title: Potential impact of different cytomegalovirus (CMV) IgM assays on an algorithm requiring IgM reactivity as a criterion for measuring CMV IgG avidity.
abstract: The measurement of cytomegalovirus (CMV) IgG avidity is a powerful tool for identifying individuals with recent CMV infection. Because such patients are expected to be positive for CMV IgM, several investigators have suggested that CMV IgG-positive sera first be screened for CMV IgM and then only the IgM-reactive sera be tested for avidity. We investigated the impact of different CMV IgM assays on such a reflexing algorithm using a panel of 369 consecutive IgG-positive serum samples submitted for avidity testing. A bead-based immunofluorescent assay (BIFA) identified 105 IgM-positive serum samples, whereas an IgM-capture enzyme immunoassay (EIA) identified 48 IgM-positive serum samples; this marked difference led us to evaluate additional CMV IgM assays. An enzyme-linked immunofluorescent assay (ELFA) and a chemiluminescent immunoassay (CIA) were used to test all sera with discordant BIFA/EIA results, all sera with concordant positive results, and selected sera with concordant negative results. The findings indicated that the ELFA would identify 74 CMV IgM-positive samples and the CIA would identify 64. Of the 23 low-avidity serum samples, 2 were IgM negative by BIFA, 3 by ELFA and CIA, and 4 by EIA; of the 23 intermediate-avidity serum samples, 6 were IgM negative by BIFA, 10 by ELFA, and 15 by EIA and CIA. In both these avidity groups, BIFA IgM-negative sera were also negative by the other 3 assays. These findings demonstrate that an algorithm requiring CMV IgM reactivity as a criterion for CMV IgG avidity testing does not identify all low-avidity sera and thus misses some cases of acute CMV infection.
authors.affiliation: Focus Diagnostics Reference Laboratory, Cypress, California, USA hprince@focusdx.com.
authors.forename: Harry E
authors.initials: HE
authors.lastname: Prince
authors.affiliation: Focus Diagnostics Reference Laboratory, Cypress, California, USA.
authors.forename: Mary
authors.initials: M
authors.lastname: Lapé-Nixon
authors.affiliation: Mayo Medical Laboratories, Jacksonville, Florida, USA.
authors.forename: Andrew
authors.initials: A
authors.lastname: Brenner
authors.affiliation: ARUP Laboratories, Salt Lake City, Utah, USA.
authors.forename: Nancy
authors.initials: N
authors.lastname: Pitstick
authors.affiliation: ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, Utah, USA Department of Pathology, University of Utah School of Medicine, Salt Lake City, Utah, USA.
authors.forename: Marc Roger
authors.initials: MR
authors.lastname: Couturier
mesh_terms: D000293:Adolescent; D000328:Adult; D000465:Algorithms; D000914:Antibodies, Viral / Q000097:blood; D000915:Antibody Affinity / Q000276:immunology*; D003587:Cytomegalovirus / Q000276:immunology; D003586:Cytomegalovirus Infections / Q000175:diagnosis* / Q000276:immunology*; D005260:Female; D005455:Fluorescent Antibody Technique / Q000379:methods; D006801:Humans; D007124:Immunoenzyme Techniques / Q000379:methods; D007074:Immunoglobulin G / Q000097:blood*; D007075:Immunoglobulin M / Q000097:blood*; D008163:Luminescent Measurements / Q000379:methods; D008297:Male; D008875:Middle Aged; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000175:diagnosis; D011933:Reagent Kits, Diagnostic; D055815:Young Adult
chemical_list: D000914:Antibodies, Viral; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D011933:Reagent Kits, Diagnostic