Analysis of Eight Commercial Enzyme Immunoassay Tests for Detection of Antibodies to Mycoplasma pneumoniae in Human Serum

Abstract

Mycoplasma pneumoniae is an important etiologic agent of primary atypical pneumonia in children and adults. The diagnosis of M. pneumoniae infection is commonly confirmed through serologic testing. In this study, we used paired sera from 51 patients (all with confirmed M. pneumoniae infection and positive complement fixation [CF] titers) to compare the results of eight enzyme immunoassays (EIAs) available commercially in the United States. We compared two single-use EIAs and six plate-type EIAs. Results from acute-phase sera ranged from only 7 (14%) positive by ImmunoWELL (GenBio) immunoglobulin M (IgM) EIA to 23 (45%) positive by Zeus IgG EIA. When both the acute-phase and convalescent-phase serum samples were examined, positive results ranged from 20 (39%) by the ImmunoWELL (GenBio) IgM assay to 45 (88%) positive by the Remel IgG-IgM EIA. In this study, the single-use EIAs by Remel and Meridian were more reliable than were the plate-type EIAs. Among the plate-type EIAs, the Zeus and DiaSorin assays (which detect antibodies to protein antigens) were more sensitive than the ImmunoWELL assay (which detects antibodies to glycolipid antigens). In general, IgG EIAs on convalescent-phase sera were more concordant with one another than were IgM EIAs with one another. Scatter plot analysis of convalescent-phase sera showed that, as the CF titer dropped, the IgM assays identified fewer positive convalescent-phase sera. In contrast, the IgG assays provided fairly consistent positive results for convalescent-phase sera with CF titers of 64 and above. Results of individual tests and overall limitations of serodiagnostics for M. pneumoniae infections are discussed.Mycoplasma pneumoniae is an important etiologic agent of tracheobronchitis and primary atypical pneumonia in children and adults. It is responsible for 20% or more of communityacquired pneumonias overall (8) and can also be a significant cause of severe pneumonia requiring hospitalization in the elderly (12). Because they lack a cell wall, mycoplasmas do not respond to penicillins and other beta-lactams commonly used for the treatment of bacterial pneumonia. Laboratory diagnosis of M. pneumoniae infection is usually established through serological or molecular testing because the organism grows slowly and is difficult to isolate from clinical specimens (10,11,17). A reliable and sensitive serologic test for use in the early stages of M. pneumoniae infection is needed to confirm the clinical diagnosis and to ensure that the appropriate antibiotic therapy is used (5, 7).The detection of specific immunoglobulin M (IgM) antibody, which appears 7 to 10 days after infection and approximately 2 weeks before IgG antibody, has been shown previously to indicate a recent or current infection with M. pneumoniae (13,14). However, specific IgM in adults does not always indicate an acute infection because it can persist for up to a year after infection with M. pneumoniae (2, 4). In addition, an IgM response may be either minimal or undetectable when adults are reinfected (9, 15)...

Comparison of Laboratory Diagnostic Procedures for Detection ofMycoplasma pneumoniaein Community Outbreaks

“…Many require collection of both acute-and convalescent-phase samples to identify a 4-fold increase in titer suggestive of an active infection [6]. Although serologic tests may provide important retrospective information, the impracticality of obtaining the followup sample limits their use when rapid confirmation of etiology is needed.…”

“…Complement fixation testing lacks sensitivity and specificity [5]. Commercially available serologic test kits for detection of antibodies to M. pneumoniae possess inherent limitations of specificity and sensitivity and, more importantly, depend on patient compliance with the timely acquisition of acute-and convalescent-phase serum samples for accurate interpretation [6]. Molecular-based assays, such as real-time PCR, have recently been shown to aid in the rapid identification of outbreaks of M. pneumoniae infection and provide greater sensitivity than do traditional methods [7][8][9][10].…”

Relevance of Serology for Mycoplasma Pneumoniae Infection Among Children with Persistent Cough

“…Several commercial tests utilizing passive agglutination, indirect immunofluorescence and immunoenzymatic assays are available and widely used for the detection of antibodies specific to M. pneumoniae in human sera. The complement fixation test, being as it is unspecific and insensitive, is no longer accepted [18]. However, several factors i.e.…”

“…In addition, IgM antibodies may not be present if the serum sample is obtained too early in the infection. Moreover, an IgM response may be either minimal or undetectable when adults are infected and during re-infection [16,18]. Thus, a negative result of IgM evaluation does not exclude current infection, especially in patients over the age of 45 years.…”

The role of Mycoplasma in upper respiratory infections

“…A recent study found that only 14 of 27 (52%) acute-phase sera tested positive by various IgM assays, but this number rose to 39 (88%) when convalescent sera were tested [ 30 ]. The percentage of persons with acute infection that demonstrate a positive IgG response in the acute phase was less than 50% in the same study, but when convalescent sera were tested, the IgG-positive specimens rose to 82% [ 30 ]. Thus, defi nitive diagnosis requires seroconversion in paired sera obtained 2 to 4 weeks apart and assayed at the same time.…”