Tropical respiratory medicine. 2. Impact of human immunodeficiency virus on tuberculosis in developing countries

Timing of recurrence after treatment of pulmonary TB

Pulmonary TB (PTB) may recur due to reinfection or relapse after initial successful treatment. Based on microbiologically documented cases, we searched Embase, PubMed, Web of Science, and Medline for PTB recurrence. The timeframe of overall recurrences, relapse, reinfection, and risk factors were assessed. We compared the time to recurrence, relapse, and reinfection from treatment completion and plotted this using Kaplan-Meier curves. This systematic review included 23 articles describing 2,153 PTB recurrences in 75,224 treated people across all continents. Genotyping data to distinguish relapse from reinfection was available for 402 recurrences. The cumulative recurrence percentage was 2.9% over 5 years, and the median time for recurrence was 18 months (95% CI 16.99-19.0). Most recurrences (93%) were in HIV-negative people. Relapse occurred earlier than reinfection at 12 months (95% CI 10.86-13.14) vs 24 months (95% CI 21.61-26.39) (P < 0.001, χ2 59.89). In low TB burden settings, recurrences were mainly caused by relapse (85%), whereas in high-burden settings, relapses comprised 56% of recurrences. Recurrences occurred slightly earlier in HIV-positive patients (P = 0.038, χ2 4.30). The emergence of resistance to one or more first-line anti-TB agents was documented in 40 of 421 cases (9.5%). Early recurrences are mainly relapses, while late recurrences are mainly reinfections.

Varied trends of tuberculosis and HIV dual epidemics among different countries during 2000-2020: lessons from an ecological time-trend study of 9 countries

BACKGROUND

While Human Immunodeficiency Virus (HIV) infection is a well-established risk factor for tuberculosis (TB), the effect of HIV infection on TB incidence varies across countries given differences in local epidemiological factors and disparate progress with respect to TB elimination goals.

METHODS

In this descriptive epidemiological study, we explored the country-specific associations between HIV prevalence and TB incidence in nine countries representing four WHO regions using data between 2000 and 2020. For each of these countries, we (1) described the trends of TB incidence and HIV prevalence, and (2) examined country-level associations between TB incidence and HIV prevalence, using negative binomial regression.

RESULTS

The trends of TB incidence and HIV prevalence, and the country-level associations, varied across the study countries. Angola, Thailand and Zimbabwe showed parallel TB incidence and HIV prevalence trends while the two trends diverged in Brazil, Liberia and Indonesia during the study period. Additionally, the strength of association between HIV prevalence and TB incidence varied widely between countries, with the risk ratio ranging from 0.42 (95% CI: 0.36, 0.49) in Indonesia to 2.78 (95% CI: 2.57, 3.02) in Thailand.

CONCLUSIONS

The association of HIV infection with TB incidence varied across high burden settings, suggesting that HIV is not a ubiquitous driver of TB incidence. Without acknowledging the local drivers of TB epidemics across countries, the END TB Strategy cannot be adapted at the country level. The findings from this analysis can inform the design of future studies to identify country-specific drivers of TB using individual-level data.

Trends in Hospitalisation for Human Immunodeficiency Virus in a Tertiary Hospital in Dar es Salaam, Tanzania: A Case study

Background:

Reports on systematic evaluation of the impact of antiretroviral therapy(ART) on patients' hospitalisation in Sub Saharan Africa (SSA) and Tanzania in particular are scarce. We aimed at documenting the trends of hospital admissions at Muhimbili National Hospital (MNH) following scale up of free access to ART in Tanzania.

Methods:

Records for all admissions at MNH from June 2005 to June 2015 were reviewed. We extracted data from Hospital Information Management System as well as from patients' charts. Data extracted included diagnosis at discharge, reason for admission and thereafter assessed admission trends over the decade. We summarised the data as frequency and percentages. We compared proportions using Chi squared test, P<0.05 was deemed significant.

