McKenzie Lumbar Classification: Inter-Rater Agreement by Physical Therapists

The goal of this inter-rater chance-corrected agreement study was to examine the association between therapists’ level of formal pre-credential McKenzie post-graduate training and agreement on the following McKenzie classification variables for patients with low back pain (LBP): main McKenzie syndromes, presence of lateral shift, derangement reducibility, directional preference and centralization. Minimal level of McKenzie post graduate training needed to achieve acceptable agreement of McKenzie classification system is unknown. Raters (N = 47) completed multiple sets of 2 independent successive examinations at 3 different stages of McKenzie post-graduate training (levels Part A&B, Part C, and Part D). Agreement was assessed with kappa coefficients and associated 95% confidence intervals (CIs). A minimum kappa threshold of 0.60 was used as a pre-determined criterion for level of agreement acceptable for clinical use. Raters examined 1,662 patients (mean age = 51 ± 15, Min, Max: 18 to 91, 57% women). Data distributions were not even and were highly skewed for all classification variables. No training level studied had acceptable agreement for any McKenzie classification variable. Agreements for all levels of McKenzie post-graduate training were higher than expected by chance for most of the classification variables except Part A&B training level for judging lateral shift and centralization and Part D training level for judging reducibility. Agreement between training levels Part A&B, Part C, and Part D were similar with overlapping 95% CIs.

The study’s results suggest that level of inter-rater chance corrected agreement of McKenzie classification system was not acceptable for therapists at any level of formal McKenzie post graduate training. This finding raises concerns regarding the clinical utility of the McKenzie classification system at these training levels. More studies are necessary to assess agreement levels for therapists who receive additional training or experience at the McKenzie credentialed or diploma levels.