ORIGINAL RESEARCH
Mark H. Ebell; Yewen Chen; Fangzhi Luo; Ye Shen; Samuel Coenen; Paul Little; Bruce Barrett; Daniel Merenstein; Margareta Leven
Corresponding Author: Mark H. Ebell MD, MS; Department of Family Medicine, College of Human Medicine, Michigan State University
Email: ebell.mark@gmail.com
DOI: 10.3122/jabfm.2024.240366R1
Keywords: Clinical Prediction Rule, Evidence-Based Medicine, Infectious Diseases, Influenza, Influenza Vaccines, Logistic Regression, Respiratory Diseases, Risk Score, Telehealth, Vaccination
Dates: Submitted: 10-07-2024; Revised: 01-24-2025; Accepted: 02-17-2025
Status: In production for ahead of print.
INTRODUCTION: To develop and externally validate a simple risk score for influenza diagnosis based using vaccination history and patient-reported symptoms.
METHODS: Adult outpatients in 12 European countries during flu season with a chief complaint of acute cough between 2007 and 2010 were used to derive and internally validate the risk score (GRACE data), and contemporary US data were used for external validation (EAST-PC data). Patient-reported symptoms were recorded and PCR was used to diagnose influenza. The score was derived using logistic regression and assigning points based on the beta-coefficients. The score was externally validated in a contemporary US population (EAST-PC data). Accuracy was measured using influenza prevalence in each risk group and the area under the receiver operating characteristic curve (AUC). Calibration was assessed by plotting observed versus expected.
RESULTS: We developed a risk score with 6 items (subjective fever, interfered with usual activity, headache, wheeze, phlegm, and recent flu vaccine) and a range from -5 to 6 points. The AUC was 0.75 for both derivation and internal validation subgroups. The prevalence of influenza was 15.1% in the GRACE data and 14.4% in the EAST-PC data. The percentage with influenza in the low, moderate and high-risk groups was 6.8%, 21.8%, 35.3 in the external validation population (EAST-PC data). The low-risk group included 61% of participants in the external validation. Calibration was excellent.
CONCLUSIONS: We developed and externally validated the FluScoreVax risk score, available as an app. It classifies 61% of patients as low risk, of whom only 7% had influenza.