Multicenter evaluation of a new commercial assay for detection of immunoglobulin M antibodies toToxoplasma gondii

Abstract

A new commercial assay for detection of IgM-specific antibodies to Toxoplasma gondii (IMx Toxo IgM, Abbott, USA), based on microparticle enzyme immunoassay technology, was evaluated at 15 clinical sites in Europe and the USA. Performance characteristics were established by testing clinical specimens collected randomly from pregnant women, blood donors, individuals with suspected Toxoplasma gondii infection and individuals confirmed HIV positive. Reference testing was performed using Toxo-M EIA (Abbott). Specimens evaluated at European sites yielding discordant results between the new assay and the reference EIA were further tested with an immunosorbent agglutination assay; at sites in the USA, discordant results were resolved using Platelia Toxo IgM (Sanofi, France) and Vidas Toxo IgM (bioMérieux, France) assays. In addition, matched plasma and serum, heat-treated and non-heat-treated specimens, and fresh and frozen specimens were evaluated at the USA sites. At European sites the new commercial assay had a sensitivity of 95.6% (196/205), a specificity of 99.8% (3,137/3,143) and an agreement of 99.6% (3,333/3,348) following resolution of discordant results; sensitivity in the USA was 97.4% (184/189), specificity was 99.8% (1,204/1,207) and agreement was 99.4% (1,388/1,396) following resolution. The new IMx Toxo IgM is a sensitive and specific assay for measurement of IgM antibodies to Toxoplasma gondii in human serum and plasma.

Evaluation of the second generation IMx Toxo IgG antibody assay for detection of antibodies toToxoplasma gondii in human sera

“…The false positivity of seven results was probably due to the laboratory policy of heating the HIV samples, and confirms the manufacturer's recommendation not to use IMx for heated samples. Similar discrepant results with heated sera were reported, to a lesser degree, by Luyasu et al (20) with IMx Toxo IgG when testing 546 sera from the United States, but not with European sera. In the USA sera, HIV-infected patient sera were included.…”

“…The 508 serum samples were collected over one month without selection in two hospitals 300 km apart (18,19) and not on the basis of the results obtained with another assay (13) or according to clinical status (5,(14)(15)(16)(17). All the tests were performed in the same laboratory, which avoids variations linked to center (20). The results of IgM Toxoplasma antibody detection are given here because detection is routinely combined with IgG Toxoplasma antibodies in France.…”

Performance Characteristics of Six IMMULITE 2000 TORCH Assays

“…The IMMULITE 2000 assay method run on the IMMULITE and the Access assay have been compared with the Platelia and Vidas assays in several previously published studies. [18][19][20][21][22] These studies have shown good concordance for these 4 assays in different pairings, although in most, there were discordant samples that required additional testing to resolve. The IMMULITE 2000 data compared with the consensus results showed much improved concordance with overall agreement of 96.1% vs 81.4%.…”

Study of Abbott Toxo IMx system for detection of immunoglobulin G and immunoglobulin M toxoplasma antibodies: value of confirmatory testing for diagnosis of acute toxoplasmosis

“…Luyasu et al recently evaluated the IgM IMx assay in a multicenter study (8). In their study, overall agreement between the IgM IMx and a capture IgM ELISA (Abbott Toxo IgM EIA) ranged from 99.4 to 99.6% (8).…”

“…Luyasu et al recently evaluated the IgM IMx assay in a multicenter study (8). In their study, overall agreement between the IgM IMx and a capture IgM ELISA (Abbott Toxo IgM EIA) ranged from 99.4 to 99.6% (8). The excellent agreement between the two tests for IgM antibodies may have been due to the large numbers of randomly tested samples from blood donors or pregnant women and a smaller number of serum samples from patients with suspected toxoplasmosis.…”