PCT, a precursor to calcitonin, is typically produced in response to bacterial infections and has been linked to pneumonia severity.[24] Studies suggest that elevated PCT level correlates with bacteremic CAP in adult pneumonia and are associated with inflammatory markers in pediatric CAP.[25,26] Ratageri et al[27] found the sensitivity and specificity of PCT (>0.5 ng/mL) for pneumonia were 29.7% and 87.5%, respectively, emphasizing its role in identifying pleural effusion and severity. Here, CALCA is linked to susceptibility to pneumonia measurement.