Measurement of rapid changes in health outcomes in people with influenza symptoms

Clinical trials' outcomes assessment requires symptoms and health status tracking, particularly where symptoms come and go rapidly. We report indicators assessing health in people suffering influenza symptoms where changes occur daily. Thirty-six people with influenza symptoms completed self-report questionnaires daily for 8 days: including the Influenza Impact Wellbeing Scale (IIWS) probing health, sleep quality and ability to perform usual activities; and the Assessment of Quality of Life (AQoL), a health-related quality of life instrument. An 11-item checklist, the Influenza Symptom Severity (ISS) scale, assessed influenza symptoms severity. Psychometric properties of the IIWS and ISS are reported. Over the 8 days, ISS scores decreased by 75%, IIWS scores increased by 58% and AQoL scores improved by 10% (all p < 0.01). Influenza symptoms recorded by the ISS scale predicted 50% of the variation in the IIWS. All three instruments were sufficiently sensitive to track rapid health status changes and may be useful outcomes measures in clinical trials involving influenza patients. These are promising results that require confirmation in larger studies.