Construct Validity and Responsiveness of the Rapid Assessment of Physical Activity in Adults Living With HIV

Abstract

ObjectiveTo evaluate the construct validity and responsiveness of the Rapid Assessment of Physical Activity (RAPA) for measuring physical activity (PA) in adults living with HIV. DesignSecondary analysis of an interrupted time-series intervention study. SettingCommunity-based fitness facility in Toronto, Canada. ParticipantsSixty-seven adults (N=67) living with HIV (n=5 women; mean age, 51.8±11.6 years) with available baseline data to assess for construct validity of the RAPA, of which 50 (n=4 women; age, 53.2±11.4 years) had follow-up data to evaluate responsiveness. InterventionsTwo months of a community-based exercise intervention involving thrice weekly multicomponent exercises. Main Outcome MeasuresWe used a single-item PA questionnaire as a convergent outcome to the RAPA, while peak oxygen consumption, general health status, and number of concurrent health conditions were divergent outcomes. We tested 11 a priori hypotheses (6 construct validity, 5 responsiveness) using Spearman ρ, Wilcoxon signed-rank tests, Cohen's d, standardized effect size (SES), and standardized response mean (SRM). We considered acceptable construct validity and responsiveness if >75% of hypotheses were confirmed. ResultsAll of the hypotheses (100%) for construct validity were confirmed. The RAPA demonstrated moderate correlations with the single-item PA questionnaire (ρ=0.61), and negligible correlations with divergent outcome measures (ρ=0.08-0.21). Two of the 5 hypotheses (40.0%) for responsiveness were confirmed. RAPA scores were significantly greater after 2 months of training (P<.001) and demonstrated a small to moderate effect size (d=0.50, SES=0.47, SRM=0.48). There was a low correlation between change in RAPA scores and change in single-item PA questionnaire scores (ρ=0.48). ConclusionsThe RAPA demonstrated acceptable construct validity and poor responsiveness in adults living with HIV. Therefore, the RAPA can be used cross-sectionally but may be used in conjunction with other measures of PA for adults living with HIV.