Results:

Overall there were 209,101 admissions during the study period (June 2005 to June 2015) and 7864/209,101 (3.8%) were due to HIV infection. Whereas 598/4,519 (13.2%) of all admissions in 2005 were due to HIV, only 345/13,119 (2.6%) of admissions in 2015 were HIV-related; showing a significant drop over time (P value for trend < .001). Generally, females 3887/6679 (58.2%) were more likely to be admitted than males (41.8%). Median CD4 count for admitted HIV patients was 143 cells/µl. Majority of admissions occured in the medical wards 3643/5310 (68.6%). Discharge diagnoses were Tuberculosis 1396/6482 (21.5%), anaemias 1016/6482 (15.6 %), malignancies 789/6482(12.2%), CNS infections 541/6482 (8.3%) and chronic kidney disease 308/6482 (4.8%). Three leading AIDS defining malignancies among hospitalised patients included Kaposi's sarcoma 380/789 (48.2%), carcinoma of the cervix 77/789 (9.8%), and Non-Hodgkin's lymphoma 44/789 (5.6%).

Conclusion:

Despite drastic drop of HIV related admissions at Muhimbili National Hospital over the years, the infection remains a problem of the adults, largely females suffering from medical conditions and presenting with severe immunosuppression. Tuberculosis remained the most common opportunistic infection among hospitalized HIV infected patients. Anaemia and cancers became more important causes of admission than was diarrhoea which had been the most common among HIV infected patients in pre- ART era.

Determinants of sputum smear nonconversion in smear-positive pulmonary tuberculosis patients in Suriname, 2010 - 2015

OBJECTIVE

To identify factors associated with sputum smear nonconversion in patients with pulmonary tuberculosis (PTB) in Suriname.

METHODS

A case-control study was conducted using routinely-collected surveillance data of PTB cases reported in January 2010 - December 2015 and recorded in the database of the National Tuberculosis Program of Suriname. Cases were smear-positive PTB patients whose sputum results were negative 2 months after treatment initiation. Controls were the smear-positive PTB patients whose sputum results were negative in the same timeframe. Multivariate logistic regression analysis was used to examine associations between potential risk factors and smear conversion.

RESULTS

The two age groups ≥ 35 years (35 - 54 years, AOR: 2.7, 95%CI: 1.2 - 6.1; and 55+ years, AOR: 2.5, 95%CI: 1.1 - 5.9) and high bacillary load at baseline (AOR 2.34, 95%CI: 1.2 - 4.8) were significantly associated with delayed smear conversion.

CONCLUSION

The National TB program of Suriname should develop strategies to address patients at higher risk for delayed smear conversion to prevent further spreading and unfavorable treatment outcomes. To better inform decision-making and future studies, the NTP should expand its data collection to include all risk factors for delayed smear conversion.

Diagnostic performance of automated liquid culture and molecular line probe assay in smear-negative pulmonary tuberculosis

The diagnosis of smear-negative pulmonary tuberculosis (PTB) is particularly challenging, and automated liquid culture and molecular line probe assays (LPA) may prove particularly useful. The objective of our study was to evaluate the diagnostic potential of automated liquid culture (ALC) technology and commercial LPA in sputum smear-negative PTB suspects. Spot sputum samples were collected from 145 chest-symptomatic smear-negative patients and subjected to ALC, direct drug susceptibility test (DST) testing and LPA, as per manufacturers' instructions. A diagnostic yield of 26.2% was observed among sputum smear-negative TB suspects with 47.4% of the culture isolates being either INH- and/or rifampicin-resistant. Complete agreement was observed between the results of ALC assay and LPA except for two isolates which demonstrated sensitivity to INH and rifampicin at direct DST but were rifampicin-resistant in LPA. Two novel mutations were also detected among the multidrug isolates by LPA. In view of the diagnostic challenges associated with the diagnosis of TB in sputum smear-negative patients, our study demonstrates the applicability of ALC and LPA in establishing diagnostic evidence of TB.

Predictors for MTB Culture-Positivity among HIV-Infected Smear-Negative Presumptive Tuberculosis Patients in Uganda: Application of New Tuberculosis Diagnostic Technology

Background

The existing World Health Organization diagnostic algorithms for smear-negative TB perform poorly in HIV-infected individuals. New TB diagnostics such as urine TB lipoarabinomannan (LAM) could improve the accuracy and reduce delays in TB diagnosis in HIV-infected smear-negative presumptive TB. We sought to determine predictors for MTB culture-positivity among these patients.

Methods

This study was nested into a prospective evaluation of HIV-infected outpatients and inpatients clinically suspected to have TB who were screened by smear-microscopy on two spot sputum samples. Data on socio-demographics, clinical symptoms, antiretroviral therapy, CXR, CD4 count, mycobacterial sputum and blood cultures and TB-LAM were collected. Logistic regression and conditional inference tree analysis were used to determine the most predictive indicators for MTB culture-positivity.

