[Comparison of 2 ELFA methods for the automatized diagnosis of HIV infection]

Evaluate two recent tests for HIV infection diagnosis using the Enzyme-Linked Fluorescent Assay (ELFA) technique for rapid diagnosis in microbiology or virology laboratories.

A panel of 429 sera with different Ab prevalencies and different sources was prepared: 50 blood bank samples from habitual donors; 8 with positive results from other blood banks; 50 from individuals infected with HIV at various stages; 164 from subjects having practices of risk, with a prevalence of 24.4%; and 157 hospital samples selected at random, with a prevalence of 12.2%. All the samples were analyzed using IMX HIV-1/HIV-2 (ELFA A) and VIDAS HIV-1+2 (ELFA B) tests. Samples yielding positive results from either of the two tests were confirmed by WB. In the cases of indeterminate WB, p24 antigenemia was detected, the positive cases being confirmed by neutralization.

From the panel of sera studied, 112 samples were reactive by ELFA A and 109 by ELFA B. The concordance between both assays was 97.3% for reactive samples and 99.1% for non-reactive. WB confirmation showed a global sensitivity of 100% in both tests, with a specificity of 98.4% for ELFA A and 99.3% for ELFA B. Three samples positive for both tests but indeterminate for WB corresponded to sera in the seroconversion window period, one with positive p24 antigenemia.

The new ELFA technology is shown to be an adequate rapid, automatized diagnosis method which decreases risks from laboratory manipulation, with good sensitivity and specificity characteristics for the diagnosis of Ab HIV in health care settings.