Utility of Assessing Cytokine Levels for the Differential Diagnosis of Pneumonia in a Pediatric Population*

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Although pneumonia is easily diagnosed, determining the causative agent is difficult due to low pathogen detection rates. We performed a prospective observational study to evaluate the utility of measuring inflammatory cytokine levels to discriminate between pneumonia caused by typical bacteria, respiratory syncytial virus, or Mycoplasma pneumoniae in a pediatric population.


Serum inflammatory cytokine levels at early stages of the disease were evaluated for pneumonia caused by the three different pathogenic microorganisms.


The Children’s Hospital of Zhejiang University School of Medicine, China.


One hundred sixty-six patients with bacterial pneumonia, 182 with M. pneumonia, and 167 with respiratory syncytial virus pneumonia.

Measurements and Main Results:

The levels of interleukin-6 for pneumonia were significantly higher with typical bacteria than with either Mycoplasma pneumoniae or respiratory syncytial virus (p < 0.001). The area under the curve for serum concentrations of interleukin-6 was 0.997. A serum interleukin-6 level of greater than or equal to 93.0 pg/mL had 100.0% sensitivity and 99.14% specificity in discriminating bacterial pneumonia from respiratory syncytial virus pneumonia and Mycoplasma pneumoniae pneumonia. The interleukin-6 levels were higher in patients with Mycoplasma pneumoniae pneumonia than in those with respiratory syncytial virus pneumonia (p < 0.001). They also simultaneously had lower interleukin-10 levels than patients with respiratory syncytial virus pneumonia who had interleukin-10 levels comparable to those of patients with bacterial pneumonia, indicating a significant difference in the interleukin-6/interleukin-10 ratio between patients with Mycoplasma pneumoniae pneumonia and respiratory syncytial virus pneumonia (median interleukin-6/interleukin-10 ratio, 2.5 vs 0.5; p < 0.001). At an optimal cut-off value of 0.8, the interleukin-6/interleukin-10 ratio showed 90.3% sensitivity and 88.0% specificity.


These results suggest that interleukin-6 is a good biomarker for identifying bacterial pneumonia and that the interleukin-6/interleukin-10 ratio is an effective biomarker for discriminating Mycoplasma pneumoniae pneumonia from respiratory syncytial virus pneumonia.

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