Sex‐specific changes in vital signs and common blood tests on the day of influenza diagnosis

Abstract Early detection of influenza virus infection can reduce morbidity, mortality, and transmission by enabling earlier and more effective interventions. While influenza is primarily a localized respiratory infection, previous studies showed significant changes in pulse rate and temperature on the day of diagnosis. This study expands these findings to further identify diagnostic patterns by analyzing standard blood panels, including complete blood count, metabolic panels, coagulation panels, and C‐reactive protein. We evaluated 1896 influenza‐diagnosed patients using electronic health records, including demographics, vital signs, and blood test results within 60 days before and after diagnosis. We found significant differences in 14 of 19 blood tests on the day of diagnosis. Sex‐specific differences were notable: five tests showed changes in both sexes, while 10 differed by sex. Significant changes for females included increased levels of red blood cells, white blood cells, hemoglobin, glucose, aspartate aminotransferase (AST), and prothrombin time (PT), as well as decreased chloride levels. For males, significant changes included an increased estimated glomerular filtration rate (eGFR) and reduced levels of potassium and creatinine. These findings highlight the diagnostic potential of combining vital signs and blood test differences to distinguish influenza infection and emphasize the importance of considering sex‐specific variations in clinical assessments.