Development and Validation of the "Physical Functional Impact Index on Chronic Pain" (PFIICP): A Formative Model...

Area of Science:

• Pain research
• Health outcomes assessment
• Psychometrics

Background:

• Reliable and valid instruments are essential for assessing chronic pain and its impact on daily functioning in clinical and research settings.
• Existing scales often include emotional, cognitive, and social factors, necessitating a more objective measure focused on physical performance.
• The Physical Function Impact Index on Chronic Pain (PFIICP) was developed to address this need.

Purpose of the Study:

• To develop and validate the PFIICP, a novel 12-item questionnaire.
• To evaluate the physical functional impact of chronic pain objectively.
• To establish the psychometric properties of the PFIICP using a formative measurement model.

Main Methods:

• A formative measurement model was employed for scale development.
• Data collected from 285 patients at baseline and 58 at follow-up (3-6 months).
• Statistical analyses included Spearman's rho correlations, intraclass correlation coefficient (ICC), and Pearson correlations.

Main Results:

• All 12 items showed statistically significant correlations (p < 0.05), indicating unique contributions.
• The PFIICP demonstrated good test-retest reliability with an ICC of 0.788 (95% CI: 0.731 - 0.833).
• Strong convergent validity was confirmed through significant correlations with the Brief Pain Inventory (BPI; r = 0.739) and Pain Disability Index (PDI; r = 0.739).

Conclusions:

• The PFIICP is a reliable and valid tool for assessing the physical functional impact of chronic pain.
• The formative model approach provides an objective measure of pain's effect on physical performance.
• The PFIICP is a robust instrument for use in clinical and research settings.