Abstract: Objective　To explore relationship between nasopharyngeal Mycoplasma pneumoniae (MP) -DNA copies and clinical characteristics in Mycoplasma pneumoniae pneumonia (MPP) children. Method　A total of 294 hospitalized MPP children were enrolled retrospectively and grouped according to the levels of nasopharyngeal MP-DNA copies tested: low copy level group (≤103/mL, n=21), moderate copy level group (104-106/mL, n=156) and high copy level group (>106/mL, n=117). Clinical manifestations, laboratory results and image features of the three groups were compared. ROC curve was used to analyze the predictive value of MP-DNA copies in refractory Mycoplasma pneumoniae pneumonia (RMPP). Results　Compared with low and moderate MP-DNA copies groups, high MP-DNA copies group had longer duration of fever, higher peak temperature and CRP level. The incidence of consolidation or atelectasis, pleural effusion, multiple extrapulmonary complications and RMPP were significantly higher in high MP-DNA copies group than those in low/moderate groups. ROC curve analysis showed AUC of the MP-DNA copies for the diagnosis of RMPP was 0.701. The best threshold value estimated was 4.83×106/mL, the diagnostic sensitivity and specificity was 80.8% and 55.4%, respectively. Conclusions　There may be positive correlation between nasopharyngeal MP-DNA copies and inflammation, pulmonary and extrapulmonary damage in MPP children. High MP-DNA copies may serve as a clinical indicator for early diagnosis of RMPP.

Key words: Mycoplasma pneumoniae pneumonia;　MP-DNA copies;　nasopharyngeal;　child