There was considerable study methodology and population heterogeneity, and generally low concordance between tests. Both the TST and IGRAs were affected by CD4 T-cell immunodeficiency.

Conclusion

Our review of comparative data does not provide robust evidence to support the assertion that the IGRAs are superior to the TST when used in HIV infected subjects to diagnose either active TB or LTBI.

Cost analysis of tuberculin skin test and the QuantiFERON-TB Gold In-tube test for tuberculosis screening in a correctional setting in Dallas, Texas, USA

BACKGROUND

Tuberculosis (TB) disproportionately affects immigrants, HIV-infected individuals, and those living in crowded settings such as homeless shelters and correctional facilities. Although the majority of jails and prisons use a tuberculin skin test (TST) for latent tuberculosis infection (LTBI) screening, limited data exist on the clinical performance and costs of the TST compared to interferon gamma release assays (IGRAs) in this setting.

METHODS

A prospective pilot study comparing cost between TST and an IGRA (QuantiFERON Gold In-tube, QFT-GIT) for the detection of LTBI in a convenience sample of inmates entering the Dallas County Jail (DCJ) was conducted June-October 2014. Participants completed a risk questionnaire, TST placement, QFT-GIT testing, and were offered opt-out HIV-Ab testing. LTBI prevalence based on TST and QFT-GIT results, an evaluation of discordant results and a cost analysis are presented.

RESULTS

A total of 529 subjects were enrolled. The majority were male (75 %), and 46 % were Black, 29 % White, and 24 % Hispanic. Most (85 %) had been previously incarcerated. Over 28 % of participants were released prior to TST reading, with paired QFT-GIT and TST results available for 351 subjects. Of these, nine (2.6 %) tested positive by TST and 47 (13.4 %) tested positive by QFT-GIT. It costs $23.27 more per inmate per year to screen with QFT-GIT than TST in this population, though the cost per LTBI case detected was nearly three times higher for TST than QFT-GIT ($1247 v $460).

CONCLUSIONS

We found a substantially higher rate of QFT-GIT positivity compared to TST in this sample of individuals entering the Dallas County Jail. Although no gold standard exists, this finding may indicate under-recognized LTBI in this setting. QFT-GIT as an initial screening tool was more time-efficient, had four-fold fewer labor costs and provided results on more individuals when compared with the TST. The overall cost of QFT-GIT was $23.27 more per inmate per year, though the cost per LTBI case detected was nearly three times higher for TST than QFT-GIT. Further research is needed to determine the long-term performance of IGRA testing in the correctional setting and the public health implications of pairing QFT-GIT screening with other tests for communicable diseases.

The Clinical Usefulness of Tuberculin Skin Test versus Interferon-Gamma Release Assays for Diagnosis of Latent Tuberculosis in HIV Patients: A Meta-Analysis

BACKGROUND

Accurate diagnosis of latent tuberculosis infection (LTBI) is becoming increasingly concerning due to the increasing the HIV epidemic, which have increased the risk for reactivation to active tuberculosis (TB) infection. LTBI is diagnosed by tuberculin skin test (TST) and interferon-gamma release assays (IGRAs).

OBJECTIVES

The aim of the present study was to conduct a meta-analysis of published papers on the agreement (kappa) between TST and QuantiFERON-TB Gold In-Tube (QFT-GIT) tests for diagnosis of LTBI in HIV patient.

METHODS

Electronic databases including PubMed/Medline, Elsevier/Scopus and Embase/Ovid were reviewed up Jan. 2016. We performed a random effect model meta-analysis for estimation of pooled Kappa between the two methods of diagnosis. Meta regression was used for assessing potential heterogeneity and Egger's test was used for assessing small study effect and publication bias.

RESULTS

The initial search strategy produced 6744 records. Of them, 23 cross-sectional studies met the inclusion criteria and 20 studies entered in meta-analysis. The pooled kappa was and prevalence-adjusted and bias-adjusted kappa (PABAK) were 0.37 (95% CI: 0.28, 0.46) and 0.59 (0.49, 0.69). The discordance of TST-/QFT-GIT+ was more than TST+/QFT-GIT-. Kappa estimate between two tests was linearly associated with age and prevalence index and inversely associated with bias index.

CONCLUSION

Fair agreement between TST and QFT-GIT makes it difficult to know whether TST is as useful as the QFT-GIT in HIV-infected patients. The higher discordance of TST-/QFT-GIT+ in compared to TST+/QFT-GIT- can induce the higher sensitivity of QFT-GIT for diagnosis LTBI in HIV patients. Disagreement between two tests can be influenced by error in measurements and prevalence of HIV.

Utility of QuantiFERON-TB Gold In-Tube Test in the Diagnosis of Latent TB in HIV-Positive Patients in a Medium-TB Burden Country

BACKGROUND

The authors aimed to compare TST with QuantiFERON-TB Gold In-Tube (QFT) for detecting latent tuberculosis infection (LTBI) in HIV-infected patients in Iran as a TB-medium endemic country.

METHODS

In a cross-sectional design,130 HIV-positive patients in HIV clinic of Tehran University were studied. Patients screened for LTBI with QFT and TST simultaneously. Concordance between 2 tests results and variables associated with tests discordance were assessed.

RESULTS

Positive results found in 24.6% for TST and 7.7% for QFT. Overall agreement between them was 73.85% (Kappa = 0.083). History of imprisonment was associated with more positive TST (P = 0.014) and QFT (P = 0.01). Patients with intravenous drug use (IDU) history had significant discordant results (0.018).

