Biomarker MxA Differentiates Pediatric Viral and Bacterial Infections in Retrospective Study

In a retrospective diagnostic accuracy study evaluating 669 pediatric participants, whole-blood concentrations of myxovirus resistance protein A (MxA) were significantly higher in children with viral respiratory tract infections than in those with bacterial infections (P < 0.0001). MxA demonstrated the highest diagnostic accuracy among individual inflammatory biomarkers evaluated, yielding an area under the receiver operating characteristic curve (AUC) of 0.860, with a sensitivity of 73.12% and a specificity of 90.38%. In comparative testing, MxA outperformed conventional biomarkers including C-reactive protein (CRP, AUC 0.702), serum amyloid A (SAA, AUC 0.633), procalcitonin (PCT, AUC 0.610), and interleukin-6 (IL-6, AUC 0.546). However, MxA concentrations did not differ between isolated viral infections and viral-bacterial coinfections.

The investigation evaluated 414 children presenting with respiratory tract infections alongside 255 healthy controls, utilizing leftover EDTA whole-blood samples retrieved from routine clinical care. In healthy controls, concentrations of MxA—an interferon-inducible host-response biomarker—declined with age. Age-stratified receiver operating characteristic analyses were conducted to account for this physiological variation, revealing that diagnostic cutoffs varied substantially across age groups at 107.48 ng/mL, 82.34 ng/mL, and 42.33 ng/mL. Furthermore, age-stratified cutoffs did not uniformly improve specificity relative to the overall threshold.

To evaluate combined diagnostic strategies, multivariable logistic regression models were constructed. A combined model incorporating MxA, CRP, and age group achieved an apparent AUC of 0.931. Following internal validation using 2,000 bootstrap resamples, the model retained discrimination with an optimism-corrected AUC of 0.924. Additional internal validation assessments revealed an optimism-corrected Brier score of 0.0835, an optimism-corrected calibration intercept of -0.0099, and an optimism-corrected calibration slope of 0.9041.

Differentiating viral from bacterial respiratory tract infections in children remains a clinical challenge contributing to inappropriate antibiotic use. Although MxA discriminated isolated viral from bacterial infections in this cohort and the multivariable model retained discrimination after bootstrap adjustment, some model overfitting was observed. The researchers noted that prospective external validation and assessments of clinical utility are required before MxA-based strategies can be implemented in clinical care.

Subject of Research: Diagnostic performance of myxovirus resistance protein A in pediatric respiratory tract infections

Article Title: Age-stratified diagnostic performance of myxovirus resistance protein A for differentiating viral and bacterial respiratory tract infections in children: a diagnostic accuracy study

Article References: Ding, Y., Chen, Y., Chen, X., Zhong, R., Dai, J., Li, Y., Jiang, Z., Wang, H., & Li, S. (2026). Age-stratified diagnostic performance of myxovirus resistance protein A for differentiating viral and bacterial respiratory tract infections in children: a diagnostic accuracy study. BMC Infectious Diseases. https://doi.org/10.1186/s12879-026-14715-3

Image Credits: AI Generated

DOI: 10.1186/s12879-026-14715-3

Keywords: myxovirus resistance protein A, pediatric respiratory infections, diagnostic accuracy, biomarkers, C-reactive protein, viral infections, bacterial infections, retrospective study, Age-stratified, diagnostic, performance, myxovirus