The diagnostic value of pressure algometry in myofascial pain of the jaw muscles.

Recent evidence suggests that evaluation of muscle tenderness in temporomandibular disorders (TMDs) patients might be improved by the use of pressure algometry; nevertheless, the evaluation of the diagnostic value of this tool has received little attention. The aim of this study was to assess the diagnostic value of pressure algometry in myofascial pain of the jaw muscles, by calculation of sensitivity (Se), specificity (Sp) and positive predictive values (PPV). Pressure pain thresholds (PPTs) of masseter and anterior temporalis muscles were assessed in 40 female myogenous TMD patients and 40 age-matched female controls. PPTs were significantly lower (P<0.001) in TMD patients than in control subjects for both masseter and temporalis muscles, being 40-50\% of the control values. Setting a cutoff value 1 s.d. below the mean PPT values of control subject, sensitivity and specificity were 0.67 and 0.85, respectively, for the masseter muscle and 0.77 and 0.87, respectively, for the temporalis muscle. When taking into account the prevalences of myofascial pain in the general population and in TMD clinics, the PPV ranged from 0.5 to 0.7. As a result of the low PPV, pressure algometry has strong limitations when used as a solitary diagnostic tool.