Results

Of the 418 smear-negative participants [female, 64%; median age (IQR) 32 (28-39) years, median CD4 106 (IQR 22 - 298) cells/mm³], 96/418 (23%) were sputum and/ or blood culture-positive for Mycobacterium tuberculosis (MTB) complex. Abnormal CXR (aOR 3.68, 95% CI 1.76- 7.71, p=0.001) and positive urine TB-LAM (aOR 6.21, 95% CI 3.14-12.27, p< 0.001) were significantly associated with MTB culture-positivity. Previous TB treatment (aOR 0.41, 95% CI 0.17-0.99, p=0.049) reduced the likelihood of a positive MTB culture. A conditional inference tree analysis showed that positive urine TB-LAM and abnormal CXR were the most predictive indicators of MTB culture-positivity. A combination of urine TB-LAM test and CXR had sensitivity and specificity of 50% and 86.1% respectively overall, and 70.8% and 84.1% respectively among those with CD4<100 cells/mm³.

Conclusions

A positive urine TB-LAM test and an abnormal CXR significantly predict MTB culture-positivity among smear-negative HIV-infected presumptive TB patients while previous TB treatment reduces the likelihood of a positive MTB culture. Validation studies to assess the performance of diagnostic algorithms that include urine TB-LAM in the diagnosis of smear-negative TB in HIV-infected individuals are warranted.

Tuberculosis and HIV Coinfection

Tuberculosis (TB) and human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) constitute the main burden of infectious disease in resource-limited countries. In the individual host, the two pathogens, Mycobacterium tuberculosis and HIV, potentiate one another, accelerating the deterioration of immunological functions. In high-burden settings, HIV coinfection is the most important risk factor for developing active TB, which increases the susceptibility to primary infection or reinfection and also the risk of TB reactivation for patients with latent TB. M. tuberculosis infection also has a negative impact on the immune response to HIV, accelerating the progression from HIV infection to AIDS. The clinical management of HIV-associated TB includes the integration of effective anti-TB treatment, use of concurrent antiretroviral therapy (ART), prevention of HIV-related comorbidities, management of drug cytotoxicity, and prevention/treatment of immune reconstitution inflammatory syndrome (IRIS).

Predictors and outcomes of mycobacteremia among HIV-infected smear- negative presumptive tuberculosis patients in Uganda

BACKGROUND

Sputum smear microscopy for tuberculosis (TB) diagnosis lacks sensitivity in HIV-infected symptomatic patients and increases the likelihood that mycobacterial infections particularly disseminated TB will be missed; delays in diagnosis can be fatal. Given the duration for MTB growth in blood culture, clinical predictors of MTB bacteremia may improve early diagnosis of mycobacteremia. We describe the predictors and mortality outcome of mycobacteremia among HIV-infected sputum smear-negative presumptive TB patients in a high prevalence HIV/TB setting.

METHODS

Between January and November 2011, all consenting HIV-infected adults suspected to have TB (presumptive TB) were consecutively enrolled. Diagnostic assessment included sputum smear microscopy, urine Determine TB lipoarabinomannan (LAM) antigen test, mycobacterial sputum and blood cultures, chest X-ray, and CD4 cell counts in addition to clinical and socio-demographic data. Patients were followed for 12 months post-enrolment.

RESULTS

Of 394 sputum smear-negative participants [female, 63.7%; median age (IQR) 32 (28-39) years], 41/394 (10.4%) had positive mycobacterial blood cultures (mycobacteremia); all isolates were M. tuberculosis (MTB). The median CD4 cell count was significantly lower among patients with mycobacteremia when compared with those without (CD4 31 versus 122 cells/μL, p < 0.001). In a multivariate analysis, male gender [OR 3.4, 95%CI (1.4-7.6), p = 0.005], CD4 count <100 cells/μL [OR 3.1, 95% CI (1.1-8.6), p = 0.030] and a positive lateral flow urine TB LAM antigen test [OR 15.3, 95%CI (5.7-41.1), p < 0.001] were significantly associated with mycobacteremia. At 12 months of follow-up, a trend towards increased mortality was observed in patients that were MTB blood culture positive (35.3%) compared with those that were MTB blood culture negative (23.3%) (p = 0.065).

CONCLUSIONS

Mycobacteremia occurred in 10% of smear-negative patients and was associated with higher mortality compared with smear-negative patients without mycobacteremia. Advanced HIV disease (CD4 < 100 cells/mm(3)), male gender and positive lateral flow urine TB LAM test predicted mycobacteremia in HIV-infected smear-negative presumptive TB patients in this high prevalence TB/HIV setting.

