Psychometric Evaluation of the Krogh-Poulsen Test for the Diagnosis of the Temporomandibular Disorders

The Krogh-Poulsen Test is a classic instrument to measure dysfunction of the stomatognathic system whose psychometric properties are unknown. This study aimed to evaluate the psychometric properties of the Krogh-Poulsen Test for the diagnosis of temporomandibular disorders (TMDs). A cross-sectional study was designed, including 119 patients (63 patients with TMD and 56 healthy controls). Factorial validity, inter-rater reliability, error of measurement, diagnostic validity of the Krogh-Poulsen Test, and concurrent validity were analyzed. The Krogh-Poulsen Test showed a three-factor structure. The inter-rater agreement could be considered very good with a kappa index of 0.87 (95% CI 0.83-0.90) and Standard Error of Measurement of 0.79. Correlations were strong with other orofacial instruments, moderate with instruments measuring TMD-related disorders such as neck pain, headache, or dizziness, and poor with generic quality of life instruments. The Area Under the Curve ROC was 0.928 showing, for a cut-off point >1, a sensitivity of 90.48 (95% CI 80.4-96.4) and a specificity of 85.71 (95% CI 73.8-93.6) for the diagnosis of TMD disorders. The Krogh-Poulsen Test showed a three-factor structure, very good inter-rater reliability, a strong correlation with other orofacial instruments, and an excellent capacity to discriminate between patients with or without TMD.