Validation of the Modified Helkimo Clinical Index for Diagnosing Temporomandibular Disorders in a Romanian Patient Sample

Background and objectives: Temporomandibular disorders (TMDs) encompass a heterogeneous group of conditions affecting the temporomandibular joint (TMJ), masticatory muscles, and associated structures. Although the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) currently represent the gold standard in clinical assessment, their complexity and time-consuming nature limit their applicability in routine dental practice. The modified Helkimo Index (mHI) has been proposed as a simplified alternative; however, its validation in specific populations remains insufficiently documented. Methods: This cross-sectional clinical validation study aimed to assess the diagnostic validity and reliability of the mHI in a Romanian patient cohort. 164 participants were enrolled, including 82 clinically diagnosed TMD patients and 82 age- and sex-matched controls. All participants were assessed using the mHI and the DC/TMD protocols. Pain perception was recorded using the Numeric Pain Rating Scale (NPRS). Statistical analyses included intraclass correlation coefficients (ICC), Pearson correlations, receiver operating characteristic (ROC) curve analysis, and generalized estimating equations (GEE-logit models) to determine diagnostic accuracy and inter-method agreement. Results: The modified Helkimo Index demonstrated excellent diagnostic performance, with a sensitivity of 86%, specificity of 84%, and an area under the ROC curve (AUC) of 0.89. A strong correlation was observed between mHI scores and DC/TMD diagnoses (r = 0.83, p < 0.001). Inter-examiner (ICC = 0.87) and intra-examiner (ICC = 0.91) reliability confirmed high reproducibility. Each additional point on the mHI score was associated with a 45% increase in the adjusted odds of a positive TMD diagnosis (OR = 1.45; 95% CI: 1.22–1.73). Application time for the mHI (5–10 minutes) was significantly shorter than that for the DC/TMD protocol (16–20 minutes). Conclusions: The modified Helkimo Index is a valid, reliable, and time-efficient alternative to the DC/TMD protocol for diagnosing TMDs, particularly in clinical settings with limited resources. Its favorable psychometric properties support its integration into general dental practice and population-level screening programs. Further validation is recommended in more diverse age and sociodemographic cohorts.