Transcultural Adaptation and Validation of the Fonseca Anamnestic Index in a Spanish Population with Temporomandibular Disorders

Background: The Fonseca Anamnestic Index (FAI) offers a simple method to screen temporomandibular disorders (TMD). This study aimed to validate the Spanish version of the FAI in patients with TMD. Methods: The sample consisted of 125 subjects (66 TMD and 59 controls) aged over 18 years. Construct validity, internal consistency, test-retest reliability, concurrent validity and capacity to discriminate between TMD and healthy subjects were analyzed. Results: The Spanish version of the FAI showed a structure formed by three factors. Cronbach’s alpha was 0.826. The reliability of the items varied between substantial to almost perfect and was excellent for the total score (intraclass correlation coefficient = 0.937). The standard error of measurement (SEM) was 6.52, with a minimum detectable change (MDC) of 12.78. FAI score showed a significant correlation with headache, neck pain and vertigo measurements. A cut-off point >35 showed a sensitivity = 83.33% and a specificity = 77.97% in differentiating between healthy and TMD patients, with an area under the curve (AUC) = 0.865. Conclusions: The Spanish version of the FAI is a valid and reliable instrument for diagnosing people with TMD, with appropriate general clinimetric properties. Discrimination between patients with and without TMD is excellent.