Clinical Evaluation of a Line-Probe Assay for Tuberculosis Detection and Drug-Resistance Prediction in Namibia.

Treatment of tuberculosis requires rapid information about Mycobacterium tuberculosis (Mtb) drug susceptibility to ensure effective therapy and optimal outcomes. At the tuberculosis referral hospital in Windhoek, Namibia, a country of high tuberculosis incidence, we evaluated the diagnostic accuracy of a line-probe-assay (LPA), GenID, for the molecular diagnosis of Mtb infection and drug resistance in patients with suspected tuberculosis (cohort 1) and confirmed rifampin (RIF)-resistant tuberculosis (cohort 2). GenID test results were compared to Xpert MTB/RIF and/or Mtb culture and antimicrobial suceptibilty testing. GenID LPA was applied to 79 and 55 samples from patients in cohort 1 and cohort 2, respectively. The overall sensitivity of GenID LPA for the detection of Mtb DNA in sputum from patients with detectable and undetectable acid-fast bacilli by sputum smear microscopy was 93.3% (56/60; 95% confidence interval = 83.8-98.2) and 22.7% (5/22; 7.8-45.4). The sensitivity/specificity for the detection of drug resistance was 84.2% (32/38; 68.7-94.0)/100% (19/19; 82.4-100.0) for RIF, 89.7% (26/29; 72.6-97.8)/91.7% (22/24; 73.0-99.0) for isoniazid, and 85.7% (6/7; 42.1-99.6)/94.7% (18/19; 74.0-99.9) for fluoroquinolones; 23.6% of tests for second-line injectable resistance were invalid despite repeat testing. The diagnosis of tuberculosis by detection of Mtb DNA in sputum by GenID LPA depends strongly on the detection of acid-fast bacilli in sputum specimen. Prediction of drug resistance by GenID did not reach the World Health Organization (WHO) target product profile. IMPORTANCE Mycobacterium tuberculosis (Mtb) drug-resistance detection is crucial for successful control of tuberculosis. Line-probe assays (LPA) are frequently used to detect resistance to rifampin, isoniazid, fluoroquinolones (FQs), and second-line injectables (SLIs). GenID RIF/isoniazid (INH), FQ, and SLI LPA have not been widely tested and used so far. This study tested the diagnostic performance of the GenID LPA in a high-incidence TB/HIV, real-world setting in Namibia. The LPA demonstrates only an acceptable diagnostic performance for Mtb and drug-resistance detection. The diagnostic sensitivity and specificity fall short of the WHO suggested target product profiles for LPA.

Micronutrient supplementation and T cell-mediated immune responses in patients with tuberculosis in Tanzania.

Limited studies exist regarding whether incorporating micronutrient supplements during tuberculosis (TB) treatment may improve cell-mediated immune response. We examined the effect of micronutrient supplementation on lymphocyte proliferation response to mycobacteria or T-cell mitogens in a randomized trial conducted on 423 patients with pulmonary TB. Eligible participants were randomly assigned to receive a daily dose of micronutrients (vitamins A, B-complex, C, E, and selenium) or placebo at the time of initiation of TB treatment. We found no overall effect of micronutrient supplements on lymphocyte proliferative responses to phytohaemagglutinin or purified protein derivatives in HIV-negative and HIV-positive TB patients. Of HIV-negative TB patients, the micronutrient group tended to show higher proliferative responses to concanavalin A than the placebo group, although the clinical relevance of this finding is not readily notable. The role of nutritional intervention in this vulnerable population remains an important area of future research.

Performance of the Xpert® MTB/RIF assay in an active case-finding strategy: a pilot study from Tanzania.

In this pilot study, we evaluated the Xpert® MTB/RIF assay in an active case-finding strategy, using two spot sputum samples collected within a 1-hour interval from household contacts of smear-positive TB index cases. Tuberculosis (TB) confirmed by culture served as the reference standard. Among 219 enrolled contacts, the yield of active TB was 2.3%. While the sensitivity of smear microscopy was 60% (95%CI 14.7-94.7), Xpert MTB/RIF achieved a sensitivity of 100% (95%CI 47.81-100.0). All culture-confirmed cases tested positive by Xpert MTB/RIF on the first submitted sample, suggesting that the evaluation of only one sample could be sufficient for TB diagnosis in this context.

Anemia in adults with tuberculosis is associated with HIV and anthropometric status in Dar es Salaam, Tanzania.

SETTING: Tuberculosis (TB) infected adults attending out-patient TB clinics in Dar es Salaam, Tanzania. OBJECTIVE: To examine the association of anemia with human immunodeficiency virus (HIV) co-infection, indicators of socio-economic status (SES) and anthropometric status in TB-infected adults. DESIGN: Cross-sectional data collection during screening for a clinical trial. RESULTS: Overall, 750 females and 1693 males participated in this study, of whom respectively 49% and 24% were co-infected with HIV-1. Hemoglobin levels were significantly lower in females than in males and in HIV-positive than in HIV-negative participants. HIV co-infection in this antiretroviral-naïve population was also associated with severe anemia (hemoglobin < 85 g/l) in both women (prevalence ratio [PR] = 2.07, 95%CI 1.65-2.59) and men (PR 3.45, 95%CI 2.66-4.47). Although severe anemia was negatively associated with indicators of SES, especially in males, adjustment for SES indicators only marginally changed its association with HIV co-infection. In both sexes, anemia was inversely associated with anthropometric status, independently of HIV infection and SES. CONCLUSION: Among TB-infected adults, anemia is strongly associated with HIV co-infection and anthropometric status, independently of SES indicators. As anemia is a risk factor for morbidity and mortality in both infections, the management of anemia in TB-HIV co-infected patients warrants special attention.

