Craniofacial pain and disability inventory (CF-PDI): development and psychometric validation of a new questionnaire.
BACKGROUND
Orofacial pain, headaches, and neck pain are very common pain conditions in the general population and might be associated in their pathophysiology, although this is not yet clarified. The development and validation of a prediction inventory is important to minimize risks. Most recent questionnaires have not focused on pain, but pain is the common symptom in temporomandibular disorders, headaches, and neck pain. It is necessary to provide tools for these conditions.


OBJECTIVES
The purpose of this study is to present the development and analysis of the factorial structure and psychometric properties of a new self-administered questionnaire (Craniofacial Pain and Disability Inventory [CF-PDI]) designed to measure pain, disability, and functional status of the mandibular and craniofacial regions.


STUDY DESIGN
Multicenter, prospective, cross-sectional, descriptive survey design. A secondary analysis of the reliability of the measures was a longitudinal, observational study.


SETTING
A convenience sample was recruited from a hospital and 2 specialty clinics in Madrid, Spain.


METHODS
The study sample consisted of 192 heterogeneous chronic craniofacial pain patients. A sub-sample of 106 patients was asked to answer the questionnaire a second time, to assess the test-retest reliability. The development and validation of the CF-PDI were conducted using the standard methodology, which included item development, cognitive debriefing, and psychometric validation. The questionnaire was assessed for the following psychometric properties: internal consistency (Cronbach's α); floor and ceiling effects; test-retest reliability (Intraclass Correlation Coefficient [ICC]; Bland and Altman method); construct validity (exploratory factor analysis); responsiveness (standard error of measurement [SEM] and minimal detectable change [MDC]); and convergent validity (Pearson correlation coefficient), by comparing visual analog scale (VAS), the Tampa Scale for Kinesiophobia (TSK-11), the Pain Catastrophizing Scale (PCS), the Neck Disability Index (NDI), and the Headache Impact Test-6 (HIT-6). Multiple linear regression analysis was used to estimate the strength of the associations with theoretically similar constructs.


RESULTS
The final version of the CF-PDI consists of 21 items. Exploratory factor analysis revealed 2 factors ("pain and disability" and "jaw functional status"), both with an eigenvalue greater than one, explaining 44.77% of the variance. Floor or ceiling effects were not observed. High internal consistency of the CF-PDI (Cronbach's α: 0.88) and also of the 2 subscales (Cronbach's α: 0.80 - 0.86) was confirmed. ICC was found to be 0.90 (95% confidence interval [CI] 0.86 - 0.93), which was considered to be excellent test-retest reliability. The SEM and MDC were 2.4 and 7 points, respectively. The total CF-PDI score showed a moderate correlation with most of the assessed questionnaires (r = 0.36 - 0.52) and a strong correlation with the NDI (r = 0.65; P < 0.001). The NDI, VAS, and TSK-11 were predictors of CF-PDI.


LIMITATIONS
Only self-reported measures were considered for convergent validity. Future research should use physical tests to explore the clinical signs relating to pain and disability.


CONCLUSION
The CF-PDI showed good psychometric properties. Based on the findings of this study, the CF-PDI can be used in research and clinical practice for the assessment of patients with craniofacial pain.