Revisiting reliability of quantified perineal ultrasound: Bland and Altman analysis of a new protocol for the rectangular coordinate method

Abstract

Aims This study tested the reliability of a new protocol for the rectangular coordinate method of quantifying perineal ultrasound. Methods Representative scans of healthy primiparous females were quantified by positioning a pubic bone template, drawn onto an acetate sheet containing x–y axes, over scans, by aligning the x-axis with the pubic bone central axis. Values for x (D x ) and y (D y ) located the urethrovesical junction (UVJ) at Rest, and at maximal Valsalva and Kegel. Range of motion (V–K) was calculated. Bland and Altman analysis, correlations, and t -tests determined intra- and inter-rater reliability, and variance due to designation of the pubic bone central axis (template control). Results Correlations averaged 0.72, 0.70, and 0.92 for intra-rater, inter-rater, and template control experiments. D x Rest, D x Kegel, and V–K were reliable in all experiments. First and second measures for inter-rater D y Rest and D y Kegel, and template control D y Valsalva were significantly different. Bland and Altman analysis showed D y Rest, D y Kegel, and D x and D y Valsalva for both reliability experiments to have limits of agreement (LOA's) large enough to explain ≥50% of the actual value ranges. Template control LOA's explained ≤30% of the actual value ranges. Conclusions The reliability of this protocol varied according to the conditions analyzed; accurate reliability assessment of all conditions required Bland and Altman analysis; and the designation of the pubic bone central axis remained a source of variance between investigators. Our results suggest Bland and Altman analysis be used with each study that quantifies perineal ultrasound. Neurourol. Urodynam. 25:731–738, 2006. © 2006 Wiley-Liss, Inc.