CONCLUSION

The authors recommend QFT for all negative cases of TST in HIV-positive patients especially who had history of IDU.

A Clinical Algorithm to Identify HIV Patients at High Risk for Incident Active Tuberculosis: A Prospective 5-Year Cohort Study

Background

Predicting the risk of tuberculosis (TB) in people living with HIV (PLHIV) using a single test is currently not possible. We aimed to develop and validate a clinical algorithm, using baseline CD4 cell counts, HIV viral load (pVL), and interferon-gamma release assay (IGRA), to identify PLHIV who are at high risk for incident active TB in low-to-moderate TB burden settings where highly active antiretroviral therapy (HAART) is routinely provided.

Materials and Methods

A prospective, 5-year, cohort study of adult PLHIV was conducted from 2006 to 2012 in two hospitals in Taiwan. HAART was initiated based on contemporary guidelines (CD4 count < = 350/μL). Cox regression was used to identify the predictors of active TB and to construct the algorithm. The validation cohorts included 1455 HIV-infected individuals from previous published studies. Area under the receiver operating characteristic (ROC) curve was calculated.

Results

Seventeen of 772 participants developed active TB during a median follow-up period of 5.21 years. Baseline CD4 < 350/μL or pVL ≥ 100,000/mL was a predictor of active TB (adjusted HR 4.87, 95% CI 1.49–15.90, P = 0.009). A positive baseline IGRA predicted TB in patients with baseline CD4 ≥ 350/μL and pVL < 100,000/mL (adjusted HR 6.09, 95% CI 1.52–24.40, P = 0.01). Compared with an IGRA-alone strategy, the algorithm improved the sensitivity from 37.5% to 76.5%, the negative predictive value from 98.5% to 99.2%. Compared with an untargeted strategy, the algorithm spared 468 (60.6%) from unnecessary TB preventive treatment. Area under the ROC curve was 0.692 (95% CI: 0.587–0.798) for the study cohort and 0.792 (95% CI: 0.776–0.808) and 0.766 in the 2 validation cohorts.

Conclusions

A validated algorithm incorporating the baseline CD4 cell count, HIV viral load, and IGRA status can be used to guide targeted TB preventive treatment in PLHIV in low-to-moderate TB burden settings where HAART is routinely provided to all PLHIV. The implementation of this algorithm will avoid unnecessary exposure of low-risk patients to drug toxicity and simultaneously, reduce the burden of universal treatment on the healthcare system.

Decreasing cost effectiveness of testing for latent TB in HIV in a low TB incidence area

Testing for latent tuberculosis infection (LTBI) in HIV-infected persons in low tuberculosis (TB) incidence areas is often recommended. Using contemporary, clinical data, we report the yield and cost-effectiveness of testing all HIV attendees, two current UK strategies and no LTBI testing. Economic modelling was performed utilising 10-year follow up data from a large HIV clinical cohort. Outcomes were numbers of cases of active TB and incremental cost per quality-adjusted life year (QALY) gained. Between 2000 and 2010, 256 people were treated for TB/HIV co-infection. 72 (28%) occurred ≥3 months after HIV diagnosis and may have been prevented by LTBI testing. Between 2000 and 2005, the incremental cost per QALY gained for the British HIV Association (BHIVA) and UK National Institute of Care Excellence (NICE) strategies, and testing all clinic attendees was €6270, €6998 and €33,473, respectively. These rose to €9332, €32,564 and €74,067, respectively, between 2005 and 2010. Probabilistic sensitivity analysis suggested that at a threshold of €24,000 per additional QALY, the most cost-effective strategies would be NICE or testing all in 2000-2005 and BHIVA during 2005-2010. Both UK testing regimens missed cases but are cost-effective compared with no testing. Using recent data, they all became more expensive, suggesting that alternative or more targeted TB testing strategies must be considered.

Comparison of an interferon-gamma release assay and the tuberculin skin test for diagnosis of latent tuberculosis in homeless people in Iran: a cross-sectional study

BACKGROUND

The aim of this study was to evaluate of the concordance between the results of the tuberculin skin test (TST) and an interferon-γ release assay (QuantiFERON test, QFT-GIT) for diagnosis of latent tuberculosis infection (LTBI) in homeless people in Tehran city, Iran.

METHODS

This cross-sectional study was conducted from June to August 2012. Homeless people were eligible to participate in the study if they were 18-60 years old.

RESULTS

Among 569 homeless people, 46.22% (95% confidence interval (CI) = 42.16-50.33%) and 20.39% (95% CI = 17.28-23.9%) were QFT-GIT and TST positive, respectively. Among these participants, the prevalence of LTBI with positivity of at least one of the tests was 52.2%. The overall agreement between QFT-GIT and TST was 62.21% (kappa = 0.21, 95% CI = 0.13-0.29, p < 0.001). Factors associated with positive results in QFT-GIT and TST were older age, being male, having a longer history of homelessness and having a history of incarceration in the last 10 years.

CONCLUSIONS

A high prevalence of LTBI was seen among homeless people in this study. There was a poor concordance between QFT-GIT and TST among this group. To better assess the utility of QFT-GIT in detection of LTBI further studies with a low prevalence of LTBI in this group are recommended.

