Graded Chronic Pain Scale: Validation of 1-month reference frame version

Method: The Validation Project, which includes 521 TMD subjects for cross-sectional data and 74 subjects for test-retest data, provided the data. Standard psychometric approaches of internal reliability, stability, and convergent/discrminant validation were used for testing the 1-month version.  Comparisons were made between the 1-month and 6-month versions via reliability analysis for pain intensity, interference, and GCPS status. 

Result: 1-month version: Internal consistency for pain intensity and interference for the 1 month version showed excellent results (Cronbach’s alpha = 0.84 and 0.95, respectively) Temporal stability was high for CPI (Interclass correlation coefficient (ICC) = 0.92), interference (ICC = 0.85) and chronic pain grade (weighted kappa = 0.74). Convergent (correlation range 0.35 to 0.83) and discriminant (range 0.0 to 0.5) validity was consistent with expected values.  ICC or kappa between 1-month and 6-month versions were 0.74 (CPI), 0.64 (interference), and 0.28 (CPG grade).  1-month and 6-month versions:  Based on published data, internal consistency and temporal stability were similar for pain and interference; GCP class was less stable for the 1-month version. Convergent and discriminant validity exhibited similar patterns.

Conclusion: The 1-month GCPS exhibits acceptable reliability and validity and is comparable to the 6 –month version for all parameters except for Graded Chronic Pain Grade, which when classified over 1-month frame is not reliable compared to that yielded by the 6-month reference frame.  Sensitivity to change remains an important attribute requiring further research.