Development of the Physical Distancing Scale for COVID-19 Avoidance (PDS-C19©) in immunocompromised and non-immunocompromised individuals and its validation in the EAGLE Study.

BACKGROUND: Many immunocompromised individuals continue to practice physical distancing behaviors to avoid severe COVID-19 outcomes. To measure the intensity of these physical distancing behaviors, we aimed to develop and validate a standardized metric across age groups: the Physical Distancing Scale for COVID-19 Avoidance (PDS-C19©). METHODOLOGY: PDS-C19 development involved content scoping, initial draft PDS-C19 design phase, and exploratory testing (via asynchronous online forums). Psychometric properties (structural validity, reliability, and construct validity) of the PDS-C19 were evaluated using a random sample of immunocompromised and non-immunocompromised participants (n = 1059) of the EAGLE Study, including adults and children aged 0.5-17 years from the US and UK. Adult caregivers of children aged ≤ 12 years completed a proxy version of the PDS-C19 on their behalf, in addition to providing self-reported responses. RESULTS: Findings from the two asynchronous forums (n = 23 and n = 22) indicated that the items identified in the scoping phase were relevant and well-understood. As part of the structural validity analysis, item-response distributions, inter-item correlations, and exploratory factor analyses supported a nine-item unidimensional intensity scale. Confirmatory factor analyses reduced the PDS-C19 to seven items (two items were dropped due to high residual correlations or differential item functioning by age). Internal consistency was high (ω = 0.97); convergent validity was good, with high correlations (rmax=0.74) with clinical outcome assessments of the ability to participate in activities and with worry. The PDS-C19 had good known-groups validity, with scores distinguishable by types of activities, level of worry, and number of close contacts. CONCLUSION: The PDS-C19 had acceptable structural and construct validity and high internal consistency, demonstrating its value as a measure of physical distancing to avoid COVID-19 in immunocompromised and non-immunocompromised individuals.