Agreement of Mechanical Diagnosis and Therapy Classification in People With Extremity Conditions

In the McKenzie system of mechanical diagnosis and therapy (MDT), a reliable system for the management of spinal problems, classifications are used to guide management strategies. For the classification of extremity disorders, interexaminer agreement has not been investigated with patients.

The study objective was to investigate interexaminer agreement for provisional MDT extremity classification with patients.

This was a reliability study with examiner masking.

A therapist with an MDT credential observed the assessments made by 2 therapists with MDT diplomas, who successively performed MDT assessments for 33 patients with extremity pain on the same day. Immediately after each evaluation, all 3 therapists assigned the most appropriate MDT classification from 15 categories; they were unaware of each other's selection. The observed agreement and the Cohen kappa were calculated for the MDT classifications.

The observed agreement for the 15 MDT categories of classification between the therapist with an MDT credential and the first therapist with an MDT diploma was 78.8%. The Cohen kappa was .72 (95% confidence interval=.54, .89), indicating good agreement. However, the observed agreement between the 2 therapists with MDT diplomas when the patient was assessed separately was 42.4%. The Cohen kappa was .21 (95% confidence interval=.01, .41), indicating poor agreement.

Study limitations included convenience sampling of patients, the small number of examiners, and the limited extremity experience of the therapists with MDT diplomas.

Interexaminer agreement for provisional MDT extremity classification was good when the examiners were seeing the same patient concurrently but poor when the patient was seen successively. Further studies are needed to establish which factors, including study method, are responsible for the divergent results of the MDT assessments of extremity disorders.