Reliability and Concurrent Validity of Shoulder Tissue Irritability Classification

Rating tissue irritability has been recommended to aid decision making in several recent clinical practice guidelines. An explicit method for rating tissue irritability was proposed as part of the Staged Algorithm for Rehabilitation Classification: Shoulder Disorders (STAR-Shoulder), but the reliability and validity of this classification are unknown. The purpose of this study was to examine the reliability and concurrent validity of shoulder tissue irritability ratings as part of a system designed to guide appropriate treatment strategy and intensity.

A clinical measurement, prospective repeated-measures cross-sectional design was used. The 101 consecutive participants with primary complaints of shoulder pain were assessed by pairs of blinded raters (24 raters in total) and rated for tissue irritability. Patients completed 3 patient-reported outcome (PRO) measures reflecting both pain and disability, and these scores were compared with ratings of tissue irritability. Paired ratings of irritability were analyzed for reliability with prevalence-adjusted, bias-adjusted Kappa for ordinal scales. Analysis of variance was used to compare PRO measures across different levels of irritability. Receiver operating characteristic curve analysis was utilized to derive cut-off scores for 3 PRO instruments.

Interrater reliability was 0.69 (95% CI = 0.59-0.78), with 67% agreement. All PRO measures were significantly different among 3 levels of tissue irritability.

There appears to be acceptable reliability and a strong relationship between PRO measures and therapist-rated tissue irritability, supporting the use of the STAR-Shoulder irritability rating system.

Several clinical practice guidelines have recommended that clinicians rate tissue irritability as part of their examination. This study provides important new information supporting the reliability and validity of the STAR-Shoulder tissue irritability rating system.