Cost-effectiveness of nucleic acid amplification tests for identifying acute HIV infections

Pooled testing: A tool to increase efficiency of infant HIV diagnosis and virological monitoring

Background

Pooled testing, or pooling, has been used for decades to efficiently diagnose relatively rare conditions, such as infection in blood donors. Programmes for the prevention of mother-to-child transmission of HIV and for antiretroviral therapy (ART) are being rolled out in much of Africa and are largely successful. This increases the need for early infant diagnosis (EID) of HIV using qualitative nucleic acid testing and for virological monitoring of patients on ART using viral load testing. While numbers of patients needing testing are increasing, infant HIV infections and ART failures are becoming rarer, opening an opportunity for pooled testing approaches.

Aim

This review highlights the need for universal EID and viral load coverage as well as the challenges faced. We introduce the concept of pooled testing and highlight some important considerations before giving an overview of studies exploring pooled testing for EID and virological monitoring.

Results

For ART monitoring, pooling has been shown to be accurate and efficient; for EID it has not been tried although modelling shows it to be promising. The final part attempts to place pooling into the context of current mother-to-child transmission of HIV and ART programmes and their expected trajectories over the next years.

Conclusion

Several points warrant consideration: pre-selection to exclude samples with an elevated pre-test probability of positivity from pooled testing, the use of dried blood or plasma spots, and choosing a pooling strategy that is both practically feasible and economical. Finally, novel ideas are suggested to make pooling even more attractive.

NAT positivity in seronegative voluntary blood donors from western India

BACKGROUND AND OBJECTIVES

Prevalence and composition of Hepatitis B, Hepatitis C and HIV-1, NAT positive but seronegative voluntary blood donors from western part of India is yet to be documented.

MATERIAL AND METHODS

Over last 2 1/₂ years all the seronegative voluntary blood donors were tested using 10 minipools on a semiautomated NAT testing platform. The positively tested donors were followed up for at least five months for development of seropositivity.

RESULTS

79532 seronegative donations were tested by 10 minipool (MP) NAT leading to 51 positive sample (44 Hep B, 5 HIV 1 and Hep C positive). All the HIV and Hep C NAT positive donors eventually developed seropositivity and out of 44 Hep B NAT positive donors, 31 developed seropositivity within six months of follow up, following counseling of the donors. This data translate into NAT yield of 1:1559 donors for all virus taken together. NAT yield for Hep B 1:1807 donors were much higher than HIV 1 in 1:15906 and HCV yield of 1:39761. Semiautomated minipool NAT testing system was found to be cost effective way for improving blood safety.

INTERPRETATION AND CONCLUSION

Seronegative NAT yield in voluntary blood donors are quiet high in western part of India and in line with rest of the country is mainly due to Hepatitis B infection. Implementation of strict donor screening, Hep B vaccination of the population and sample mutation of NAT testing should be under taken on war footing.

Enhanced Sensitivity for Detection of HIV-1 p24 Antigen by a Novel Nuclease-Linked Fluorescence Oligonucleotide Assay

The relatively high detection limit of the Enzyme-linked immunosorbent assay (ELISA) prevents its application for detection of low concentrations of antigens. To increase the sensitivity for detection of HIV-1 p24 antigen, we developed a highly sensitive nuclease-linked fluorescence oligonucleotide assay (NLFOA). Two major improvements were incorporated in NLFOA to amplify antibody-antigen interaction signals and reduce the signal/noise ratio; a large number of nuclease molecules coupled to the gold nanoparticle/streptavidin complex and fluorescent signals generated from fluorescent-labeled oligonucleotides by the nuclease. The detection limit of p24 by NLFOA was 1 pg/mL, which was 10-fold more sensitive than the conventional ELISA (10 pg/mL). The specificity was 100% and the coefficient of variation (CV) was 7.8% at low p24 concentration (1.5 pg/mL) with various concentrations of spiked p24 in HIV-1 negative sera. Thus, NLFOA is highly sensitive, specific, reproducible and user-friendly. The more sensitive detection of low p24 concentrations in HIV-1-infected individuals by NLFOA could allow detection of HIV-1 infections that are missed by the conventional ELISA at the window period during acute infection to further reduce the risk for HIV-1 infection due to the undetected HIV-1 in the blood products. Moreover, NLFOA can be easily applied to more sensitive detection of other antigens.