Accuracy of IgM antibody testing, FQ-PCR and culture in laboratory diagnosis of acute infection by Mycoplasma pneumoniae in adults and adolescents with community-acquired pneumonia

Background: Diagnosis of community-acquired pneumonia (CAP) caused by Mycoplasma pneumoniae in adults and adolescents is hampered by a lack of rapid and standardized tests for detection. Methods: CAP patients from 12 teaching hospitals were prospectively and consecutively recruited. Basic and clinical information, throat swabs and paired sera were collected. Mycoplasma pneumoniae was detected by IgG and IgM antibody tests, fluorescence quantitative polymerase chain reaction (FQ-PCR) and culture. A comparative study of the diagnostic values of three methods, including sensitivity, specificity, positive and negative predictive values and positive likelihood ratio (PLR) was conducted. A fourfold or greater increase of IgG antibody titers of paired sera was set as the diagnostic gold standard. Results: One hundred and twenty-five CAP patients (52.8% males, median age 47 years, range 14-85) were enrolled. Twenty-seven (21.6%) patients were diagnosed with acute Mycoplasma pneumoniae infections by the gold standard. Specificity values of all three methods were around 90%. An increasing trend of sensitivity, positive predictive value and PLR was found, with the lowest in IgM testing (7.4%, 28.6% and 1.45), intermediate in FQ-PCR (40.7%, 50% and 3.63), and highest in culture (55.6%, 75% and 10.9). Conclusions: In the defined group of patients, there was a good agreement between positive rate of MP cultivation of throat swabs and acute M. pneumoniae infection (PLR of 10.9). Since the sensitivity is low in all of the evaluated methods, the logical approach would be to incorporate PCR, culture and serological tests for optimum diagnosis of acute Mycoplasma pneumoniae infections in adults and adolescents.