A rapid and low-cost microscopic observation drug susceptibility assay for detecting TB and MDR-TB among individuals infected by HIV in South India.

Background: The converging epidemics of HIV and tuberculosis (TB) pose one of the greatest public health challenges of our time. Rapid diagnosis of TB is essential in view of its infectious nature, high burden of cases, and emergence of drug resistance. Objective: The purpose of this present study was to evaluate the feasibility of implementing the microscopic observation drug susceptibility (MODS) assay, a novel assay for the diagnosis of TB and multi-drug-resistant tuberculosis (MDR-TB) directly from sputum specimens, in the Indian setting. Materials and Methods: This study involved a cross-sectional, blinded assessment of the MODS assay on 1036 suspected cases of pulmonary TB in HIV-positive and HIV-negative patients against the radiometric method, BD-BACTEC TB 460 system. Results: Overall, the sensitivity, specificity, positive predictive value, and negative predictive value of the MODS assay in detecting MTB among TB suspected patients were 89.1%, 99.1%, 94.2%, 95.8%, respectively. In addition, in the diagnosis of drug-resistant TB, the MODS assay was 84.2% sensitive for those specimens reporting MDR, 87% sensitivity for those specimens reporting INH mono-resistance, and 100% sensitive for specimens reporting RIF mono-resistance. The median time to detection of TB in the MODS assay versus BACTEC was 9 versus 21 days (P < 0.001). Conclusion: Costing 5 to 10 times lesser than the automated culture methods, the MODS assay has the potential clinical utility as a simple and rapid method. It could be effectively used as an alternative method for diagnosing TB and detection of MDR-TB in a timely and affordable way in resource-limited settings.

Evaluation of two indigenous rapid and two ELISA assays for the diagnosis of HIV infection India.

Purpose: Human immunodeficiency virus (HIV) diagnostic tests are being used extensively in India. However, the evaluation data on these assays are very limited. The present study evaluates indigenous HIV test kits manufactured in India. Materials and Methods: A total of 200 characterised specimens were assayed with Comb AIDS - RS Advantage HIV 1+2 Immunodot Test, Enzaids HIV 1+2 ELISA test, Enzaids Duet HIV Antigen+antibody ELISA test and Signal HIV Flow Through HIV 1+2 test kits. Performance characteristics of these assays were calculated. Results: Sensitivity, specificity, positive predictive value, negative predictive value and efficiency of all the assays were 100% except for Signal HIV Flow Through HIV 1+2 test kit. The specificity, positive predictive value and efficiency of the Signal HIV Flow Through HIV 1+2 test kit were 98.9%, 98.9% and 99.4%, respectively. The Enzaids Duet HIV kit was found to be extremely sensitive in detecting p24 Ag with the sensitivity of 1.5 pg/mL. Conclusions: To conclude, selection of better diagnostic assay is very much important to resolve discrepancies in HIV diagnosis. All these assays under evaluation in this report have got excellent performance characteristics and much suitable to use in serial testing algorithms in use for resources limited settings.

Establishment of T-lymphocyte subset reference intervals in a healthy adult population in Chennai, India.

Estimation of CD4+ T-lymphocytes continues to be an important aspect for monitoring HIV disease progression and response to antiretroviral therapy. Most of the diagnostic laboratories often rely on western text books for CD4+ T-lymphocyte reference values, which could, often be unreliable for usage in local settings. Therefore, we attempted to establish the reference values for T-lymphocyte subsets among healthy adults in a cross-sectional study carried out at the YRG Centre for AIDS Research and Education (YRG CARE) in Chennai, south India, in 213 (84 female and 129 male) healthy, HIV-1/2 seronegative adults as volunteers. Whole blood specimens were processed for CD4+, CD8+ T-lymphocyte estimation and haematological parameters. The established range of CD4+ T-lymphocyte counts for men and women were 383-1347 cells/microl (mean 865 and median 845 cells/microl) and 448-1593 cells/microl (mean 1021 and median 954 cells/microl), respectively. Women had significantly higher absolute CD4+ Tlymphocyte counts (P<0.001) and CD4+:CD8+ T-lymphocyte ratio as compared to men. The established normal range of CD4+ T-lymphocyte % was 21-59 (mean 40.2 and median 40.1). The influence of age was not observed in any of the parameters except CD4+/CD8+ T-lymphocyte ratio with the >45 yr age group. Further studies with greater sample size may be required to define the staging of HIV disease in relation to the normal CD4 T-lymphocyte count in the general population.

HIV-1 western blot assay: What determines an indeterminate status?