Impact of co-infections and BCG immunisation on immune responses among household contacts of tuberculosis patients in a Ugandan cohort

BACKGROUND

Tuberculosis incidence in resource poor countries remains high. We hypothesized that immune modulating co-infections such as helminths, malaria, and HIV increase susceptibility to latent tuberculosis infection (LTBI), thereby contributing to maintaining the tuberculosis epidemic.

METHODS

Adults with sputum-positive tuberculosis (index cases) and their eligible household contacts (HHCs) were recruited to a cohort study between May 2011 and January 2012. HHCs were investigated for helminths, malaria, and HIV at enrolment. HHCs were tested using the QuantiFERON-TB Gold In-Tube (QFN) assay at enrolment and six months later. Overnight whole blood culture supernatants from baseline QFN assays were analyzed for cytokine responses using an 11-plex Luminex assay. Associations between outcomes (LTBI or cytokine responses) and exposures (co-infections and other risk factors) were examined using multivariable logistic and linear regression models.

RESULTS

We enrolled 101 index cases and 291 HHCs. Among HHCs, baseline prevalence of helminths was 9% (25/291), malaria 16% (47/291), HIV 6% (16/291), and LTBI 65% (179/277). Adjusting for other risk factors and household clustering, there was no association between LTBI and any co-infection at baseline or at six months: adjusted odds ratio (95% confidence interval (CI); p-value) at baseline for any helminth, 1.01 (0.39-2.66; 0.96); hookworm, 2.81 (0.56-14.14; 0.20); malaria, 1.06 (0.48-2.35; 0.87); HIV, 0.74 (0.22-2.47; 0.63). HHCs with LTBI had elevated cytokine responses to tuberculosis antigens but co-infections had little effect on cytokine responses. Exploring other risk factors, Th1 cytokines among LTBI-positive HHCs with BCG scars were greatly reduced compared to those without scars: (adjusted geometric mean ratio) IFNγ 0.20 (0.09-0.42), <0.0001; IL-2 0.34 (0.20-0.59), <0.0001; and TNFα 0.36 (0.16-0.79), 0.01.

CONCLUSIONS

We found no evidence that co-infections increase the risk of LTBI, or influence the cytokine response profile among those with LTBI. Prior BCG exposure may reduce Th1 cytokine responses in LTBI.

Clinical predictors and accuracy of empiric tuberculosis treatment among sputum smear-negative HIV-infected adult TB suspects in Uganda

Introduction

The existing diagnostic algorithms for sputum smear-negative tuberculosis (TB) are complicated, time-consuming, and often difficult to implement. The decision to initiate TB treatment in resource-limited countries is often largely based on clinical predictors. We sought to determine the clinical predictors and accuracy of empiric TB treatment initiation in HIV-infected sputum smear-negative TB suspects using sputum culture as a reference standard.

Setting

Out-patient HIV-TB integrated urban clinic in Kampala, Uganda.

Methods

HIV-infected TB suspects were screened using sputum smear microscopy, and mycobacterial sputum liquid and solid cultures were performed. Smear results were made available to the clinician who made a clinical decision on empiric TB treatment initiation for sputum smear-negative patients. Clinic records were reviewed for patients whose sputum smears were negative to collect data on socio-demographics, TB symptomatology, chest X-ray findings, CD4 cell counts and TB treatment initiation.

Results

Of 253 smear-negative TB suspects, 56% (142/253) were females, median age 38 IQR (31–44) years, with a median CD4 cell count of 291 IQR (150–482) cells/mm³. Of the 85 (33.6%) smear-negative patients empirically initiated on TB treatment, 35.3% (n = 30) were sputum culture positive compared to only 18 (10.7%) of the 168 untreated patients (p<0.001). Abnormal chest X-ray [aOR 10.18, 95% CI (3.14–33.00), p<0.001] and advanced HIV clinical stage [aOR 3.92, 95% CI (1.20–12.85), p = 0.024] were significantly associated with empiric TB treatment initiation. The sensitivity and specificity of empiric TB treatment initiation in the diagnosis of TB in HIV-infected patients after negative smear microscopy was 62.5% and 73.7% respectively.

