Psychometric Properties of the Persian Version of the Short Form of the McGill Pain Questionnaire in Orthodontic Patients

Aims: Orthodontic pain is the most common reason why patients request for ceasing treatment. This study was intended to assess the psychometric properties of the Persian version of the SF-MPQ (P-SF-MPQ) after a translation and back-translation process. Instrument Methods: The items of the questionnaire were translated from English to Persian by an orthodontist and retranslated to English by another orthodontist. To determine the face validity and content validity, a questionnaire was prepared. The reliability of the research tool was evaluated by Cronbach’s alpha and intraclass correlation coefficient. In order to assess the construct validity, 200 patients were asked to fill out the P-SF-MPQ. Findings: Two items of SF-MPQ were omitted from the final version according to their low CVR. The mean of the CVI, CVR, and Impact Coefficient was obtained as 0.798, 0.53, and 3.29, respectively. To evaluate internal consistency Cronbach’s alpha was calculated as 0.851. To evaluate the stability of the results The ICC for the whole questionnaire was 0.848, which was statistically significant (p 0.001). The KMO value was calculated as 0.90, which indicates the appropriate sample size for exploratory factor analysis (KMO 0.6). The value of Chi-square was calculated as 108.52 which indicates the desirability of the model (p 0.001). Factor analysis showed that items of the P-SF-MPQ can be organized into three factors: chronic pain, beating pain, and sharp pain. Conclusion: The results showed that the Persian version of the revised McGill Pain Scale in orthodontic patients is valid and can be used to evaluate orthodontic pain in Iranian patients.