Interexaminer reliability of supine leg checks for discriminating leg-length inequality

The purpose of this study was to quantify interexaminer reliability of a standardized supine leg check procedure used to screen for leg-length inequality.

Two doctors of chiropractic used a standardized supine leg check procedure to examine 50 volunteers for leg-length inequality. The order of examination was randomized. The side and magnitude of leg-length inequality were determined to the nearest 1/8 in. Subjects and examiners were blinded. Interexaminer reliability was assessed with a Bland-Altman plot, tolerance table of absolute differences, a quadratic weighted κ statistic for quantitative scores, and a Gwet's first-order agreement coefficient for dichotomous ratings.

The quadratic weighted κ statistic to quantify the reliability of the rating scale was 0.44 (95% confidence interval, 0.21-0.67), indicating moderate reliability. The 2 examiners agreed exactly 32% of the time, within 1/8 in 58% of the time, within 3/16 in 72% of the time, and within 3/8 in 92% of the time. The Bland-Altman plot revealed possible heterogeneity in reliability that requires additional study. The examiners agreed on the presence of a leg-length inequality of at least 1/8 in in 40 (80%) of 50 subjects (first-order agreement coefficient, 0.76), suggesting good agreement for this diagnostic category.

The examiners showed moderate reliability in assessing leg-length inequality at 1/8-in increments and good reliability in determining the presence of a leg-length inequality.