Improved Diagnostics Help to Identify Clinical Features and Biomarkers That Predict Mycoplasma pneumoniae Community-acquired Pneumonia in Children

Abstract

Background: There are no reliable signs or symptoms that differentiate Mycoplasma pneumoniae (Mp) infection in community-acquired pneumonia (CAP) from other etiologies. Additionally, current diagnostic tests do not reliably distinguish between Mp infection and carriage. We previously determined that the measurement of Mp-specific immunoglobulin M antibody-secreting cells (ASCs) by enzyme-linked immunospot assay allowed for differentiation between infection and carriage. Using this new diagnostic test, we aimed to identify clinical and laboratory features associated with Mp infection.

Methods: This is a prospective cohort study of children, 3-18 years of age, with CAP from 2016 to 2017. Clinical features and biomarkers were compared between Mp-positive and -negative groups by Mann-Whitney U test or Fisher exact test, as appropriate. Area under the receiver operating characteristic curve (AUC) differences and optimal thresholds were determined by using the DeLong test and Youden J statistic, respectively.

Results: Of 63 CAP patients, 29 were Mp-positive (46%). Mp positivity was statistically associated with older age (median, 8.6 vs 4.7 years), no underlying disease, family with respiratory symptoms, prior antibiotic treatment, prolonged prodromal respiratory symptoms and fever, and extrapulmonary (skin) manifestations. Lower levels of C-reactive protein, white blood cell count, absolute neutrophil count, and procalcitonin (PCT), specifically PCT <0.25 μg/L, were statistically associated with Mp infection. A combination of age >5 years (AUC = 0.77), prodromal fever and respiratory symptoms >6 days (AUC = 0.79), and PCT <0.25 μg/L (AUC = 0.81) improved diagnostic performance (AUC = 0.90) (P = .05).

Conclusions: A combination of clinical features and biomarkers may aid physicians in identifying patients at high risk for Mp CAP.

Keywords: C-reactive protein; antibiotics; diagnosis; procalcitonin; treatment.

Figure 1.

Biomarker test results of Mycoplasma pneumoniae–positive community-acquired pneumonia (CAP) vs M. pneumoniae–negative CAP in children: procalcitonin (A), C-reactive protein (B), white blood cell count (C), absolute neutrophil count (D). The P value is indicated in the graphs (Mann-Whitney U test). Abbreviations: ANC, absolute neutrophil count; CAP, community-acquired pneumonia; CRP, C-reactive protein; Mp, Mycoplasma pneumoniae; PCT, procalcitonin; WBC, white blood cell.

Figure 2.

Receiver operating characteristic (ROC) curve of sensitivity vs specificity for clinical features (A), biomarkers (B), and a combination of both (C). Area under the ROC curve (AUC) differences (DeLong test): A and B, No significant AUC differences. C, *P = .37 (age vs combination of clinical features); **P = .05 (combination of clinical features vs combination of clinical features plus procalcitonin). Abbreviations: ANC, absolute neutrophil count; CRP, C-reactive protein; PCT, procalcitonin; RTI, respiratory tract infection; WBC, white blood cell.