Comparative analysis of CRP as a biomarker of the inflammatory response intensity among common viral infections affecting the lungs: COVID-19 versus influenza A, influenza B and respiratory syncytial virus

Severe acute respiratory syndrome-corona virus 2 (SARS-CoV-2) is associated with significant morbidity and mortality. C-reactive protein (CRP) is a useful inflammatory biomarker for patients admitted with an infection. This study aimed to compare CRP level as an indicator of inflammation severity between SARS-CoV-2 and common respiratory viral infections. A cross-sectional study of all adult patients hospitalized in the internal medicine department, geriatric department, or internal intensive care unit between 02/2012 and 06/2021 with laboratory-confirmed respiratory viral infection was performed. SARS-CoV-2, influenza A, influenza B, and respiratory syncytial virus (RSV) were studied. Patients with laboratory-confirmed concurrent viral or bacterial infections were excluded. Patients with malignancy were also excluded. Age, gender, comorbidities, and CRP level upon admission were compared between groups. Univariate and multivariable analyses were applied. Among 1124 patients, 18.2% had SARS‑CoV‑2, 48.3% influenza A, 18.9% RSV, and 14.6% influenza B. SARS‑CoV‑2 patients were significantly younger (median 69.4 vs. ≥ 76 years) and had lower Charlson score (median 3 vs. ≥ 4 in other groups) compared to patients with other viral pathogens. After adjustment for patients' age, gender and comorbidities, SARS‑CoV‑2 patients had a higher probability (OR = 1.84-2.02, p < 0.01) of having CRP values in the upper quartile (> 117 mg/L) compared to all other viral pathogens while between all others there was no significant difference. To conclude, a higher CRP level upon admission is approximately twice more common among SARS-CoV-2 patients compared to other widespread respiratory viruses which may demonstrate the higher intensity of inflammation caused by SARS-CoV-2.