Clinical profiles of Mycoplasma pneumoniae pneumonia in children with different pleural effusion patterns: a retrospective study.

Background: The clinical significance of the presence or absence of Mycoplasma pneumoniae (MP) in pleural effusion in Mycoplasma pneumoniae pneumonia (MPP) children has not yet been elucidated. Herein, we investigated the clinical implication of pleural fluid MP positive in children with MPP.

Methods: A total of 165 MPP children with pleural effusion requiring thoracocentesis were enrolled in this study. They were subsequently divided into two groups according to the presence or absence of MP in pleural effusion, namely positive group (n = 38) and negative group (n = 127). Information on their clinical manifestations, laboratory findings, radiological characteristics and treatment modalities was retrospectively collected from medical chart reviews.

Results: The length of hospitalization (15.00 (10.75-19.25) vs. 11.00 (9.00-14.00) days, p=0.001) and total course of illness (23.00 (18.00-28.00) vs. 20.00 (17.00-24.00) days, p=0.010) were significantly longer in the positive group than in the negative group. The occurrence of pericardial effusion (23.7% vs. 7.9%, p=0.017), atelectasis (73.7% vs. 53.5%, p=0.027) and necrotizing pneumonia (23.7% vs. 7.9%, p=0.017) were more frequent in the positive group compared to the negative group. The levels of neutrophil percentages (82.35% (75.40%-85.78%) vs. 72.70% (64.30%-79.90%), p<0.001), C-reactive protein (CRP) (71.12 (37.75-139.41) vs. 31.15 (13.54-65.00) mg/L, p<0.001), procalcitonin (PCT) (0.65 (0.30-3.05) vs. 0.33 (0.17-1.13) ng/ml, p=0.005), serum lactate dehydrogenase (LDH) (799.00 (589.00-1081.50) vs. 673.00 (503.00-869.00) U/L, p=0.009), D-dimer (6.21 (3.37-16.11) vs. 3.32 (2.12-6.62) mg/L, p=0.001) on admission were significantly higher in the positive group than in the negative group. These pronounced differences significantly contributed to the identification of MPP with MP positive pleural effusion, as evidenced by the ROC curve analysis. Marked elevations in adenosine deaminase (49.25 (36.20-60.18) vs. 36.20 (28.10-46.50) U/L, p<0.001) and LDH levels (2298.50 (1259.75-3287.00) vs. 1199.00 (707.00-1761.00) U/L, p<0.001) were observed in pleural fluid of the positive group when compared to the negative group. Meanwhile, the number of patients on low molecular weight heparin (LMWH) therapy (9 (23.7%) vs. 12 (9.4%), p=0.028) was higher in the positive group. Multivariate logistic regression analysis revealed that D-dimer > 7.33 mg/L was significantly associated with the incidence of MP positive pleural effusion in MPP (OR=3.517).

Conclusions: The presence of MP in pleural fluid in MPP children with pleural effusion indicated a more serious clinical course. D-dimer > 7.33 mg/L was a related factor for MP positive pleural effusion in MPP. The results of the present study would help in the creation of a therapeutic plan and prediction of the clinical course of MPP in children.