Relationship between T-SPOT.TB responses and numbers of circulating CD4+ T-cells in HIV infected patients with active tuberculosis

This study sought to evaluate the performance of the T-SPOT.TB assay for the diagnosis of active tuberculosis (TB) in human immunodeficiency virus (HIV) infected patients. One hundred confirmed HIV-infected patients with active TB and known T-SPOT.TB and CD4+ T-cell counts were enrolled in this clinical retrospective study. We found that patients with lower CD4+ T-cell counts (11-50 cells/μL) had the lowest T-SPOT.TB positive rates (50%), and patients with higher CD4+ T-cell counts (50-100 cells/μL) had the highest T-SPOT.TB positive rates (75%). However, there were no significant differences between the T-SPOT.TB positive rates of patients with different CD4+ T-cell counts (< 10, 11-50, 51-100 and > 100 cells/μL) (χ(2) = 3.7747, p = 0.287). The patients with positive TB culture results had significantly higher T-SPOT.TB positive rates (78.9%) than patients that were culture-negative (44.3%) (χ(2) = 12.8303, p < 0.001). Other variables, including gender, age, TB disease classification, HIV RNA level, and highly reactive antiretroviral therapy (HAART), had no significant effects on T-SPOT.TB positive rates. The number of spot-forming cells (SFCs) reactive with ESAT-6, CFP-10 and ESAT-6/CFP-10-specific T cells detected by T-SPOT.TB were positively is strongly related to the degree of immunodeficiency, while the T-SPOT.TB positive rates are less dependent on the level of CD4+ T-cell depletion in HIV infection and active TB.

Tuberculin skin test and QuantiFERON-TB Gold In-tube Test for latent tuberculosis in Thai HIV-infected adults

BACKGROUND AND OBJECTIVE

Limited data exist for the performance of QuantiFERON-TB Gold In-tube Test (QFT-IT) in comparison to tuberculin skin test (TST) for detecting latent tuberculosis (LTB) in patients with human immunodeficiency virus (HIV) infection from tuberculosis (TB)-endemic Asia-Pacific countries.

METHODS

A cohort study of Thai HIV-infected patients without history of TB or LTB treatment was conducted from March 2012 through March 2013. Each patient underwent simultaneous TST and QFT-IT.

RESULTS

Among the 150 enrolled subjects, the median age was 40 years (range 17-65), 53% were male, and the median CD4 count was 367 cells/μL (range 8-1290). Reactive TST and positive QFT-IT were 16% and 13%, respectively, with low concordance between tests (kappa = 0.26); correlation between TST reaction size and level of interferon-γ was moderate (r = 0.34). Independent factors associated with discordant results were long-term smoking (adjusted odds ratio (aOR) 5.74; P = 0.002) for TST-reactive, QFT-IT-negative subjects, and age greater than 52 years (aOR 5.56; P = 0.02) and female gender (aOR 4.40; P = 0.04) for TST non-reactive, QFT-IT-positive subjects. The level of agreement between both tests improved when using a TST cut-off of ≥ 10 mm (kappa = 0.39).

CONCLUSIONS

In our setting where QFT-IT is available but has limited use due to cost, TST with a cut-off of 10 mm for reactivity should be the initial LTB test. HIV-infected women and persons older than 52 years with non-reactive TST and long-term smokers with reactive TST may benefit from subsequent QFT-IT.

Comparison of the interferon-gamma release assay with the traditional methods for detecting Mycobacterium tuberculosis infection in children

The purpose of the article is to compare the whole blood interferon-γ release assay (IGRA) with the traditional methods for detecting Mycobacterium tuberculosis (MTB) infection in children. Fifteen childhood patients with tuberculosis and 15 healthy children were recruited. Sputa samples and venous blood were collected, and according to different procedures, IGRA, sputum smear, colloidal gold assay (CGA), fluorescence quantitation polymerase chain reaction (FQ-PCR), and tuberculosis skin test (TST) were, respectively, performed. Thirty healthy children vaccinated with Bacillus Calmette-Guérin (BCG) were also recruited, and the comparative test was carried out between IGRA and TST. In all of 15 childhood patients with TB, the positive rates were 86.7%, 20.0%, 26.7%, 40%, and 66.7% in IGRA, sputum smear, CGA, FQ-PCR, and TST, respectively. In the children vaccinated with BCG, the positive rate of IGRA was significantly lower than that of TST (6.7% vs 76.7%). From high to low, the specificities of the five methods were sputum smear (100%), IGRA (86.7%), FQ-PCR (86.7%), TST (40%), and CGA (26.7%). Although the specificities of sputum smear and FQ-PCR were more than or equal to that of IGRA, the relative sensitivities limited their applications in populations of children. IGRA is a sensitive and specific method, and could be taken as a first choice for detecting MTB infection in populations of children.

Latent Tuberculosis screening using interferon-gamma release assays in an Australian HIV-infected cohort: is routine testing worthwhile?

BACKGROUND

There are limited data from high-income countries on the performance of interferon-gamma release assays in screening for latent tuberculosis infection (LTBI). We analyzed the routine application of the Quantiferon-TB Gold (QFT-G) assay to detect and predict latent and active TB among HIV-infected patients in Australia.

METHODS

A retrospective cohort study included all HIV-infected patients attending the Melbourne Sexual Health Service between March 2003 and February 2011 who were screened for LTBI using QFT-G. Clinical data were analyzed in multivariable models to determine predictors for QFT-G positivity using logistic regression and active TB development using Cox proportional hazards.

