Intrarater and Interrater Reliability of the Modified Thomas Test

Introduction: The modified Thomas Test (MTT) is a method of assessing flexibility of the iliopsoas, rectus femoris and tensor fascia Latae. The aim of this study is to identify the intra and inter-rater reliability of the pass/fail scoring for the Modified Thomas Test (MTT) using digital photographs.

Methods: Six raters varying between 1 and 13years of clinical experience were used to review digital photographs of 20 semi-professional rugby players performing the /MTT. Raters were asked to score each muscle of the MTT either with 0 (fail) or 1 (pass). Digital photographs were allocated in a randomized order. Each rater reviewed each photograph three times at two week intervals.

Results: Cronbach's alpha (Cα) revealed a mean result of high reliability for both iliopsoas (Cα = 0.95) and rectus femoris (Cα = 1.00) flexibility. TFL flexibility values ranged from 0.64 to 0.95, demonstrating some inconsistencies within some of the 6 raters. Fleiss kappa (Fк) revealed a high mean reliability result across the 3 testing sessions for both iliopsoas (Fк = 0.78) and rectus femoris (Fк = 0.80) flexibility, along with a moderate reliability mean result for TFL (Fк = 0.56).

Conclusion: High intra and inter rater reliability was found for iliopsoas and rectus femoris flexibility with those for TFL found to be moderately reliable.