Updated on 22 August 2012
The sensitivity and specificity of the "do-it-yourself" or "home-based tests" for HIV are claimed to be 90 percent. It is evident that test kits detect 95-96 false positives for every 100 positive home HIV tests (estimated positive predictive value of 4.3 percent ). Studies based on screening of the US blood supply indicate that approximately 0.006 percent of the world population outside of the AIDS risk groups are predicted to carry HIV infection. If commercially available HIV rapid kits are 99.9 percent accurate (true-positive), then in a population of 100,000 individuals, 100 false positives (=100,000 x 0.1 percent ) for every six true positives. Of the 100,000 pregnant women or risk population screened, 500 will be HIV-infected (prevalence of 0.5 percent ), of which 495 will have positive screening tests (sensitivity of 99 percent ).
Out of every 100,000 individuals who are screened for HIV, there will be 995 false positive tests (specificity of 99 percent ). The very high percentage of false positive HIV antibody tests are due to cross reaction or non-specific binding of anti-carbohydrate antibodies, naturally occurring antibodies, passive immunization (receipt of gamma globulin or immune globulin) and other factors in blood.
We collaborated with Allen Healthcare Products (AHP), Malaysia, to strengthen HIV screening in Malaysia. AHP developed the 4th generation of Rapid HIV 1 & 2 Test, which is a single-use immunochromatographic assay for the detection of antibodies to HIV, type 1 and type 2 using whole blood, venous whole blood and serum or plasma.
Geneflux carried out clinical validation of AHP test kits using 184 sera specimen, further categorized into four groups, namely real time RT-PCR tested HIV positive sera (N=95 specimen), RT-PCR tested HIV negative sera, but positive for HIV antibody, under HAART (N=20), HIV negative sera (N=20) and HIV negative sera, tested positive for related sexually transmitted viruses (N=49). Four categories of HIV positive sera with different viral load were selected to bring variation to the clinical validation, namely less than 72IU/mL, viral load between 72-1000IR/mL, between 1000-10,000IU/mL and 10,000-100,000IU/mL.