Is there a wastage of resources due to non-specificity of anti-HIV ELISAs?

Summary. A library of anti-HIV ELISA ‘grey-area’ and repeatably reactive samples sent for confirmatory testing, were retested using a second technique, the modified (Fujirebio Gelatin Particle) agglutination test (MAT). On testing 224 grey-area reactive samples, only four were found to be reactive with this second test. On retesting a further 259 ELISA repeatably reactive samples, of which only 33 were confirmed to be anti-HIV-1, only 45 were reactive by MAT; these included the 33 confirmed as positive samples, thereby reducing the false-positives from 226 to 12. The introduction of this second technique supported our decision to cease the referral of grey-area samples. It also demonstrated the high prevalence of non-specificity of repeatable reactivity associated with some of the most specific ELISA kits currently available.