Conclusion

In resource-limited settings, clinically advanced HIV and abnormal chest X-ray significantly predict a clinical decision to empirically initiate TB treatment in smear-negative HIV-infected patients. Empiric TB treatment initiation correlates poorly with TB cultures. Affordable, accurate and rapid point-of-care diagnostics are needed in resource-limited settings to more accurately determine which HIV-infected TB suspects have smear-negative TB.

Performance of the new WHO diagnostic algorithm for smear-negative pulmonary tuberculosis in HIV prevalent settings: a multisite study in Uganda

OBJECTIVE

To compare the performance of the new WHO (2007) diagnostic algorithm for pulmonary tuberculosis (PTB) in high HIV prevalent settings (WHO07) to the WHO 2003 guidelines used by the Ugandan National Tuberculosis Program (UgWHO03).

METHODS

A prospective observational cohort design was used at Reach Out Mbuya Parish HIV/AIDS Initiative, an urban slum community-based AIDS Service Organisation (ASO) and Kayunga Rural District Government Hospital. Newly diagnosed and enrolled HIV-infected patients were assessed for PTB. Research staff interviewed patients and staff and observed operational constraints.

RESULTS

WHO07 reduced the time to diagnosis of smear-negative PTB with increased sensitivity compared with the UgWHO03 at both sites. Time to diagnosis of smear-negative PTB was significantly shorter at the urban ASO than at the rural ASO (12.4 vs. 28.5 days, P = 0.003). Diagnostic specificity and sensitivity [95% confidence intervals (CIs)] for smear-negative PTB were higher at the rural hospital compared with the urban ASO: [98% (93-100%) vs. 86% (77-92%), P = 0.001] and [95% (72-100%) vs. 90% (54-99%), P > 0.05], respectively. Common barriers to implementation of algorithms included failure by patients to attend follow-up appointments and poor adherence by healthcare workers to algorithms.

CONCLUSION

At both sites, WHO07 expedited diagnosis of smear-negative PTB with increased diagnostic accuracy compared with the UgWHO03. The WHO07 expedited diagnosis more at the urban ASO but with more diagnostic accuracy at the rural hospital. Barriers to implementation should be taken into account when operationalising these guidelines for TB diagnosis in resource-limited settings.

Implementation of the thin layer agar method for diagnosis of smear-negative pulmonary tuberculosis in a setting with a high prevalence of human immunodeficiency virus infection in Homa Bay, Kenya

The objective of this study was to evaluate the performance of a low-cost method, the thin layer agar (TLA) method, for the diagnosis of smear-negative patients. This prospective study was performed in Homa Bay District Hospital in Kenya. Out of 1,584 smear-negative sputum samples, 212 (13.5%) were positive by culture in Löwenstein-Jensen medium (LJ) and 220 (14%) were positive by the TLA method. The sensitivities of LJ and TLA were 71% and 74%, respectively. TLA could become an affordable method for the diagnosis of smear-negative tuberculosis in resource-limited settings, with results available within 2 weeks.

Resistência do Mycobacterium tuberculosis às drogas em pacientes HIV+ em cinco municípios da Baixada Santista, São Paulo, Brasil

No início dos anos 90, observou-se aumento da resistência do Mycobacterium tuberculosis às drogas antituberculose, com alta prevalência entre pacientes HIV+. Neste estudo, foram avaliados a freqüência de resistência, o perfil de sensibilidade do M. tuberculosis às drogas e os fatores predisponentes à resistência entre indivíduos HIV+ nos municípios de Santos, São Vicente, Cubatão, Praia Grande e Guarujá, Estado de São Paulo, Brasil. Foram pesquisados os prontuários de 301 pacientes com resultado de cultura positivo entre 1993 e 2003. A resistência ocorreu em 57 (18,9%) pacientes com a seguinte distribuição: 32 (10,6%) apresentaram tuberculose multirresistente (resistência ao menos à Rifampicina e Isoniazida); 4 (1,3%) casos apresentaram resistência a duas ou mais drogas e 21 (7%) à monorresistência. Observou-se resistência secundária em 70,2% dos casos. Estatisticamente associadas à tuberculose resistente foram: tratamento anterior com drogas antituberculose, tempo de diagnóstico de HIV e hospitalização prévia. Em análise multivariada, apenas tratamento anterior, ajustado por faixa etária, mostrou-se associado (OR = 5,49; IC95%: 2,60-11,60). A ocorrência de resistência em 18,9% dos casos e multirresistência em aproximadamente 10% confirmam a relevância deste problema entre pacientes HIV+ na Baixada Santista.

