Validation of the General Practice Physical Activity Questionnaire after severe COVID-19

Background Physical inactivity is a risk factor for severe COVID-19 and often worsens after hospitalisation. Clinicians need quick, accurate assessments to target interventions. We aimed to assess the validity of the General Practice Physical Activity Questionnaire (GPPAQ) in adults recovering one year after COVID-19 hospitalisation . Methods Post-hospitalisation for COVID-19, adults attended a one-year-visit and completed the GPPAQ Physical Activity Index (PAI-4 active), 14-day wrist-worn accelerometry (Moderate-Vigorous PA [MVPA]- active), and other health outcomes. Validity was examined via : (i) internal consistency (factor analysis); (ii) measurement invariance across sex, age, and ethnicity using differential item functioning (DIF); (iii) convergent validity (GPPAQ sensitivity/specificity versus accelerometry); and (iv) construct validity (correlations with health outcomes). Results 752 participants had GPPAQ and accelerometry (265 female, mean± sd age 60.9±11.6 years, MVPA 18.75 min·day −1 (IQR 7.55, 36.11), PAI-1 46.8%, PAI-2 15.6%, PAI-3 19.4%, PAI-4 18.2%. Factor analyses supported good internal consistency with two factors (daily activities, physical exercise). Confirmatory factor Index (CFI) showed excellent fit (CFI 0.965). DIF indicated moderate variability by sex and age. GPPAQ-PAI showed limited sensitivity (26.3%) for correctly classifying physically active individuals, but higher specificity (88.4%) for classifying physical inactivity, and weak-to-moderate correlations with health outcomes. Conclusions GPPAQ demonstrates internal consistency, with construct and convergent validity in adults 1-year post-COVID-19 hospitalisation. GPPAQ effectively identifies inactive individuals to support clinical care; however, its sensitivity suggests underestimation of activity relative to accelerometry. Future pathways should combine GPPAQ with device-based assessment to optimise evaluation of physical activity to guide pulmonary rehabilitation and targeted interventions.