BACKGROUND: The Western blot assay is the gold standard for the detection of antibodies to human immunodeficiency virus type 1 (HIV-1). However, indeterminate Western blot reactivity to HIV-1 proteins may occur in individuals, who may not be infected with HIV. AIM: This retrospective study was aimed to determine the diagnostic value of the interpretation criteria in relation to commercial kits for HIV-1 diagnosis. METHODS AND MATERIALS: A total of 556 serum/plasma specimens collected from high-risk population attending our HIV clinic from 2000-2004 were tested by three different western blot kits: NEW LAV BLOT I (n=244), HIV BLOT 2.2; (n=112), Genetic Systems HIV-1 (n=237). And the results of western blot strips were analyzed using the various interpretation criteria: WHO/NACO, CDC/ ASTPHLD, ARC, FDA, CRSS and JHU. Some specimens were run on more than one kit. RT-PCR assay was performed on 5 specimens, which were indeterminate with LAV BLOT I. RESULTS: The discrepancy in LAV BLOT I positive results were between 157(64)-176(72), and indeterminate results were between 44(18) to 63(25). No such variations were observed in genetic systems. There are some HIV negative (by PCR) specimens were indeterminate in LAV BLOT I revealing the kit more sensitive and less effective for diagnostic purpose. CONCLUSION: The genetic systems kit is superior to other kits we analyzed and its results are concordant with HIV-1 PCR results. To report, the choice of western blot commercial kit is paramount important than the use of particular interpretation criteria for the diagnosis of HIV-1.

Serodiagnosis of syphilis in a community: An evaluatory study.

PURPOSE: To analyse the prevalence of syphilis in the apparently healthy population and to provide data for implementation of the joint STD/HIV control programme, a population based study was undertaken by using 'probability proportional to size' cluster survey method in three randomly chosen districts of Tamil Nadu, India namely Dindigul, Ramnad and Tanjore. METHODS: Blood samples were collected from adults (n=1873) aged 15-45 years, from the selected households enrolled in this study. The sera were tested parallelly by rapid plasma reagin (RPR) and Treponema pallidum haemagglutination (TPHA) tests. Reactive samples by RPR and/or TPHA were later analysed by fluorescent treponemal antibody absorption (FTA-ABS) test. RESULTS: The prevalence of syphilis in the community of Tamil Nadu as per RPR positivity was 2.7% (50/1873) as against 0.7% by TPHA (13/1873). FTA-ABS positivity was observed in only 12 out of 48 (25%) RPR/TPHA reactive samples tested. By taking the positivity by two of the three tests, the community prevalence of acute ongoing syphilis in Tamil Nadu was determined as 1.1% (20/1873). CONCLUSIONS: The results confirmed that no single serological test for syphilis can act as the marker of ongoing acute infection in an apparently healthy population. The study suggests that for specific diagnosis of ongoing syphilis, the FTA-ABS test may be performed along with RPR and TPHA.

Diagnosis of hepatitis C virus infection by ELISA, RIBA and RT-PCR: a comparative evaluation.

OBJECTIVES: To evaluate the efficacy of second-generation ELISA (ELISA-2), third-generation ELISA (ELISA-3) and third-generation recombinant immunoblot assay (RIBA 3.0) for detection of antibodies to hepatitis C virus (anti-HCV) in comparison with reverse transcriptase-polymerase chain reaction (RT-PCR) to detect HCV RNA for the diagnosis of hepatitis C. METHODS: Sera of 108 patients with chronic liver disease (CLD) were analyzed by ELISA-2, ELISA-3, RIBA 3.0 and RT-PCR in the first part of the study; in the second part, sera of 105 patients with non-chronic liver disease were evaluated with ELISA-3, RIBA 3.0 and RT-PCR. RESULTS: In the CLD group, anti-HCV was positive in 4.6%, 14.8% and 16.6% by ELISA-2, ELISA-3 and RIBA 3.0, respectively. Among these anti-HCV positive cases, HCV RNA was positive in 100%, 58.9% and 64%, respectively. ELISA-2 did not give false-positive results, but missed substantial number of anti-HCV positive cases (p < 0.001). In the second group, anti-HCV was positive in 76.3% by ELISA-3 and 68.6% by RIBA 3.0 (p:ns). HCV-RNA was positive in 88.7% of ELISA- and RIBA-positive cases; in 60% of ELISA-positive, RIBA-indeterminate cases; and in 46.4% of ELISA-negative, RIBA-negative cases. CONCLUSIONS: ELISA-2 is not a suitable assay for routine screening. ELISA-3 was at par with RIBA 3.0 and it can be recommended for routine screening for anti-HCV. RT-PCR for HCV is of value in detecting early viremic, anti-HCV negative cases; this may be of importance in the treatment of hepatitis C.