RESULTS

Nine hundred seventeen HIV-infected patients had ≥1 QFT-G performed, of whom 884 (96.4%) were negative, 29 (3.2%) positive, and 4 (0.4%) indeterminate. The mean age was 40.9 years and 88% were male, with median follow-up of 26.4 (interquartile range 15.4-30.7) months. Five hundred fifty (63%) were Australian born, whereas 198 (23%) were born in Asia or Africa. QFT-G was positive in 2.0% of Australian-born, 5.3% of overseas-born [odds ratio: 2.6, 95% confidence interval (CI): 1.2 to 5.6, P = 0.017], and 12.7% of African-born patients (odds ratio 7.1, 95% CI: 2.9 to 17.3, P < 0.001). Two cases of culture-positive TB occurred after QFT-G screening in 3.4% of QFT-G-positive and 0.1% of QFT-G-negative patients (adjusted hazard ratio: 42.4, 95% CI: 2.2 to 827, P = 0.013), a rate of 111 (95% CI: 27.8 to 445) per 100,000 person-years.

CONCLUSIONS

In this context, QFT-G has a high negative predictive (99.9%) value with few indeterminate results. A risk stratification approach to LTBI screening, where HIV-infected patients with epidemiological risk factors for TB infection undergo QFT-G testing, might be clinically appropriate and potentially cost effective in similar settings.

Added value of QuantiFERON TB-gold in-tube for detecting latent tuberculosis infection among persons living with HIV/AIDS

OBJECTIVE

To evaluate the added value of QuantiFERON TB-Gold in-Tube (QTF-GIT) over the tuberculin skin testing (TST) for detecting latent tuberculosis (TB) infection (LTBI) among patients with AIDS in a city with a low TB incidence rate (11.1/100,000 inhabitants) and universal BCG coverage.

METHODS

Three hundred consecutive patients with AIDS in eight outpatient sexually transmitted disease public clinics in Brasilia were submitted to QFT-IT and TST between May 2011 and March 2013. A positive result of either test was considered to be LTBI.

RESULTS

Median CD4-cell count was 477.5 cells/mm(3); 295 (98.3%) were using antiretroviral therapy. Eighteen patients (6%, 95% CI: 3.6%-9.3%) had LTBI, of whom 4 (1.3%, 95% CI: 0.04%-2.63%) had only a positive TST, 8 (2.7%, 95% CI: 0.8%-4.5%) had only a QFT-GIT positive test, and 6 (2%, 95% CI: 0.4%-3.6%) had positive results for both tests. This represents an 81.8% relative increase in LTBI detection when QFT-GIT is added to TST. The concordance between both tests was 96% (k = 0.48).

CONCLUSIONS

The QFT-GIT alone was more effective to detect LTBI than TST alone and had an 81% added value as an add-on sequential test in this population with mild immunosuppression. The cost-effectiveness of these strategies remains to be evaluated.

Poor agreement between interferon-gamma release assays and the tuberculin skin test among HIV-infected individuals in the country of Georgia

BACKGROUND

Improved tests to diagnose latent TB infection (LTBI) are needed. We sought to evaluate the performance of two commercially available interferon-gamma release assays (IGRAs) compared to the tuberculin skin test (TST) for the diagnosis of LTBI and to identify risk factors for LTBI among HIV-infected individuals in Georgia, a country with high rates of TB.

METHODS

HIV-patients were enrolled from the National AIDS Center in Tbilisi, Georgia. After providing informed consent, each participant completed a questionnaire, had blood drawn for QuantiFERON-TB Gold in-Tube (QFT-GIT) and T-SPOT.TB testing and had a TST placed. The TST was read at 48-72 hrs with ≥ 5 mm induration considered positive.

RESULTS

Between 2009-2011, 240 HIV-infected persons (66% male) with a median age of 38 years and a median CD4 count of 255 cells/μl (IQR: 124-412) had diagnostic testing for LTBI performed. 94% had visible evidence of a BCG scar. The TST was positive in 41 (17%) patients; QFT-GIT in 70 (29%); and T-SPOT.TB in 56 (24%). At least one diagnostic test was positive in 109 (45%) patients and only among 13 (5%) patients were all three tests positive. Three (1%) QFT-GIT and 19 (8%) T-SPOT.TB test results were indeterminate. The agreement among all pairs of tests was poor: QFT-GIT vs. T-SPOT.TB (κ = 0.18, 95% CI .07-.30), QFT-GIT vs. TST (κ = 0.29, 95% CI .16-.42), and TST vs. T-SPOT.TB (κ = 0.22, 95% CI .07-.29). Risk factors for LTBI varied by diagnostic test and none showed associations between positive test results and well-known risk factors for TB, such as imprisonment, drug abuse and immunological status.

CONCLUSIONS

A high proportion of HIV patients had at least one positive diagnostic test for LTBI; however, there was very poor agreement among all tests. This lack of agreement makes it difficult to know which test is superior and most appropriate for LTBI testing among HIV-infected patients. While further follow-up studies will help determine the predictive ability of different LTBI tests, improved modalities are needed for accurate detection of LTBI and assessment of risk of developing active TB among HIV-infected patients.

Strategy to better select HIV-infected individuals for latent TB treatment in BCG-vaccinated population

Objective

To evaluate the T-SPOT.TB interferon-γ releasing assay and the tuberculin skin test (TST), for the diagnosis of latent tuberculosis infection(LTBI) and the development of subsequent active tuberculosis, in BCG-vaccinated HIV-infected individuals.

Methods

HIV-infected individuals without clinical suspicion of active TB or a past history of TB were enrolled from 1 January 2008 to 30 November 2010. Both T-SPOT.TB test and TST were offered to the participants whom were followed up prospectively until April 30, 2012 for development of TB.

