We evaluated the accuracy of self-reported home-assessed and self-measured waist circumference in 101 men and eighty-three women aged 28–67 years. The main outcome measures were subjects' self-reported and self-measured waist circumference, and self-classification according to the previously defined waist action level 1 (940 mm in men, 800 mm in women) and action level 2 (1020 mm in men, 880 mm in women), and waist circumference measured by the investigator using the ‘Waist Watcher’ tape-measure, as the reference method. The mean errors (95% CI limits of agreement) for subjects' self-reported waist circumference (self-reported minus reference; mm) were −67 (95% CI −210, 77) in men and −43 (95% CI −211, 123) in women, and for self-measured waist circumference (mm) using the ‘Waist Watcher’ (self-measured minus reference) were −5 (95% CI −62, 52) in men and −4 (95% CI −50, 42) in women. The proportions of subjects classified into waist action level 1 or action level 2 by the investigator were used as the reference method. Self-reported waist circumference of men and women respectively would be classified correctly in different categories based on action level 1 with sensitivities of 58·3 and 78·7%, and specificities of 98·5 and 98·7%, and action level 2 with sensitivities of 38·3 and 48·9%, and specificities of 98·5 and 98·7%. Using the ‘Waist Watcher’ with different colour bands based on the action levels, male and female subjects respectively classified themselves into correct categories according to action level 1 with sensitivities of 100 and 98·7%, and specificities of 98·1 and 98·2%, and according to action level 2 with sensitivities of 98·1 and 100%, and specificities of 100% for both sexes. Only 2% of the sample misclassified themselves into the wrong categories according to waist circumference action levels. In conclusion, people tend to underestimate their waist circumference, but the ‘Waist Watcher’ tape-measure offers advantages over self-reported home-assessed measurement, and may be used as a screening tool for self-classifying the risk of ill health through intra-abdominal fat accumulation.
