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.