Results

Among the 909 participants, 25% had positive TST reactions with cut-off point of 5 mm and 15% had positive T-SPOT.TB results. After a median follow-up of 2.97 years, there were 5 cases developed culture-confirmed active TB (all had dual positive TST and T-SPOT.TB results), and the incidence was 0.17 per 100 person-years. The relative risks (RRs) for subsequent active TB in HIV-infected individuals with positive TST results, positive T-SPOT.TB results and dual positive results compared with the risk for individuals with negative results were 40.6 (95% CI 2.1–767.9), 73.9 (95% CI 3.9–1397.7) and 226.5 (95% CI 12.0–4284), respectively. The number needed to treat to prevent one subsequent TB case among patients with a positive TST, a positive T-SPOT.TB and dual positive results was 35, 22 and 8 respectively.

Conclusions

Adopting positive results of the TST and T-SPOT.TB to screen LTBI among BCG-vaccinated HIV-infected individuals might be feasible. Number needed to treat for isoniazid preventive therapy could be reduced significantly by using dual positive strategy.

IFN-γ release assays in the diagnosis of latent tuberculosis infection among immunocompromised adults

Immunocompromised persons with latent tuberculosis infection (LTBI) are at increased risk for tuberculosis reactivation compared with the general population. The tuberculin skin test, the traditional assay for diagnosing LTBI, has reduced accuracy in immunocompromised patients. IFN-γ release assays (IGRAs) are in vitro blood tests that measure T-cell release of IFN-γ after stimulation with antigens unique to Mycobacterium tuberculosis. Here we review the data for the use of QuantiFERON-TB Gold In-Tube and T-SPOT.TB, the two currently available IGRAs, in immunocompromised adults, including persons infected with HIV, patients with immune-mediated inflammatory disorders, candidates for treatment with tumor necrosis factor-α inhibitors, patients receiving hemodialysis, solid-organ transplant recipients, and patients with cancer. On the basis of the available data, IGRAs have advantages over the tuberculin skin test in specific patient populations and in certain situations. Further studies are needed to more accurately define the usefulness of IGRAs in immunocompromised patients.

Interferon-Gamma Release Assays versus Tuberculin Skin Testing for the Diagnosis of Latent Tuberculosis Infection: An Overview of the Evidence

A profusion of articles have been published on the accuracy and uses of interferon-gamma releasing assays. Here we review the clinical applications, advantages, and limitations of the tuberculin skin test and interferon-gamma release assays and provide an overview of the most recent systematic reviews conducted for different indications for the use of these tests. We conclude that both tests are accurate to detect latent tuberculosis, although interferon-gamma release assays have higher specificity than tuberculin skin testing in BCG-vaccinated populations, particularly if BCG is received after infancy. However, both tests perform poorly to predict risk for progression to active tuberculosis. Interferon-gamma release assays have significant limitations in serial testing because of spontaneous variability and lack of a validated definition of conversion and reversion, making it difficult for clinicians to interpret changes in category (conversions and reversions). So far, the most important clinical evidence, that is, that isoniazid preventive therapy reduces the risk for progression to disease, has been produced only in tuberculin skin test-positive individuals.

Interferon gamma release assays for the diagnosis of latent TB infection in HIV-infected individuals in a low TB burden country

BACKGROUND

Interferon gamma release assays (IGRAs) are used to diagnose latent tuberculosis infection. Two IGRAs are commercially available: the Quantiferon TB Gold In Tube (QFT-IT) and the T-SPOT.TB. There is debate as to which test to use in HIV+ individuals. Previous publications from high TB burden countries have raised concerns that the sensitivity of the QFT-IT assay, but not the T-SPOT.TB, may be impaired in HIV+ individuals with low CD4+ T-cell counts. We sought to compare the tests in a low TB burden setting.

METHODOLOGY/PRINCIPAL FINDINGS

T-SPOT.TB, QFT-IT, and tuberculin skin tests (TST) were performed in HIV infected individuals. Results were related to patient characteristics. McNemar's test, multivariate regression and correlation analysis were carried out using SPSS (SPSS Inc). 256 HIV infected patients were enrolled in the study. The median CD4+ T-cell count was 338 cells/µL (range 1-1328). 37 (14%) patients had a CD4+ T-cell count of <100 cells/µL. 46/256 (18% ) of QFT-IT results and 28/256 (11%) of T-SPOT.TB results were positive. 6 (2%) of QFT-IT and 18 (7%) of T-SPOT.TB results were indeterminate. An additional 9 (4%) of T-SPOT.TB results were unavailable as tests were not performed due to insufficient cells or clotting of the sample. We found a statistically significant association between lower CD4+ T-cell count and negative QFT-IT results (OR 1.055, p=0.03), and indeterminate/unavailable T-SPOT.TB results (OR 1.079, p=0.02).

CONCLUSIONS/SIGNIFICANCE

In low TB prevalence settings, the QFT-IT yields more positive and fewer indeterminate results than T-SPOT.TB. Negative results on the QFT-IT and indeterminate/unavailable results on the T-SPOT.TB were more common in individuals with low CD4+ T-cell counts.

Tuberculosis skin test, but not interferon-γ-releasing assays is affected by BCG vaccination in HIV patients

OBJECTIVE

Of this study was to compare the results of tuberculin skin test (TST) with two interferon-γ releasing-assays (IGRA) in a cohort of HIV positive patients, to analyze impact of prior Bacille-Calmette-Guérin (BCG)-vaccination.

METHODS

Prospective cross sectional study, enrolling only asymptomatic adult HIV infected outpatients from a large German University hospital clinic. All participants were simultaneously tested for latent tuberculosis infection (LTBI) by QuantiFERON-TB Gold, T-SPOT.TB and TST. Only individuals with available definite results (positive/negative, indeterminates excluded) from all three test systems and recalling BCG-vaccination status by interview questionnaire were evaluated.

