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

To determine the validity of the Isometric Contraction Test (ICTest) for the DC/TMD in axis I regarding specific muscles such as the masseter, temporalis and medial pterygoid muscles.

Forty patients with a diagnosis of TMD axis I of muscle origin and forty healthy controls were evaluated with the ICTest. 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 assessing the masseter, temporalis and medial pterygoid muscles.

The ICTest achieved a sensitivity ranging from 41% to 88.9% in masseter and temporalis muscles with lower values for the medial pterygoid muscle and when referred myofascial pain subtype was analysed. Specificity remained stable in both situations, the subtype of myalgia and the muscles studied, ranging from 93.4% to 98.7%. The LR values indicated high variability depending on the muscle and type of pain, although LR+ and LR- were ≥ 7.08 and ≤ 0.76%, respectfully, in all cases.

The ICTest is highly specific when studying the masseter, temporalis and pterygoid muscles, with the latest one showing the poorest results. Referred myofascial pain exhibits the lowest validity for all the muscles.