Video instructions improve accuracy of self-measures of waist circumference compared with written instructions.

OBJECTIVE To determine whether video-based instructions improve the accuracy of self-measures of waist and hip circumference compared with written instructions. DESIGN Population-based, cross-sectional study. Self-measurements of waist circumference (WC) and hip circumference (HC) of fifty-seven participants randomly allocated to receive either written instruction or video instruction were compared with those of a trained technician. SETTING Aberdeen, Scotland, and Brussels, Belgium, between February and April 2010. SUBJECTS Adults aged 18-62 years with a high level of English language and no prior training in anthropometry. RESULTS WC was significantly overestimated by the written method (1·75 cm bias; P = 0·007) but not the video method (0·95 cm bias; P = 0·239). HC was significantly underestimated in both written (-0·35 cm bias; P = 0·009) and video methods (-0·75 cm bias; P = 0·046). Reliability was not significantly affected by age, sex, BMI or WC. Bland-Altman plots demonstrated wide limits of agreement for WC (-6·83, 6·08 cm for written method; -10·14, 6·72 cm for video method) and HC (-12·85, 1·60 cm for written method; -10·82, 2·50 cm for video method). CONCLUSIONS Video technology can support more accurate self-measurements of anthropometric data in epidemiological studies. Further research is warranted using larger and more heterogeneous samples in order that results can be generalised.