RESULTS

From 286 study participants, 133 were evaluable; BCG-vaccination history was positive for 18 individuals, and negative for 115. The proportion of individuals with a positive TST was significantly higher for vaccinated (n = 6, 33.3%) than for unvaccinated individuals (n = 13, 11.3%, p = 0.013). There were no significant differences in the proportion of patients with CDC stage C, origin from a TB endemic country or in the CD4 count between the two groups.

CONCLUSION

TST but not IGRAs interfered significantly with prior BCG vaccination in a cohort of HIV infected individuals from a low prevalence TB country. Therefore IGRA should preferentially be used for LTBI-testing in BCG-vaccinated adult HIV-patients.

Biomarkers of latent TB infection

For the last 100 years, the tuberculin skin test (TST) has been the only diagnostic tool available for latent TB infection (LTBI) and no biomarker per se is available to diagnose the presence of LTBI. With the introduction of M. tuberculosis-specific IFN-gamma release assays (IGRAs), a new area of in vitro immunodiagnostic tests for LTBI based on biomarker readout has become a reality. In this review, we discuss existing evidence on the clinical usefulness of IGRAs and the indefinite number of potential new biomarkers that can be used to improve diagnosis of latent TB infection. We also present early data suggesting that the monocyte-derived chemokine inducible protein-10 may be useful as a novel biomarker for the immunodiagnosis of latent TB infection.

Contribution of interferon gamma release assays testing to the diagnosis of latent tuberculosis infection in HIV-infected patients: a comparison of QuantiFERON-TB Gold In Tube, T-SPOT.TB and tuberculin skin test

BACKGROUND

Diagnosis and treatment of latent tuberculosis infection (LTBI) is the most effective strategy to control tuberculosis (TB) among patients with HIV infection. The tuberculin skin test (TST) was the only available method to identify LTBI. The aim of the present work was to evaluate the usefulness of the interferon-gamma release assays (IGRAs): QuantiFERON-tuberculosis (TB) Gold-In-Tube test (QFG) and T-SPOT.TB for the diagnosis of LTBI in a diverse cohort of HIV-infected patients.

METHODS

A prospective study was carried out in consecutive patients cared for in a single institution in Spain from January 2009 to October 2010. IGRAs and TST were performed simultaneously. TST induration ≥ 5 mm was considered positive.

RESULTS

QFG, T-SPOT.TB and TST were performed in 373 subjects. Median CD4 cell count was 470/μl with a median nadir of 150/μl. TST, QFG and T-SPOT.TB were positive in 13.3%, 7.5% and 18.5% cases respectively. Among 277 patients with neither past or current TB nor previous treatment for LTBI and who had TST results, a positive TST result was obtained in 20 (7.2%) cases. When adding QFG results to TST, there were a total of 26 (8.6%) diagnoses of LTBI. When the results of both IGRAs were added, the number of diagnoses increased to 54 (17.9%) (incremental difference: 10.7% [95% confidence interval [CI]:5.3-16.2%] [p < 0.001]), and when both IGRAs were added, the number of diagnoses reached 56 (18.5%) (incremental difference: 11.3% [95% CI:5.7%-16.9%] [p < 0.001]). Patients with a CD4 cell count greater than 500 cells/μl and prior stay in prison were more likely to have a diagnosis of LTBI by TST and/or QFG and/or T-SPOT.TB (adjusted odds ratio [aOR]: 3.8; 95% CI, 1.4 - 9.9; and aOR: 3.3; 95% CI, 1.3 - 8.3, respectively).

CONCLUSIONS

IGRAs were more sensitive than TST for diagnosis of M. tuberculosis infection in HIV-infected patients. Dual sequential testing with TST and IGRAs may be the optimal approach for LTBI screening in this population.

Factors associated with the performance of a blood-based interferon-γ release assay in diagnosing tuberculosis

Background

Indeterminate results are a recognised limitation of interferon-γ release assays (IGRA) in the diagnosis of latent tuberculosis (TB) infection (LTBI) and TB disease, especially in children. We investigated whether age and common co-morbidities were associated with IGRA performance in an unselected cohort of resettled refugees.

Methods

A retrospective cross-sectional study of refugees presenting for their post-resettlement health assessment during 2006 and 2007. Refugees were investigated for prevalent infectious diseases, including TB, and for common nutritional deficiencies and haematological abnormalities as part of standard clinical screening protocols. Tuberculosis screening was performed by IGRA; QuantiFERON-TB Gold in 2006 and QuantiFERON-TBGold In-Tube in 2007.

Results

Complete data were available on 1130 refugees, of whom 573 (51%) were children less than 17 years and 1041 (92%) were from sub-Saharan Africa. All individuals were HIV negative. A definitive IGRA result was obtained in 1004 (89%) refugees, 264 (26%) of which were positive; 256 (97%) had LTBI and 8 (3%) had TB disease. An indeterminate IGRA result was obtained in 126 (11%) refugees (all failed positive mitogen control). In multivariate analysis, younger age (linear OR  = 0.93 [95% CI 0.91–0.95], P<0.001), iron deficiency anaemia (2.69 [1.51–4.80], P = 0.001), malaria infection (3.04 [1.51–6.09], P = 0.002), and helminth infection (2.26 [1.48–3.46], P<0.001), but not vitamin D deficiency or insufficiency, were associated with an indeterminate IGRA result.

Conclusions

Younger age and a number of common co-morbidities are significantly and independently associated with indeterminate IGRA results in resettled predominantly African refugees.