High rates of clinical and subclinical tuberculosis among HIV-infected ambulatory subjects in Tanzania

BACKGROUND

We sought to determine the prevalence of active tuberculosis among ambulatory HIV-infected persons in Tanzania with CD4 cell counts of > or =200 cells/mm3 and a bacille Calmette-Guerin vaccination scar.

METHODS

Subjects who volunteered for a tuberculosis booster vaccine trial were screened for active tuberculosis by obtainment of a history, physical examination, chest radiography, sputum culture and acid fast bacillus (AFB) stain, and blood culture. All subjects underwent a tuberculin skin test (TST) and lymphocyte proliferation assays (LPAs) for detection of responses to mycobacterial antigens.

RESULTS

Active tuberculosis was identified at baseline in 14 (15%) of the first 93 subjects who were enrolled: 10 (71%) had clinical tuberculosis (symptoms or chest radiograph findings), and 4 (29%) had subclinical tuberculosis (positive sputum AFB stain or culture results but no symptoms or chest radiograph findings). An additional 6 subjects with subclinical tuberculosis were identified subsequently. The 10 subjects with subclinical tuberculosis included 3 with positive sputum AFB stains results and 7 who were only identified by a positive sputum culture result. Compared with subjects who did not have tuberculosis, the 10 subjects with subclinical tuberculosis were more likely to have peripheral lymphadenopathy, positive TST results, and elevated LPA responses to early secreted antigenic target-6 (ESAT). Eight of 10 patients had received isoniazid because of a positive TST result before active tuberculosis was recognized.

CONCLUSIONS

Clinical and subclinical tuberculosis are common among ambulatory HIV-infected persons, and some cases can only be identified by sputum culture. World Health Organization guidelines for screening for latent tuberculosis before treatment do not recommend sputum culture and, therefore, may fail to identify a substantial number of HIV-infected persons with subclinical, active tuberculosis.

Molecular epidemiology study of exogenous reinfection in an area with a low incidence of tuberculosis

In geographical areas with a low incidence of tuberculosis, recurrent tuberculosis is generally due to reactivation of the disease. However, the relative contribution of tuberculosis reinfection increases in parallel with the incidence of disease and is likely to depend on the epidemiological context: factors such as the spread of multidrug resistance, human immunodeficiency virus (HIV) infection, and immigration from developing countries could modify disease transmission in areas at low risk for tuberculosis. A molecular epidemiology study was performed in Lombardy, Northern Italy, where the incidence of tuberculosis is 17.5 cases per 100,000 persons. A total of 2,452 cases of culture-confirmed tuberculosis in 2,127 patients were studied. A group of 32 patients (1.5%), each of whom had two episodes of tuberculosis with cure as the outcome of the first episode and with more than 6 months between the two episodes, were studied by means of restriction fragment length polymorphism DNA fingerprinting analysis. For 5 of the 32 patients (16%), the DNA fingerprinting patterns of Mycobacterium tuberculosis strains responsible for the second episode did not match those of the corresponding isolates of the first episode, indicating exogenous reinfection. Two of these patients developed multidrug-resistant tuberculosis during the second episode, and in three cases the isolates belonged to clusters of M. tuberculosis strains spreading in the community. A fourfold-increased risk for reinfection was observed in immigrant patients compared to Italian subjects. In contrast, a higher risk of relapse rather than reinfection was evidenced in HIV-positive subjects and in patients infected with multidrug-resistant tuberculosis. Episodes of tuberculosis reinfection in areas with a low incidence of tuberculosis are rare compared to those in high-incidence geographical regions. In populations that have immigrated from high-risk areas, reinfection may represent a considerable contributor to the rate of recurrent tuberculosis. This finding emphasizes the importance of containing the spread of epidemic strains in close communities, in order to prevent changes in global tuberculosis trends for developed countries.

Sputum concentration improves diagnosis of tuberculosis in a setting with a high prevalence of HIV

Sputum microscopy for acid-fast bacilli (AFB), although relatively insensitive, is still the cornerstone of tuberculosis (TB) diagnosis in the developing world. Its diagnostic value has been eroded owing to the increasing number of HIV-related smear-negative pulmonary TB cases. Concentration of sputum by centrifugation after liquefaction with sodium hypochlorite is a possible means of increasing the sensitivity of direct microscopy. This procedure has been studied recently in developing countries although with conflicting results. The aim of our study, performed in 1996 in Addis Ababa, Ethiopia, was to evaluate the sensitivity of the concentration method in a large cohort of consecutive patients with suspected pulmonary TB. We show that the overall sensitivity increased from 54.2% using conventional direct microscopy to 63.1% after concentration (P < 0x0015). In HIV-positive patients, sensitivity increased from 38.5% before to 50.0% after concentration (P < 0x0034). The significant increase in yield of AFB in HIV-positive patients suggests that this method has a place in routine diagnosis of pulmonary TB in countries with a high prevalence of HIV.

