Comparative analysis of routine peripheral blood parameters in influenza and COVID-19 patients: a retrospective study.

Authors

Mingquan Shang, Xin Ma, Qiang Xu, Hongmei Niu, Fuqian Zhao, Lei Wang, Daofu Shen

Published in

Revista do Instituto de Medicina Tropical de Sao Paulo. Volume 68. Pages e57. Epub Aug 21, 2026.

Abstract

Influenza and COVID-19 are major causes of respiratory illness, and differentiating between them remains a clinical challenge when molecular testing is unavailable. This retrospective study evaluated whether routine peripheral blood parameters could aid in this differentiation. Data from 848 participants (225 influenza, 358 COVID-19, and 265 healthy controls) were analyzed. Among all tested parameters, only white blood cell (WBC) count and age differed significantly between influenza and COVID-19 patients (median WBC: 8.45 versus 6.67×109/L, p<0.001; median age: 67 versus 71 years, p<0.001). Notably, procalcitonin (PCT) levels did not differ significantly between the two groups (p>0.05). The composite index WBC/Age amplified intergroup differences more effectively than other composite indices, including WBC×PCT, which produced a weaker effect. Receiver operating characteristic analysis revealed poor discrimination for all parameters and models: WBC count (AUC=0.67), age (AUC=0.59), WBC×PCT (AUC=0.60), and a logistic regression model combining WBC and age (AUC=0.67). Age-stratified analysis confirmed that WBC count remained significantly higher in influenza patients in both younger and older subgroups, but discriminatory performance was similarly limited (AUC=0.64 and 0.68, respectively). These findings indicate that, despite statistical differences in WBC count and age, routine blood parameters-whether alone or in combination-lack sufficient discriminatory power to reliably differentiate influenza from COVID-19 in this study. Molecular testing remains essential for accurate diagnosis.

PMID:
42659464
Bibliographic data and abstract were imported from PubMed on 28 Aug 2026.

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