Evaluation of Performance of Two Rapid Tests for Detection of HIV-1 and -2 in High- and Low-Prevalence Populations in Nigeria

Abstract

The availability of reliable human immunodeficiency virus types 1 and 2 (HIV-1/2) rapid tests in resource-limited settings represents an important advancement in the accurate diagnosis of HIV infection and presents opportunities for implementation of effective prevention and treatment interventions among vulnerable populations. A study of the potential target populations for future HIV vaccine studies examined the prevalence of HIV infections at six selected sites in Nigeria and evaluated the use of two rapid diagnostic tests (RDTs) for HIV. The populations included market workers at sites adjacent to military installations and workers at highway settlements (truck stops) who may have a heightened risk of HIV exposure. Samples from 3,187 individuals who provided informed consent were tested in parallel using the Determine (DT) and Stat-Pak (SP) RDTs; discordant results were subjected to the Uni-Gold (UG) RDT as a tiebreaker. The results were compared to those of a third-generation enzyme immunoassay screen with confirmation of repeat reactive samples by HIV-1 Western blotting. One participant was HIV-2 infected, yielding positive results on both RDTs. Using the laboratory algorithm as a gold standard, we calculated sensitivities of 98.5% (confidence interval [CI], 97.1 to 99.8%) for DT and 98.1% (CI, 96.7 to 99.6%) for SP and specificities of 98.7% (CI, 98.3 -99.1%) for DT and 99.8% (CI, 99.6 to 100%) for SP. Similar results were obtained when the sites were stratified into those of higher HIV prevalence (9.4% to 22.8%) versus those of lower prevalence (3.2% to 7.3%). A parallel two-test algorithm requiring both DT and SP to be positive resulted in the highest sensitivity (98.1%; CI, 96.7 to 99.6%) and specificity (99.97%; CI, 99.9 to 100%) relative to those for the reference laboratory algorithm.

FIG 1

Percent repeat reactivity by the Bio-Rad HIV-1/2 O EIA as confirmed by HIV-1 Western blotting or HIV-1 or HIV-2 RNA detection (gold standard) compared to Determine (DT) or Stat-Pak (SP) test results at sites 1 to 6 and at all sites combined.

FIG 2

Results of laboratory tests and RDTs for the higher and lower prevalence sites. Results of DT or SP independently or in combination are compared to those of the reference laboratory algorithm. Calculations of sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio of each test or in combination for correct classification of HIV infection are shown.

FIG 3

Number of false-positive and false-negative results, when DT and SP are used independently or in combination (DT-SP). False-positive samples are those not confirmed by HIV WB or RNA detection. False-negative samples are those that were EIA RR and confirmed as HIV positive by HIV-1 WB or RNA detection but misclassified by the RDT.