Risk factors for tuberculosis among human immunodeficiency virus-infected persons. A case-control study in Belo Horizonte, Minas Gerais, Brazil (1985-1996)

The objective of this study was to identify tuberculosis risk factors and possible surrogate markers among human immunodeficiency virus (HIV)-infected persons. A retrospective case-control study was carried out at the HIV outpatient clinic of the Universidade Federal de Minas Gerais in Belo Horizonte. We reviewed the demographic, social-economical and medical data of 477 HIV-infected individuals evaluated from 1985 to 1996. The variables were submitted to an univariate and stratified analysis. Aids related complex (ARC), past history of pneumonia, past history of hospitalization, CD4 count and no antiretroviral use were identified as possible effect modifiers and confounding variables, and were submitted to logistic regression analysis by the stepwise method. ARC had an odds ratio (OR) of 3.5 (CI 95% - 1.2-10.8) for tuberculosis development. Past history of pneumonia (OR 1.7 - CI 95% 0.6-5.2) and the CD4 count (OR 0.4 - CI 0. 2-1.2) had no statistical significance. These results show that ARC is an important clinical surrogate for tuberculosis in HIV-infected patients. Despite the need of confirmation in future studies, these results suggest that the ideal moment for tuberculosis chemoprophylaxis could be previous to the introduction of antiretroviral treatment or even just after the diagnosis of HIV infection.

Human immunodeficiency virus and the outcome of treatment for new and recurrent pulmonary tuberculosis in African patients

The purpose of this study was to evaluate the impact of human immunodeficiency virus (HIV) infection on treatment for tuberculosis (TB). The study population comprised 28,522 black Southern African gold miners. Patients with sputum culture-positive new or recurrent pulmonary TB diagnosed in 1995 were prospectively enrolled in the cohort. Directly observed therapy (DOT) was practiced and outcomes were assessed at 6 mo after treatment was begun. There were 376 cases of TB (incidence 1,318 per 100,000), of which 190 (50%) were HIV positive and 82 (22%) had recurrent TB. There was no association between HIV status and history of previous TB or drug resistance. Neither the treatment interruption rate (2%) nor the rate at which patients transferred out of the treatment program (1.6%) were associated with HIV status. Excluding deaths, cure rates were similar for HIV-positive and HIV-negative patients (89% versus 88%), but significantly lower in those with recurrent than in those with new TB (77% versus 92%). Mortality was 0.5% in HIV-negative patients versus 13.7% in HIV-positive patients, and in the latter group was associated with CD4(+) lymphocyte depletion. Autopsy examination showed that in HIV-positive patients, early mortality was due to TB whereas late deaths were most commonly due to cryptococcal pneumonia. The study showed that a well-run TB control program can result in acceptable cure rates even in a population with a very high incidence of TB and HIV infection. Particular vigilance is needed for concurrent infections, which may contribute significantly to mortality during treatment of TB in HIV-positive patients.

HIV-testing study of immigrants with pulmonary tuberculosis

The increasing prevalence of tuberculosis (TB) and human immunodeficiency virus (HIV), particularly in Africa and Asia, led us to investigate the prevalence of HIV infection in immigrants with pulmonary TB at the time of arrival in the UK. We performed anonymous HIV testing of stored sera from 39/65 immigrants referred to our unit between January 1991 and December 1994, who had culture-positive pulmonary TB. None of the 39 patients tested was positive for either HIV-1 or HIV-2, and the characteristics of the 26 patients for whom no serum was available were similar to those of the tested group. Despite the need to consider concomitant HIV infection in any patient with TB, particularly those from an area of HIV endemnicity, the present data do not suggest that recently arrived refugees, asylum seekers, immigrants or long-term visitors to the UK constitute a group in whom dual infection of HIV and Mycobacterium tuberculosis is common.

