Pain measurement in TMD patients: evaluation of precision and sensitivity of different scales.

The aim of this study was to evaluate the precision and sensitivity of four different pain rating scales in 59 temporomandibular disorders (TMD) patients. The capacity of describing changes in symptoms during treatment was also addressed. All patients were asked to answer four pain scales: Visual Analogue Scale (VAS), Numerical Scale (NS), Behaviour Rating Scale (BRS) and Verbal Scale (VS). Two measurements were taken before any treatment. After beginning it, follow-ups and repeated measurements were taken 1 week, 15 days, and every month for 6 months. Statistical analysis showed significant differences (P < 0.05) for all scales, but the NS (P > 0.05), when the two initial measurements were analysed. Regarding the sensitivity, all pain scales demonstrated general symptom improvement of 30-50%, when initial and final figures were compared (P < 0.01). Also, the most significant improvement occurred in the first 2 months after beginning the management programme. Authors concluded that the NS was more accurate to measure reproducibility of pain. As for the capacity of expressing changes during the treatment, all scales demonstrated symptom decrease of 30-50% in a period of 6 months. Caution when analysing the results is recommended because of the subjective aspect of pain measurement, the absence of a 'gold standard' for comparison and the natural fluctuation of TMD symptoms.