Evaluation of false positivity and cross reactivity in the investigation of Human Immunodeficiency Virus (HIV) antibodies

This study evaluated the causes of false positive Human Immunodeficiency Virus test results (F+HIV), cross reactivity of HIV antibodies with other non HIV antibodies, and efficiency of the serial and parallel testing algorithms. 100 blood samples randomly collected from clients attending the Heart to Heart HIV counseling and testing unit of FMC Umuahia, were screened using the rapid ELISA and Enzyme Immuno Assay (EIA) tests. Discordant HIV results were screened for Anti Streptolycin O (ASO), Rheumatoid factor (RF) and Hepatitis B surface antigen (HBsAg). Of the 100 samples, 73 were negative to HIV antibodies, 11 positive, and 16 discordant results. EIA confirmed 8 of 16 discordant results negative, 5 indeterminate and 3 positive. F+ results were 33%, and false negatives were 4%. A marked percentage of samples exhibited cross reactivity with ASO (8;62%), HBsAg(3;23%), and RF (2;15%). An Odds Ratio (OR) of 33:0 (95% CI 13.8-26.2), showed that Determine rapid test kit is 33 times more likely to give a false positive HIV result than Unigold rapid test kit. The parallel algorithm showed better efficiency than the serial. This study showed that F+HIV test result is prevalent, and cross reactivity is the plausible cause of F+HIV test results.Keywords: Cross- reactivity, false positive, HIV, Umuahia