title: Comparison of the fluorescent treponemal antibody absorption (FTA-ABS) test with the FTA-ABS double staining test for detection of antitreponemal immunoglobulin M in the 19S fraction of human serum.
abstract: A widely used immunoglobulin M (IgM) detection assay for the diagnosis of neonatal congenital syphilis is the fluorescent treponemal antibody absorption test used with fractionated serum (FTA-ABS 19S IgM test). Reading the results of the FTA-ABS test is more cumbersome than reading those of the FTA-ABS double staining (FTA-ABS-DS) test, a confirmatory test for specific IgG. To verify that the FTA-ABS-DS test used with an anti-human IgM conjugate could detect specific IgM in fractionated serum samples (FTA-ABS-DS 19S IgM test), 164 fractionated (QUIK-SEP IgM Isolation System; ISOLAB, Inc., Akron, Ohio) serum specimens from infected neonates or adults or from IgG-seronegative subjects were tested by both techniques. The sensitivity limits of the two tests were assessed with reactive serum samples diluted to an endpoint titer. Samples nonreactive by the FTA-ABS 19S IgM test (n = 74) were either nonreactive (n = 65), minimally reactive (n = 5), or reactive (n = 4) by the FTA-ABS-DS 19S IgM test. Samples minimally reactive by the FTA-ABS 19S IgM test (n = 32) were minimally reactive (n = 1) or reactive (n = 31) by the double staining test. All samples reactive by the FTA-ABS 19S IgM test (n = 58) were also reactive by the FTA-ABS-DS 19S IgM test. There was a directly proportional linear relationship (r = 0.9794) between titers obtained by both tests. FTA-ABS-DS 19S IgM titers were constantly equal to or higher than FTA-ABS 19S IgM titers. Fluorescence intensity reading repeatability was 91.4% for the FTA-ABS-DS 19S IgM test and 81.7% for the FTA-ABS 19S IgM test (P = 0.015). Because the more easily read FTA-ABS-DS 19S IgM test is at least as sensitive as, if not more sensitive than, the FTA-ABS 19S IgM test, it is a good alternative to the latter test for the detection of specific IgM in human fractionated sera for those using fluorescence microscopes with incident light.
authors.affiliation: Laboratoire de Santé Publique du Québec, Ste-Anne-de-Bellevue, Canada.
authors.forename: G
authors.initials: G
authors.lastname: Ozanne
authors.forename: M A
authors.initials: MA
authors.lastname: d'Halewyn
authors.forename: S A
authors.initials: SA
authors.lastname: Larsen
mesh_terms: D000328:Adult; D016009:Chi-Square Distribution; D016508:Fluorescent Treponemal Antibody-Absorption Test / Q000379:methods*; D006801:Humans; D007075:Immunoglobulin M / Q000097:blood*; D007231:Infant, Newborn; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013194:Staining and Labeling / Q000379:methods; D013587:Syphilis / Q000175:diagnosis* / Q000276:immunology; D013590:Syphilis, Congenital / Q000175:diagnosis*; D014210:Treponema pallidum / Q000276:immunology
chemical_list: D007075:Immunoglobulin M