Criterion Validity of the Isometric Contraction Test for Diagnosis of Axis I DC/TMD Considering Specific Muscles

Background: To determine the validity of the Isometric Contraction Test (ICTest) for the DC/TMD in axis I regarding specificmuscles such as the masseter, temporalis and medial pterygoid muscles.Methods: Forty patients with a diagnosis of TMD axis I of muscle origin and forty healthy controls were evaluated with theICTest. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (LR+)and negative likelihood ratio (LR−) were determined concerning the DC/TMD on axis I of muscle type, individually assessingthe masseter, temporalis and medial pterygoid muscles.Results: The ICTest achieved a sensitivity ranging from 41% to 88.9% in masseter and temporalis muscles with lower values forthe medial pterygoid muscle and when referred myofascial pain subtype was analysed. Specificity remained stable in both sit-uations, the subtype of myalgia and the muscles studied, ranging from 93.4% to 98.7%. The LR values indicated high variabilitydepending on the muscle and type of pain, although LR+ and LR− were ≥ 7.08 and ≤ 0.76%, respectfully, in all cases.Conclusions: The ICTest is highly specific when studying the masseter, temporalis and pterygoid muscles, with the latest oneshowing the poorest results. Referred myofascial pain exhibits the lowest validity for all the muscles.