Tuberculosis and HIV infection: global perspectives

This paper reviews the epidemiological and clinical aspects of the interaction between Mycobacterium tuberculosis and HIV infection. The incidence of HIV-associated tuberculosis is increasing worldwide and is expected to increase further, especially in Africa and parts of Asia. HIV infection appears to increase the likelihood that tuberculous infection will occur after tubercle bacilli are inhaled into the lungs. Moreover, there is persuasive evidence that in the presence of HIV infection, new-onset tuberculous infection will progress rapidly to clinically significant disease and the probability that latent tuberculous infection will reactivate is enormously increased. The accelerating and amplifying influence of HIV infection is also contributing to the increasing incidence of disease caused by multidrug-resistant strains of M. tuberculosis. Neither clinical nor radiographic features reliably distinguish the majority of patients with HIV-associated tuberculosis from those who are non-HIV-infected. Some HIV-infected patients, however, have atypical manifestations and are difficult to diagnose. Chemotherapy for 6 months with conventional antituberculosis drugs cures most patients, but many died during or after treatment of other AIDS-related complications. HIV is contributing heavily to the worldwide increase in tuberculosis. There is also mounting evidence that tuberculosis accelerates the course of co-existing HIV disease.

Ocular tuberculosis. A prospective study in a general hospital

Ocular tuberculosis has traditionally been considered uncommon or anecdotal. Imprecise and variable diagnostic criteria have contributed to the confusion surrounding this topic. The increase in extrapulmonary manifestations of tuberculosis during the AIDS era established the need for a prospective study of ocular involvement in patients with all types of tuberculosis using well-defined criteria. During a 15-month period, 300 cases had culture-proven tuberculosis at our institution. We randomly selected 100 for systematic ophthalmologic evaluation. Our criteria for ocular tuberculosis were divided as follows: certainty (isolation of Mycobacterium tuberculosis from ocular specimens), probability (patients with isolation of M. tuberculosis from extraocular samples, with ocular lesions not attributable to other causes that respond to anti-tuberculous treatment), and possibility (same as probability but follow-up impossible). Ocular tuberculosis was present in 18 patients (18%) of which 10 patients fulfilled probability and 8 patients fulfilled possibility criteria. Eleven of 18 patients had HIV infection. In 11 patients, ocular involvement was asymptomatic. Almost all patients (17/18) had choroiditis, and other ocular lesions included papillitis, retinitis, vitritis, vasculitis, dacryoadenitis, and scleritis. Multivariate analysis showed as risk factors independently predicting ocular involvement in patients with ocular tuberculosis the presence of miliary disease (odd ratio 43.92, p = 0.002), ocular symptoms (odds ratio 6.35, p = 0.0143), and decreased visual acuity (odds ratio 0.04, p = 0.012). We observed an unexpectedly high (18%) incidence of ocular involvement, frequently asymptomatic, in patients with tuberculosis. Miliary disease is a clear predisposing factor in both HIV-infected and noninfected populations. Ocular examination should be routinely considered in patients with proven or suspected tuberculosis.

Tuberculosis in Africa: clinical presentation and management

In the last decade, sub-Saharan Africa has experienced an explosive increase in tuberculosis (TB) cases, largely as a result of the co-epidemic of human immunodeficiency virus (HIV) infection. This article reviews the essential background epidemiology of TB in sub-Saharan Africa. The clinical features and diagnostic problems of pulmonary/extrapulmonary TB in adults and children are discussed, particularly in relation to HIV infection. Different treatment regimens, their cost, adverse reactions, the ways in which HIV infection influences treatment response and the extent of drug resistance are reviewed. The recommended approaches to TB control in Africa, including methods used to prevent TB through Bacillus Calmette-Guerin and chemoprophylaxis are examined. The success achieved by good National TB Control Programmes in some African countries allows cautious optimism that this epidemic can be controlled.

Mycobacterial complications of HIV infection

Tuberculosis is the most common opportunistic infection worldwide and is caused by the only readily transmissible pathogen among persons with HIV infection. If treatment is initiated promptly and is supervised appropriately, cure, fortunately, is highly likely. Isoniazid preventive therapy substantially reduces the risk of tuberculosis in persons with HIV infection. Of the nontuberculous mycobacteria, Mycobacterium avium complex (MAC) is the most frequent cause of disease; however, disseminated MAC disease usually is not seen until the CD4+ cell count is less than 50 cells/L. Newer agents, such as the macrolides and rifabutin, form the nucleus of treatment regimens and also are effective in preventing the disease.