Background: Arthritis could be caused by different etiologies ranging from rheumatologic diseases to infectious conditions. Therefore, early diagnosis of etiology and treatment is important. The purpose of this study was to determine the the M. pneumonia in synovial fluid of children with arthritis by 2 methods (serology and qualitative PCR).Methods & Materials: This trial was carried out as a cross sectional study in pediatric and orthopedic ward of Rasoul-e Akram hospital in Tehran, Iran. Seventy three patients (39 boys and 34 girls) with mean age of 11± 3.9 y/o were selected by continuous sampling after synovial fluid aspiration. All samples were evaluated by direct smear, culture and latex tests. Septic arthritis was diagnosed in 18 patients (25.4%). PCR and serology tests for M. pneumonia (specific IgM and IgG) were performed in 50 cases with negative culture. The results were compared by Independent T test. Results: According to physical examination and culture 18 patients (25.4%) were diagnosed with septic arthritis, 50 patients with non-septic arthritis were studied. Seventeen patients (33.3%) were IgG positive and 2 patients (4%) were IgM positive. Only 2 patients (4%) showed weakly positive results on PCR which did not demonstrate any association with serology. Conclusion: Positive PCR in SF (4%) definitely indicates active infection and M. pneumonia induced arthiritis. Although positive SF-IgM (4%) suggests either a current or a very recent M. pneumonia infection but not for SF-IgG (previous infection). So, we can summate that PCR, though being the best and most accurate method to detect M. pneumonia infection arthritis, is not considered a practical one due to costs and availability issues. Hence it can be safely replaced by serology test (Specific IgM) in SF for diagnosis of M. pneumonia arthritis, which is available in most of the hospitals and is much more economical as compared to PCR.
Keywords: Mycoplasma pneumonia, arthritis, specific anti body, PCR, SF-IgG, physical examination.