clinical significance of real-time PCR for rapid diagnosis of mycoplasma pneumoniae in respiratory tract infection

ABSTRACT

Mycoplasma pneumoniae [M. pneumoniae] is a common cause of respiratory tract infections [RTIs]. Diagnosis of M. pneumoniae infection relies mainly on laboratory tests, as the clinical presentation is not significantly different from that seen with other pathogens causing RTI. Diagnosis has traditionally been obtained by serological diagnosis, but increasingly, molecular techniques have been applied. However, the number of studies actually comparing these assays is limited. The Real Time PCR [RT-PCR] assay for detection of M. pneumoniae was used and comparing with a conventional PCR assay, and with serology using IgM Immunofluorescence assay [IFA]. The study included 70 adult patients with manifestations of RTIs and 20 age matched healthy controls. All patients and controls subjected to the following thorough history and clinical examination, routine investigations as complete blood count [CBC], erythrocyte sedimentation rate [ESR], C-reactive protein [CRP], and chest-X-ray, blood samples were collected for serological testing [IgM-IFA]. nasopharyngeal swabs were done for PCR assays and for culture techniques. Diagnosis of M. pneumoniae was made on the basis of tbe conventional PCR results. The conventional PCR was positive for M. pneumoniae in 18 patients [25.7%] out of overall 70 patients and all the 18 patients positive by conventional PCR were also positive by RT-PCR. While, all controls were PCR negative by both techniques. The nasopharyngeal swab culture for M. pneumoniae was positive in 10[14.3%] out of 70 patients and negative in all 20 healthy controls. However, the M. pneumoniae IgM-IFA was positive for 21 [30%] out of 70 patients. So IgM IFA was positive in 3 patients with negative PCR, However, one case was positive for IgM- IFA among healthy controls. Comparing to conventional PCR, the RT-PCR gives 100% sensitivity, 100% specificity and 100% accuracy for diagnosis of M. pneumoniae, followed by IgM- IFA that give a sensitivity of 100%, specificity of 94.2% and accuracy of 95.7%, and the culture of M. pneumoniae gives 55.6% for sensitivity, 100% for specificity and 88.5% for diagnostic accuracy. The comparison of clinical data of patients diagnosed with M. pneumoniae infection [+ve PCR] and those who were M. pneumoniae negative [-ye PCR] revealed that no significant difference was reported as regard age or disease duration between the two groups of patients, while rhinitis was significantly more prevalent in the Mycoplasma-negative patients [p<0.01]. No significant difference was seen between the two groups regarding headache, malaise, sore throat, vomiting, fever, wheeze, or chest radiographic infiltrate [p>0.05]. Also, WBC counts, CRP levels and ESR values were significantly increased in PCR positive group as comparing to PCR negative group [p<0.05]. The molecular methods are superior for diagnosis of M. pneumoniae regarding accuracy, and providing more rapid diagnosis. In addition, using Real-Time PCR assay involves less hands, short time for diagnosis and meanwhile, rapid treatment and monitoring therapy