Comparison of CBNAAT and conventional real time RT PCR for HIV 1 viral load testing.

PURPOSE: HIV viral load testing is now recommended for monitoring of anti-retroviral treatment failure in PLHIV. Xpert® HIV-1 Viral Load is a fully automated CB-NAAT. A reduced turnaround time leads to prompt clinical management. Hence the current study was undertaken to compare Xpert® HIV-1 Viral Load with the routinely used conventional real time RT PCR. METHODS: The study was conducted in the Department of Microbiology of a tertiary care medical college after ethics committee approval. 100 HIV positive samples were tested by both CB-NAAT and conventional real time RT PCR for HIV 1 viral load. Results were analyzed using Spearman's correlation co-efficient and Bland Altman plot for agreement. The number of samples with inter assay differences in viral loads exceeding 0.5 log copies/ml was also recorded. The sensitivity, specificity, PPV and NPV as well as the possible misclassification were calculated at the clinically significant value of 1000 copies/ml. RESULTS: 25 samples in each of the four groups with log 10 value of <3, 3 to <4, 4 to <5 and ≥5 respectively were included. The log difference between the groups varied from 0 to 1.54. CB-NAAT has shown a statistically significant correlation with conventional real time RT PCR by Spearman's rank correlation (R = 0.972) (P < 0.01) and acceptable level of agreement with Bland Altman plot. The sensitivity, specificity, PPV, NPV and diagnostic accuracy was 80%, 100%, 100%, 93.75% and 95% respectively. The overall concordance was 95% with an upward misclassification of 6.25% and downward misclassification of 0%. CONCLUSIONS: Point of care technology with sample in/answer out approach makes it an excellent choice especially in resource constrained and remote settings.

Hepatitis B Virus (HBV) Infection in Liver Disease Patients in Mumbai, India with Special Reference to Hepatitis B Surface Antigen (HBsAg) Mutant Detection.

OBJECTIVES: To determine the prevalence of Hepatitis B Surface antigen (HBsAg) in patients attending the Hepatology Out Patient Department (OPD) of a tertiary care hospital and to compare the routinely used HBsAg detection kit with the mutant detection kit to find out the presence of mutants in a given setting. MATERIALS AND METHODS: A cross-sectional study was carried out in adult patients with liver disease attending the Hepatology OPD, of a tertiary care hospital in Mumbai, India. Age, gender and clinical history of the patient were recorded. Blood specimen was tested for HBsAg (Microscreen(TM) ELISA, Span diagnostics, India) and HBsAg mutants (Hepanostika HBsAg Ultra(TM) ELISA, Biomerieux, France). The samples with discordant results between these two ELISAs were confirmed by Hepatitis B Virus (HBV) Deoxyribonucleic Acid (DNA) Polymerase Chain Reaction (PCR) (Cobas Taqman(TM), Roche Molecular Systems, USA). RESULTS: Seven hundred and eighteen patients were enrolled in the study. The mean age of patients in the study group was 41 years (range 17 to 69 years). Four hundred and ninety seven (69.22%) were males and remaining were females. The prevalence of HBsAg was found to be 17.4%. The positivity amongst the male population was 18.1% which was higher than the female population (15.8%). Of the 718 samples tested, 120 were positive for HBsAg by Microscreen(TM) ELISA and 132 were positive by Hepanostika HBsAg ultra(TM). Of the 12 discordant samples, HBV DNA was detected in five samples indicating 0.7% prevalence of mutants. CONCLUSION: Hepatitis B is prevalent in liver disease patients. The mutant detecting assay is recommended in set-ups where missing HBsAg in patients would have tremendous impact on the outcome such as in blood donors, organ or tissue donors and antenatal screening of mothers. It is also helpful in chronic liver disease patients where the routine HBsAg detection test is negative and the other causes of chronic liver disease have been ruled out. However, it is not recommended for use in routine diagnostic set-ups where high false positivity would lead to over-diagnosis of the condition.

Laboratory tests for malaria: a diagnostic conundrum?

OBJECTIVES: To detect malarial parasites using the peripheral blood smear (PBS) and to compare the PBS with the immunochromatographic antigen test (i.e. OptiMAL and polymerase chain reaction (PCR)). METHODS: Six ml of blood was collected from each of 170 patients clinically suspected of having malaria. These samples were used to perform PBS examination, the OptiMAL test and PCR by standard protocol. RESULTS: PBS examination found malarial parasites in 86 (50.6%) samples. In comparison, 71 (41.8%) samples were positive by OptiMAL test whereas PCR could detect malarial parasites in only 44 (25.9%) samples. All 84 (49.4%) samples which were negative by PBS were negative by both OptiMAL and PCR. The sensitivity and specificity were respectively 85.54% and 100% for OptiMAL and 51.12% and 100% for PCR. CONCLUSION; Depending on the tests' operational feasibility, and the availability of adequate trained personnel, equipment and laboratory management systems, and considering its sensitivity and cost-effectiveness, peripheral blood smear remains the test of choice for malaria, especially in endemic areas.

HIV-2 Infection: Where Are We Today?

CONTEXT: The choice of antiretroviral therapy for HIV-2 differs from that for HIV-1, underscoring the importance of differentiating between the two. AIMS: The current study was planned to find out the prevalence of HIV-2 infection at our center and to find out the utility of the current diagnostic algorithm in identifying the type of HIV infection. SETTING AND DESIGN: Retrospective analysis in a tertiary care teaching institute over a period of three years. MATERIALS AND METHODS: All patients diagnosed as HIV infected using NACO/WHO HIV testing strategy III were included in the study. They were classified as HIV-1 infected, HIV-2 infected and HIV-1 and HIV-2 co-infected based on their test results. For discordant samples, immunoblotting result from National Reference Laboratory was considered as final. STATISTICAL ANALYSIS USED: Comparison between HIV-1, HIV-2 and HIV-1+2 positive groups for age, gender, route of transmission was made using chi squared test. P value < 0.05 was considered as significant. RESULTS: Of the total of 66,708 patients tested, 5,238 (7.9%) were positive for HIV antibodies. 7.62%, 0.14%, 0.08% and 0.004% were HIV-1, HIV-2, HIV-1 and HIV-2 co-infected and HIV type indeterminate (HIV-1 Indeterminate, 2+) respectively. The current algorithm could not differentiate between the types of HIV infection (as HIV-1 or HIV-2) in 63 (1.2%) cases. CONCLUSION: In areas like the Indian subcontinent, where epidemic of both HIV-1 and HIV-2 infections are ongoing, it is important to modify the current diagnostic algorithms to diagnose and confirm HIV-2 infections.