Latent and subclinical tuberculosis in HIV infected patients: a cross-sectional study

BACKGROUND

HIV and tuberculosis (TB) are commonly associated. Identifying latent and asymptomatic tuberculosis infection in HIV-positive patients is important in preventing death and morbidity associated with active TB.

METHODS

Cross-sectional study of one time use of an interferon-gamma release assay (T-SPOT.TB - immunospot) to detect tuberculosis infection in patients in a UK inner city HIV clinic with a large sub-Saharan population.

RESULTS

542 patient samples from 520 patients who disclosed their symptoms of TB were tested. Median follow-up was 35 months (range 27-69). More than half (55%) originated from countries with medium or high tuberculosis burden and 57% were women. Antiretroviral therapy was used by 67%; median CD4 count at test was 458 cells/μl. A negative test was found in 452 samples and an indeterminate results in 40 (7.4%) but neither were associated with a low CD4 count. A positive test was found in 10% (50/502) individuals. All patients with positive tests were referred to the TB specialist, 47 (94%) had a chest radiograph and 46 (92%) attended the TB clinic. Two had culture-positive TB and a third individual with features of active TB was treated. 40 started and 38 completed preventive treatment. One patient who completed preventive treatment with isoniazid monotherapy subsequently developed isoniazid-resistant pulmonary tuberculosis. No patient with a negative test has developed TB.

CONCLUSIONS

We found an overall prevalence of latent TB infection of 10% through screening for TB in those with HIV infection and without symptoms, and a further 1% with active disease, a yield greater than typically found in contact tracing. Acceptability of preventive treatment was high with 85% of those with latent TB infection eventually completing their TB chemotherapy regimens. IGRA-based TB screening among HIV-infected individuals was feasible in the clinical setting and assisted with appropriate management (including preventive treatment and therapy for active disease). Follow-up of TB incidence in this group is needed to assess the long-term effects of preventive treatment.

Interferon-γ release assays for the diagnosis of tuberculosis and tuberculosis infection in HIV-infected adults: a systematic review and meta-analysis

BACKGROUND

Despite the widespread use of interferon-γ release assays (IGRAs), their role in diagnosing tuberculosis and targeting preventive therapy in HIV-infected patients remains unclear. We conducted a comprehensive systematic review to contribute to the evidence-based practice in HIV-infected people.

METHODOLOGY/PRINCIPAL FINDINGS

We searched MEDLINE, Cochrane, and Biomedicine databases to identify articles published between January 2005 and July 2011 that assessed QuantiFERON®-TB Gold In-Tube (QFT-GIT) and T-SPOT®.TB (T-SPOT.TB) in HIV-infected adults. We assessed their accuracy for the diagnosis of tuberculosis and incident active tuberculosis, and the proportion of indeterminate results. The search identified 38 evaluable studies covering a total of 6514 HIV-infected participants. The pooled sensitivity and specificity for tuberculosis were 61% and 72% for QFT-GIT, and 65% and 70% for T-SPOT.TB. The cumulative incidence of subsequent active tuberculosis was 8.3% for QFT-GIT and 10% for T-SPOT.TB in patients tested positive (one study each), and 0% for QFT-GIT (two studies) and T-SPOT.TB (one study) respectively in those tested negative. Pooled indeterminate rates were 8.2% for QFT-GIT and 5.9% for T-SPOT.TB. Rates were higher in high burden settings (12.0% for QFT-GIT and 7.7% for T-SPOT.TB) than in low-intermediate burden settings (3.9% for QFT-GIT and 4.3% for T-SPOT.TB). They were also higher in patients with CD4(+) T-cell count <200 (11.6% for QFT-GIT and 11.4% for T-SPOT.TB) than in those with CD4(+) T-cell count ≥ 200 (3.1% for QFT-GIT and 7.9% for T-SPOT.TB).

CONCLUSIONS/SIGNIFICANCE

IGRAs have suboptimal accuracy for confirming or ruling out active tuberculosis disease in HIV-infected adults. While their predictive value for incident active tuberculosis is modest, a negative QFT-GIT implies a very low short- to medium-term risk. Identifying the factors associated with indeterminate results will help to optimize the use of IGRAs in clinical practice, particularly in resource-limited countries with a high prevalence of HIV-coinfection.

Pulmonary infections in HIV-infected patients: an update in the 21st century

From the first descriptions of HIV/AIDS, the lung has been the site most frequently affected by the disease. Most patients develop a pulmonary complication during the history of HIV infection, mainly of infectious aetiology. Important changes in the epidemiology of HIV-related pulmonary infections have occurred. Overall, prescription of Pneumocystis jirovecii prophylaxis and the introduction of highly active antiretroviral therapy (HAART) are the main causes. Currently, the most frequent diagnosis in developed countries is bacterial pneumonia, especially pneumococcal pneumonia, the second most frequent cause is Pneumocystis pneumonia and the third is tuberculosis. However, in Africa, tuberculosis could be the most common pulmonary complication of HIV. Pulmonary infections remain one of the most important causes of morbidity and mortality in these patients, and the first cause of hospital admission in the HAART era. Achieving an aetiological diagnosis of pulmonary infection in these patients is important due to its prognostic consequences.