Predictors of change in nutritional and hemoglobin status among adults treated for tuberculosis in Tanzania.

BACKGROUND: Patients with tuberculosis (TB) often suffer from profound malnutrition. OBJECTIVE: To examine the patterns and predictors of change in nutritional and hemoglobin status during and after TB treatment. METHODS: A total of 471 human immunodeficiency virus (HIV) positive and 416 HIV-negative adults with pulmonary TB were prospectively followed in Dar es Salaam, Tanzania. All patients received 8 months' TB treatment following enrollment. RESULTS: About 40% of HIV-positive and 47% of HIV-negative TB patients had body mass index (BMI) < 18.5 kg/m 2 at baseline, while about 94% of HIV-positive and 84% of HIV-negative participants were anemic at baseline. Both HIV-positive and HIV-negative patients experienced increases in BMI and hemoglobin concentrations over the course of TB treatment. Among HIV- positive patients, older age, low CD4 cell counts, and high viral load were independently associated with a smaller increase in BMI from baseline to 8 months. Fe- male sex, older age, low CD4 cell counts, previous TB infection and less money spent on food were independently associated with a smaller improvement in hemoglobin levels among HIV-positive patients during treatment. CONCLUSION: HIV-positive TB patients, especially those with low CD4 cell counts, showed poor nutritional recovery during TB treatment. Adequate nutritional support should be considered during TB treatment.

Evaluation of Diagnos TB AG, a flow-through immunoassay for rapid detection of pulmonary tuberculosis.

We evaluated the diagnostic performance of the Diagnos TB AG immunoassay in 171 Tanzanians with suspected pulmonary tuberculosis (TB). The sensitivity and specificity, and positive and negative predictive values of the rapid test for the detection of pulmonary TB in this population were respectively 60.0%, 33.3%, 40.3% and 52.6%. In its current configuration, this test will not help overcome difficulties in the rapid diagnosis of TB.

HIV co-infection, CD4 cell counts and clinical correlates of bacillary density in pulmonary tuberculosis.

BACKGROUND: Sputum microscopy for acid-fast bacilli (AFB) is the commonest diagnostic method for pulmonary tuberculosis (PTB) in developing countries. The method is reported to be less sensitive in human immunodeficiency virus (HIV) positive compared to negative patients. We determined the bacillary density in sputum of smear-positive PTB patients and related it to the patients' HIV status, CD4 cell count, clinical and demographic characteristics. METHODS: Three sputum samples per patient were examined using microscopy before initiating therapy. The AFB density was graded according to World Health Organization recommendations. The smear with the highest density was used. High bacillary density was defined as >10 AFB/field. HIV status and CD4 cell count were determined according to the national guidelines. RESULTS: Of 844 patients, 433 (51.3%) were HIV-positive. High bacillary density was significantly less common among HIV-positive (39.0%) than -negative (75.7%) patients (prevalence ratio 0.52; 95%CI 0.45-0.59, P < 0.0001). Among HIV-positive patients, the proportion of those with high bacillary density increased progressively with CD4 cell counts (P = 0.003). CONCLUSION: HIV is associated with lower AFB concentration in sputum. The AFB density falls with falling CD4 cell count. Microscopy for AFB in sputum may be less sensitive in diagnosing PTB when HIV infection is present, especially in severely immunocompromised patients.

Wasting and body composition of adults with pulmonary tuberculosis in relation to HIV-1 coinfection, socioeconomic status, and severity of tuberculosis.

OBJECTIVE: To examine the impact of HIV coinfection, socioeconomic status (SES) and severity of tuberculosis (TB) on the body composition and anthropometric status of adults with pulmonary TB. DESIGN: Cross-sectional study. SETTING: Five TB clinics in Dar es Salaam, Tanzania. SUBJECTS: A total of 2231 adult men and women diagnosed with pulmonary TB, prior to the initiation of anti-TB therapy. METHODS: We compared the distribution of anthropometric characteristics including body mass index (BMI), mid-upper arm circumference (MUAC), triceps skin-fold (TSF), and arm muscle circumference (AMC) by HIV status, SES characteristics, and indicators of TB severity (bacillary density in sputum and Karnofsky performance score). Similar comparisons were carried out with body composition variables from bioelectrical impedance analysis and albumin concentrations, in a subsample of 731 subjects. RESULTS: In multivariate analysis, HIV infection was significantly associated with lower MUAC and AMC in both men and women, but not with BMI or TSF. Compared to HIV-uninfected women, those who were HIV infected had lower body cell mass (BCM) (adjusted difference = -0.85 kg, P = 0.04), intracellular water (-0.68 l, P = 0.04), and phase angle (-0.52, P = 0.02). Albumin concentrations were significantly lower in both men and women infected with HIV. Among HIV-infected men, CD4 cell counts <200/mm(3) were related to lower intracellular water, BCM, fat-free mass and phase angle. Independent of HIV infection, BMI and MUAC were positively related to SES indicators and the Karnofsky performance score; and inversely related to bacillary density. CONCLUSIONS: HIV infection is associated with indicators of low lean body mass in adults with TB; socioeconomic factors and TB severity are important correlates of wasting, independent of HIV. SPONSORSHIP: The National Institute of Allergy and Infectious Diseases (UO1 AI 45441-01).