A reliable and valid measure of COVID-19 patient-reported symptoms in outpatients: the Symptoms Evolution of COVID-19 (SE-C19) instrument
Background: There is no valid and reliable patient self-reported measure assessing symptomology among outpatients with COVID-19. The Symptoms Evolution of COVID-19 (SE-C19) is a self-administered new instrument that includes 23 symptoms, each rated for severity at their worst moment within the last 24 hours. We studied the psychometric properties of SE-C19. Methods: Reliability, validity, and sensitivity to change of the SE-C19 were assessed in 657 outpatients with confirmed COVID-19 enrolled in NCT04425629. SE-C19 and Patient Global Impression of Severity (PGIS) were administered daily from baseline (predose at Day 1) to end of study (Day 29). Findings: Most patients (70.0%) were aged ≤50 years and white (85.5%). At baseline, patients reported an average (SD) of 6.6 (3.9) symptoms (ie, rated as at least Mild) with 3.8 (3.3) of these symptoms being rated as Moderate or Severe. By Day 29, most symptoms had resolved; 74.4% of patients reported no symptoms and on average, only 0.6 (SD 1.5) were reported as at least Mild. Stable patients according to the PGIS showed scores with intraclass correlation values indicating moderate-to-good test-retest reliability (ie, 0.50-0.90). At baseline, 20 item scores (87%) varied significantly across PGIS defined groups supporting the validity of SE-C19. A symptom resolution endpoint was defined after excluding the item 'Sneezing', due to its low ability to discriminate severity levels, and 'Confusion', 'Rash', and 'Vomiting', due to their low prevalence in this population. Symptoms resolution required complete absence of all remaining items, except 'Cough', 'Fatigue', and 'Headache', which could be Mild or Moderate in severity. Interpretation: We identified 19 items that are valid and reliable to measure disease-related symptoms in COVID-19 outpatients and propose a definition of symptom resolution that could be used in future clinical trials and potentially, also in clinical practice.