Validity of a two-item physical activity questionnaire for assessing attainment of physical activity guidelines in youth

Background: As physical activity is important for health and well-being, it is essential to monitor population prevalence of physical activity. Surveillance is dependent on the use of valid and reliable measurement tools. The PACE+ questionnaire is used globally in youth and has acceptable reliability; however it has not been validated in a European sample. The purpose of this study is to validate this instrument in a sample of 10-18 year old Irish youth. Methods: Participants (n = 419, 45.7 % male) completed the PACE+ two-item questionnaire and were asked to wear an Actigraph accelerometer for eight consecutive days. Freedson cut-points were used to estimate moderate to vigorous physical activity from accelerometer counts. Analyses compared self-report and accelerometry data in participants with (1) = 5 and (2) seven valid accelerometer days. Calculations were performed for the whole sample, and were stratified by sex and school level (primary; post-primary). Results: Spearman correlations between self-reported physical activity levels and accelerometry derived minutes of moderate-to-vigorous physical activity per day were small (r = 0.27; seven valid days) to moderate (r = 0.34; >= 5 valid days). Higher correlations were found in older participants (post-primary r = 0.39; primary r = 0.24) and females (r = 0.39; males r = 0.27) using = 5 valid days. The agreement level was high (68-96 %). The accuracy of classifying those not meeting the guidelines (specificity) was moderate to high (59-100 %). Conclusions: The PACE+ self-report instrument has acceptable validity for assessing non-achievement of the adolescent physical activity recommendations. The validity is higher in females and increases with age. The continued use of the tool is recommended and will allow for comparability between studies, tracking of physical activity over time including trends in youth population prevalence.