An enzyme-linked immunosorbent assay (ELISA) was developed for the detection of measles immunoglobulin G antibody (MEASELISA). This assay was found to be comparable to the measles hemagglutination inhibition (HAI) test. Approximately 500 sera from three centers were tested by MEASELISA and the HAI test. MEASELISA demonstrated values of greater than 99% for sensitivity, specificity, and accuracy. Values were very precise, with a mean coefficient of variation of 5.4%. MEASELISA values were shown by linear regression analysis to increase as HAI titers increased. A coefficient of determination of 1.00 was obtained from test center three. MEASELISA values were found to be linearly related (r2 greater than 0.97) to MEASELISA titers, thus enabling quantitation of measles antibody from a single value. Also, data are presented that show MEASELISA to be equivalent to complement fixation for evaluating paired sera for the presence of a significant increase in antibody levels to measles virus.
A 1-h enzyme-linked immunosorbent assay (Rubestat) was developed for rubella virus immunoglobulin G detection. The assay used phenolphthalein monophosphate as the substrate, which, when developed, can easily be read visually. Rubestat compared very favorably to hemagglutination inhibition and commercial enzymelinked immunosorbent assays in its ability to determine immune status. Rubestat demonstrated >97% specificity, sensitivity, and accuracy as compared with other methodologies at 10 different laboratories. The Rubestat index values were precise, with coefficients of variation for intraand interassay variation of less than 10%. Mean index values had a linear correlation with hemagglutination inhibition titers (r2 > 0.97). A population distribution of index values illustrated two distinct bell-shaped curves representing the positive and negative populations. Studies of acute and convalescent serum pairs showed Rubestat to be as accurate as hemagglutination inhibition in determining seroconversion. * Corresponding author. 100 p.l of the substrate, phenolphthalein monophosphate in diethanolamine buffer (pH 9.8). (vii) After mixing for 15 min the reaction was stopped with 200 pL. of 0.1 N NaOH. The pink-colored reaction was read spectrophotometrically on a Dynatech reader at 550 nm. (viii) Assay controls included 1140
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