Validity and reliability of Youth Physical Activity Questionnaire (YPAQ) among Preadolescents and Adolescents in Low-Resource Communities in Karachi, Pakistan

Background : Physical activity (PA) during childhood is essential for healthy growth and development. Although objective devices provide accurate PA estimates, but are costly and resource-intensive, leading to reliance on subjective instruments. Such tools have not been validated among South Asian children and youth. The primary objectives of this study were to evaluate the criterion validity of the modified Youth Physical Activity Questionnaire (YPAQ) against accelerometer data considered as the gold standard for measuring moderate-to-vigorous physical activity (MVPA) and to assess test-retest reliability. Secondary objectives included identifying optimal YPAQ thresholds for MVPA based on Actigraph-derived data and examining gender differences in MVPA patterns within these communities. Methods : This cross-sectional validation study was conducted among school-going healthy children aged 9 to 14 years recruited from low-resource settings of Karachi. Participants’ physical or mental disabilities were excluded. Physical activity was objectively measured using Actigraph GT3X accelerometers worn for seven consecutive days. YPAQ was administered twice, one week apart. Criterion validity was evaluated using correlation coefficients (r), while test-retest reliability was assessed with intra-class correlation coefficients (ICCs) with corresponding 95% confidence intervals. Internal consistency was evaluated using Cronbach’s alpha. Receiver operating characteristic (ROC) curves were constructed to assess MVPA reported on the YPAQ in correspondence with Actigraph-derived measures. Results : Of the 252 enrolled children, 234 (93%) provided valid accelerometer data. The criterion validity coefficient for MVPA was modest [r = 0.37, (95% CI:0.29–0.44)]. Test-retest reliability was moderately strong [ICC = 0.73, (95% CI:0.68–0.77)], and internal consistency was good (Cronbach’s α = 0.75). The YPAQ demonstrated acceptable sensitivity, specificity, and area under the ROC curve in classifying per day of MVPA minutes. Gender-stratified analyses revealed weak criterion validity both for boys [r = 0.25, (95% CI:0.13–0.36)] and girls [r = 0.28, (95% CI:0.15–0.40)], while reliability estimates were comparable across genders. Conclusions : The modified YPAQ demonstrated modest validity and acceptable reliability in assessing MVPA among school-going children and youth in urban settings. These findings highlight the need for ongoing refinement and cultural adaptation of physical activity assessment tools to ensure accurate and contextually relevant estimates among South Asian children and youth, a population facing heightened risk of chronic diseases.