HIV-antibody detection in children by competitive and direct micro-ELISA techniques.

ABSTRACT

A comparative study was carried out on 110 sera from children or infants, suspected of HIV-antibody presence following several micro-ELISA assays, using four direct micro-ELISA (Wellcozyme HIV 1 + 2, Rapid Elavia Mixt, Ortho Diagnostics, RECVIH) and a competitive system--Wellcozyme-Recombinant. In three of the four direct systems, as well as in the competitive system, significantly higher mean values of sample/cut off, and cut off/sample ratios, respectively, as compared to the direct systems RECVIH, were present. High optimal levels of sensitivity and specificity (%), as related to Western Blot results, were found with Wellcozyme direct and competitive kits, as well as with Rapid Elavia Mixt kit, as compared to lower levels exhibited by the other two direct system kits (Ortho Diagnostics an especially RECVIH). As regards three Western Blot undetermined results, obtained in patients with a severe clinical state and evolution to exitus, by comparing some serological markers of HIV infection in two serum samples belonging to the same case (second sample collected 4 weeks after collection of the first homologous sample), the disappearance of gag-encoded-p24 band in Western Blot, associated with negativation of HIV-p24-antibody and with the presence of free virus antigen in all three second serum samples occurred, that would reflect a probable fall of immune anti-HIV "barriers" during final stages of illness. Although Western Blot confirmation cannot be excluded, it seems to be useful to assay comparatively HIV-antibody presence by means of direct and competitive micro-ELISA systems, in the same serum sample.