Validity of the Exercise Vital Sign Tool to Assess Physical Activity

Introduction: Assessment and counseling by healthcare providers can successfully increase physical activity; however, a valid instrument to effectively measure physical activity is needed. This study examines the validity of the Exercise Vital Sign tool by comparing Exercise Vital Sign data collected at Kaiser Permanente Northwest with accelerometry data.

Methods: Participants (n=521) completed accelerometer monitoring and had ≥1 Exercise Vital Sign measurement in their electronic medical record. Using accelerometry as the gold standard, the association between moderate-to-vigorous physical activity minutes per week estimated through Exercise Vital Sign and that estimated through accelerometry was examined using the Spearman correlation coefficient. Comparability of moderate-to-vigorous physical activity categories (inactive, lowly active, moderately active, sufficiently active) was assessed using simple and weighted κ statistics. Sensitivity, specificity, and positive and negative predictive values were calculated. The study was conducted in 2012-2015, with analysis in 2019-2020.

Results: Average accelerometry-based moderate-to-vigorous physical activity was 212 minutes per week, and 57% of the participants were considered sufficiently active. Exercise Vital Sign‒based moderate-to-vigorous physical activity averaged 170 minutes per week, and 53% of the participants were active. There was a positive correlation between the moderate-to-vigorous physical activity minutes per week reported through Exercise Vital Sign and that reported through accelerometry (r =0.38, p<0.0001). A fair agreement was observed between Exercise Vital Sign‒ and accelerometry-based moderate-to-vigorous physical activity categories (weighted κ=0.29), with the highest agreement occurring for those with physical activity level ≥150 minutes per week. The positive correlation increased when moderate-to-vigorous physical activity was examined dichotomously (<150 or ≥150 minutes per week, κ=0.34). The sensitivity, specificity, positive predictive value, and negative predictive value for Exercise Vital Sign (when compared with those of accelerometry) were 67%, 68%, 61%, and 73%, respectively.

Conclusions: The Exercise Vital Sign is a useful physical activity assessment tool that correctly identifies the majority of adults who do and do not meet physical activity guidelines.