Objective: To estimate the reliability of skinfold and girth measurements, and ratios involving these measurements, commonly used in epidemiological and clinical studies as measures of body fat distribution.
Design: Repeated measurements of body fat distribution measures were scheduled on randomly selected participants at the baseline clinical examination of the ARIC Cohort Study, by the same or by different technicians.
Setting: Probability sample of 45-65 year old residents selected from four US communities.
Measurements: Subscapular and triceps skinfolds were taken twice using a Lange caliper on standardized right-side locations. Waist and hip girths were measured using an anthropometric tape applied at the level of umbilicus and of the maximal protrusion of the gluteal muscles, respectively. Repeated measurements were taken 1-2 h apart.
Results: Inter-technician measurements of triceps skinfolds, subscapular skinfolds, waist girth, hip girth, and waist/hip ratio each had high reliability (R > 0.91). The reliability coefficient for triceps/subscapular ratio (R = 0.81) was somewhat lower. For skinfold measures, intra-observer coefficient of variations are lower than the ones observed in previous studies, and inter-technician coefficient of variations are comparable.
Conclusions: These results confirm previous findings which indicate that the reliability of girth measurements is greater than for skinfold measurements. As a consequence, the waist to hip ratio is less affected by measurement error than the skinfold ratio. Moreover, the expected gain in reliability from using the average of two skinfold measures, taken in succession, was not realized, indicating that when measurements are taken in rapid succession by the same technician, statistical independence between measures is questionable.