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

OBJECTIVE: To evaluate the construct validity and responsiveness of the Rapid Assessment of Physical Activity (RAPA) for measuring physical activity (PA) in adults living with HIV. DESIGN: Secondary analysis of an interrupted time-series intervention study. SETTING: Community-based fitness facility in Toronto, Canada. PARTICIPANTS: Sixty-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. INTERVENTIONS: Two months of a community-based exercise intervention involving thrice weekly multicomponent exercises. MAIN OUTCOME MEASURES: We 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. RESULTS: All 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). CONCLUSIONS: The 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.