Comparison of complement fixation and fluorescent immunoassay (FIAX) for measuring antibodies to cytomegalovirus and herpes simplex virus.

An automated fluorescent immunoassay system (FIAX) was compared with complement fixation (CF) for measuring antibodies to cytomegalovirus (CMV) and herpes simplex virus (HSV) in clinical specimens. Compared with CF the specificity of FIAX (ability to detect a negative titer) was 95% for CMV and 92% for HSV. The sensitivity of FIAX (ability to detect a positive titer) was 98% for CMV and 95% for HSV. When paired samples were tested for significant titer rises, the concordance of the two assays for CMV was 96% and for HSV 80%. The FIAX assay was found to be reproducible when sera were tested within the same laboratory and in two different laboratories. The assay is fast, simple to perform, and not affected by anticomplementary activity. It is seen as a useful alternative to CF testing in a clinical virology laboratory.

Quantitative fluorescent immunoassay for measurement of antibody to Dirofilaria immitis in dogs.

An automated fluorescent immunoassay technique (FIAX; International Diagnostic Technology, Santa Clara, Calif.) has been developed for the quantitation of circulating antibodies in dogs infected with Dirofilaria immitis. Two groups of sera, group I consisting of 77 samples and group II consisting of 126 samples, were obtained from experimentally infected microfilaremic dogs, known negative controls, and clinically diagnosed cases of occult dirofilariasis. Antibody against a partially purified trichloroacetic acid-soluble extract of a soluble somatic extract of D. immitis was measured by FIAX and by an enzyme-linked immunosorbent assay (ELISA). A standard curve was drawn from four samples with known FIAX titers and fluorescent signal unit values. The standard curve was used to determine titers of unknown samples. The correlation coefficients determined in the analysis of log10 ELISA and log10 FIAX values were r = 0.9057 and r = 0.8976 in groups I and II, respectively. Eighty-three percent of the titer values calculated by FIAX in group I were within one dilution, and 95% were within two dilutions, of those titers obtained by ELISA. In group II, 79 and 96% of the values obtained by FIAX were within one and two dilutions, respectively, of those obtained by ELISA. FIAX proved to be a reproducible and convenient assay for the measurement of serum antibody in dogs experimentally infected with Dirofilaria.