Routine admission biomarkers for identifying co-infection and stratifying severity in pediatric macrolide-resistant...

Early identification of co-infection and timely risk stratification remain difficult in children with pneumonia caused by macrolide-resistant Mycoplasma pneumoniae (MRMP). This study aimed to investigate whether routinely available admission parameters were associated with bacterial and/or viral co-infection and severe disease in children with MRMP pneumonia.

This single-center retrospective cohort study included children with MRMP pneumonia admitted to The Sixth Affiliated Hospital of Harbin Medical University from August 1 to December 31, 2023. MRMP was confirmed by targeted next-generation sequencing (t-NGS) detection of M. pneumoniae with macrolide resistance-associated mutations. Patients were first classified as having MRMP mono-infection or MRMP co-infection with bacteria and/or viruses based on clinical, laboratory, imaging, and t-NGS findings. The co-infection group was then further divided into mild and severe subgroups according to disease severity. Demographic characteristics and admission laboratory parameters were compared between groups. Logistic regression and receiver operating characteristic (ROC) analyses were performed.

A total of 278 children with MRMP pneumonia were enrolled, including 78 with mono-infection and 200 with co-infection. In the first-stage analysis, platelet (PLT) levels on admission were higher in the co-infection group than in the mono-infection group [290.50 (243.00, 362.00) vs. 265.00 (220.50, 326.25)×10⁹/L, P=0.03]. However, no independent factor associated with co-infection was identified by multivariable analysis, and the discriminative performance of PLT was limited [area under the curve (AUC) =0.584]. Among the 200 co-infected patients, 159 were mild and 41 were severe. Compared with the mild group, the severe group had higher neutrophil percentage (NEUT%), D-dimer, lactate dehydrogenase (LDH), and procalcitonin (PCT) levels, but lower lymphocyte count (LYM) and albumin (ALB) levels on admission. Multivariable logistic regression showed that ALB was independently associated with lower odds of severe disease [odds ratio (OR) =0.800, 95% confidence interval (CI): 0.710-0.900, P<0.001], whereas PCT was independently associated with a higher odds (OR =9.440, 95% CI: 1.110-80.340, P=0.04). The combination of ALB and PCT yielded an AUC of 0.720 for identifying severe co-infection, compared with 0.704 for ALB alone and 0.704 for PCT alone.

In children with MRMP pneumonia, PLT showed limited discriminatory value for identifying bacterial and/or viral co-infection, whereas lower ALB and higher PCT on admission were associated with severe disease among co-infected children.