In the same study, when a procalcitonin (PCT) cut-off value of 0.55 ng/mL was applied, it demonstrated a sensitivity of 91% and a specificity of 81% in identifying secondary bacterial infections; on the other hand, using a C-reactive protein (CRP) cut-off value of 172 mg/L resulted in a sensitivity of 81% and a specificity of 76%. Here, CRP is linked to bacterial infectious disease.