The filter paper is impregnated with anM. were positive by CF, and 15 (23%) were positive by ImmunoWELL-IgM. When both the acute- and convalescent-phase serum samples from each patient were examined, 61 (95%) of the 64 patients were positive by CF, 60 patients (94%) were positive by Remel EIA, 52 patients (81%) were IgM positive by the Meridian IC, and 29 patients (45%) were IgM positive by the ImmunoWELL-IgM assay. The Meridian IC was more sensitive than the other assessments for early detection of IgM antibodies. However, after examining paired serum samples, we concluded that the detection of IgM alone may not be useful for all cases of mycoplasma contamination, especially in an adult populace. Mycoplasma pneumoniaeis an important cause of upper and lower respiratory tract infections, including pharyngitis, tracheobronchitis, CDN1163 and pneumonia, in children and adults of all ages (3,12). Laboratory diagnosis ofM. pneumoniaeinfection has relied mainly on serologic assessments because the organism is usually hard to isolate (5,6,9,11,18). A reliable and sensitive serologic test for use in the early phase of contamination byM. pneumoniaeis needed to confirm the infection and to ensure CDN1163 that the appropriate antibiotic is used for treatment. The detection of specific immunoglobulin M (IgM) antibody, which appears 7 to 10 days after contamination and approximately 2 weeks before IgG antibody, has been shown to indicate a recent or current contamination withM. pneumoniae(10,1416). However, the presence of IgM in adult serum does Bmp7 not usually indicate a current contamination, because in some cases IgM has been shown to persist for up to a 12 months after contamination. In addition, the IgM response is usually either minimal or undetectable in some cases of adult reinfection withM. pneumoniae(5,10,16,19). Therefore, reliance around the detection of specific IgM alone, especially in an adult populace, could allow some infections to be missed. In a previous study (19), approximately 20% of adults did not mount an IgM response after contamination withM. pneumoniae. We tested CDN1163 paired serum specimens, obtained from 64 adult patients with probableM. pneumoniaerespiratory infections, with three commercial enzyme immunoassays (EIAs): the ImmunoCard (IC) mycoplasma EIA (Meridian Diagnostics, Cincinnati, CDN1163 Ohio), the Remel EIAM. pneumoniaeIgG-IgM antibody test system (Remel, Lenexa, Kans.), and the ImmunoWELL-IgM EIA (GenBio, San Diego, Calif.), now marketed through Alexon-Trend, Ramsey, Minn. The paired samples were also tested with a complement fixation (CF) assay, considered to be the serologic gold standard, to determine if a more timely diagnosis ofM. pneumoniaecould be obtained in the early phase of contamination. == MATERIALS AND METHODS == == Sera. == Acute- and convalescent-phase sera were obtained from 64 patients during suspected outbreaks of respiratory infections caused byM. pneumoniae(4,13). Most of the patients had chest X rays with infiltrates compatible with atypical pneumonia. Other features of the infections included cough, fever, and myalgias. Sera were held at 20C before being tested by the Meridian IC, ImmunoWELL-IgM, Remel EIA, and CF assessments. Twenty-one paired serum samples from an outbreak of respiratory illness due to parainfluenza virus were also tested with each of the assays. None of the serum samples were linked to individual patient identifiers. == Meridian IC. == The Meridian IC mycoplasma EIA is usually a qualitative procedure for the detection of IgM antibodies toM. pneumoniaein human serum. The test was performed according to the manufacturer’s instructions. Briefly, the test system consists of a plastic card with four openings that provide access to absorbent filter paper. The filter paper is usually impregnated with anM. pneumoniaeantigen extract in the top right port (test well). The top left port (control well) contains a human IgM reagent impregnated onto the paper. A patient’s serum was added to both lower wells (sample ports) and allowed to migrate to the upper (control and test) wells. Next, an anti-human IgM-alkaline phosphatase conjugate was added to both sample ports and allowed to migrate to the upper ports for 2 min. The upper ports were then.