Adaptation and multicentre validation of a patient-centred outcome scale for people severely ill with COVID (IPOS-COV)

BACKGROUND: Patient-centred measures to capture symptoms and concerns have rarely been reported in severe COVID. We adapted and tested the measurement properties of the proxy version of the Integrated Palliative care Outcome Scale–IPOS-COV for severe COVID using psychometric approach. METHODS: We consulted experts and followed consensus-based standards for the selection of health status measurement instruments and United States Food and Drug Administration guidance for adaptation and analysis. Exploratory Factor Analysis and clinical perspective informed subscales. We tested the internal consistency reliability, calculated item total correlations, examined re-test reliability in stable patients, and also evaluated inter-rater reproducibility. We examined convergent and divergent validity of IPOS-COV with the Australia-modified Karnofsky Performance Scale and evaluated known-groups validity. Ability to detect change was examined. RESULTS: In the adaptation phase, 6 new items were added, 7 items were removed from the original measure. The recall period was revised to be the last 12–24 h to capture fast deterioration in COVID. General format and response options of the original Integrated Palliative care Outcome Scale were preserved. Data from 572 patients with COVID from across England and Wales seen by palliative care services were included. Four subscales were supported by the 4-factor solution explaining 53.5% of total variance. Breathlessness-Agitation and Gastro-intestinal subscales demonstrated good reliability with high to moderate (a = 0.70 and a = 0.67) internal consistency, and item–total correlations (0.62–0.21). All except the Flu subscale discriminated well between patients with differing disease severity. Inter-rater reliability was fair with ICC of 0.40 (0.3–0.5, 95% CI, n = 324). Correlations between the subscales and AKPS as predicted were weak (r = 0.13–0.26) but significant (p < 0.01). Breathlessness-Agitation and Drowsiness-Delirium subscales demonstrated good divergent validity. Patients with low oxygen saturation had higher mean Breathlessness-Agitation scores (M = 5.3) than those with normal levels (M = 3.4), t = 6.4 (186), p < 0.001. Change in Drowsiness-Delirium subscale correctly classified patients who died. CONCLUSIONS: IPOS-COV is the first patient-centred measure adapted for severe COVID to support timely management. Future studies could further evaluate its responsiveness and clinical utility with clinimetric approaches. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12955-023-02102-4.