Improving the diagnosis of tuberculosis: From QuantiFERON to new techniques to diagnose tuberculosis infections

The diagnosis of latent and active tuberculosis in the HIV-positive population is challenged by diminished sensitivity of conventional tests, atypical presentations, and the lack of culture methods in the developing world, where the burden of co-infection is greatest. In response to these challenges, a variety of new diagnostics have emerged. These include interferon-gamma release assays for the diagnosis of latent tuberculosis (TB) infection and novel culture methods and molecular assays for the diagnosis of active tuberculosis. Although some tests (such as interferon-gamma release assays) are not clearly superior to existing diagnostics, other novel diagnostics, such as real-time polymerase chain reaction and the microscopic observed direct susceptibility assay hold much promise for prompt and accurate TB diagnosis in this population. Line-probe, nitrate reductase, and mycobacteriophage assays have also provided rapid alternatives to conventional time-consuming drug susceptibility testing and are critical to curtailing the spread of multidrug-resistant TB.

Improved sensitivity of an interferon-gamma release assay (T-SPOT.TB™) in combination with tuberculin skin test for the diagnosis of latent tuberculosis in the presence of HIV co-infection

BACKGROUND

Interferon-gamma release assays (IGRA) are more specific than the tuberculin skin test (TST) for the diagnosis of Mycobacterium tuberculosis infection. Data on sensitivity are controversial in HIV infection.

METHODS

IGRA (T-SPOT.TB) was performed using lymphocytes stored within 6 months before culture-confirmed tuberculosis was diagnosed in HIV-infected individuals in the Swiss HIV Cohort Study.

RESULTS

64 individuals (69% males, 45% of non-white ethnicity, median age 35 years (interquartile range [IQR] 31-42), 28% with prior AIDS) were analysed. Median CD4 cell count was 223 cells/μl (IQR 103-339), HIV-RNA was 4.7 log10 copies/mL (IQR 4.3-5.2). T-SPOT.TB resulted positive in 25 patients (39%), negative in 18 (28%) and indeterminate in 21 (33%), corresponding to a sensitivity of 39% (95% CI 27-51%) if all test results were considered, and 58% (95% CI 43-74%) if indeterminate results were excluded. Sensitivity of IGRA was independent of CD4 cell count (p = 0.698). Among 44 individuals with available TST, 22 (50%) had a positive TST. Agreement between TST and IGRA was 57% (kappa = 0.14, p = 0.177), and in 34% (10/29) both tests were positive. Combining TST and IGRA (at least one test positive) resulted in an improved sensitivity of 67% (95% CI 52-81%). In multivariate analysis, older age was associated with negative results of TST and T-SPOT.TB (OR 3.07, 95% CI 1,22-7.74, p = 0.017, per 10 years older).

CONCLUSIONS

T-SPOT.TB and TST have similar sensitivity to detect latent TB in HIV-infected individuals. Combining TST and IGRA may help clinicians to better select HIV-infected individuals with latent tuberculosis who qualify for preventive treatment.

Interferon-γ release assay for the diagnosis of latent tuberculosis in children younger than 5 years of age

BACKGROUND

There are limited data available on interferon-γ release assay (IGRA) performance in children up to 5 years of age, with documented exposure to active tuberculosis (TB). The aim of this study was to evaluate (1) the influence of infectivity of adult source cases on test results, (2) the impact of age, and (3) the level of agreement, between IGRA and tuberculin skin test (TST) results.

METHODS

A total of 142 Bacille Calmette-Guerin-vaccinated children up to 5 years of age were investigated because of a history of exposure to active TB. QuantiFERON-TB Gold In-Tube IGRA (QFT) and TST assays were performed.

RESULTS

Test results were significantly influenced by positive finding of cavitary lesions (QFT, odds ratio [OR] = 6.15; TST, OR = 7.48) and positive acid-fast bacilli (QFT, OR = 4.01; TST, OR = 4.47) in active TB contacts. QFT resulted in 1 indeterminate response (0.7%), attributable to low mitogen. There was no evidence for age having any effect on QFT performance. The 2 tests showed a moderate overall concordance (89%; κ = 0.591) at a TST cutoff value of ≥ 10 mm.

CONCLUSIONS

Association of positive QFT and TST results with risk factors for infection in child contacts (presence of cavitary lesions and acid-fast bacilli smear positivity in index cases) suggests that both the tests have good diagnostic accuracy. However, there was significant discord between results of the 2 tests that could not be definitively resolved. Thus, in a high-risk population of children up to 5 years of age, both tests (QFT and TST) should be performed and the child should be considered infected if either or both tests are positive.

Detection of latent tuberculosis by the tuberculin skin test and a whole-blood interferon-γ release assay, and the development of active tuberculosis in HIV-seropositive persons

This study evaluated the QuantiFERON-TB Gold In-Tube (QFT-GIT; Cellestis, Carnegie, Australia) test and the tuberculin skin test (TST) for the detection of latent tuberculosis infection (LTBI) in HIV-infected adults. One hundred thirty-five HIV-seropositive persons and 135 controls underwent TST and QFT-GIT. HIV-infected patients who gave a positive result on either test were offered chemoprophylaxis. The prevalence of LTBI was 6.7% by TST and 9.6% by QFT-GIT (P = 0.3) in HIV-seropositive subjects, and 34.8% by TST and 21.5% by QFT-GIT (P = 0.02) among controls. TST reactivity declined sharply as CD4(+) cells fell (15.8%, 10.3%, and 0% for >500, 301-500 and ≤300 CD4(+) cells/mm(3), respectively; P = 0.002). A less pronounced fall occurred with QFT-GIT (15.8%, 13.8%, and 0% for >500, 301-500, and <100 CD4(+) cells/mm(3), respectively; P = 0.03). No cases of tuberculosis occurred during follow-up (0.26 per 100 person-years). Simultaneous testing with TST and QFT-GIT for targeting of chemoprophylaxis, early in the course of HIV infection, might minimize the risk of tuberculosis in these patients.