Objective: Using the common-sense model of illness behavior, we developed and validated a self-report instrument for assessment of patients' cognitive and emotional representations of diabetic peripheral neuropathy (DPN) influencing foot self-care.
Research design and methods: The Patient Interpretation of Neuropathy (PIN) questionnaire, generated from discussions with clinicians and interviews with patients with DPN, was administered to patients with DPN attending U.K. (n = 325) and U.S. (n = 170) diabetes centers. Psychometric tests of the PIN questionnaire comprised factor analysis, internal consistency, and test-retest reliability. Partial correlations and multivariate regressions established construct and criterion-related validity. The associations of PIN scales to past foot ulceration and foot self-care behaviors were compared with those using a generic measure of illness perception and emotion, the Revised Illness Perception Questionnaire (IPQ-R), which was adapted to neuropathy.
Results: Factor analysis of the PIN questionnaire produced 11 scales, which explained 69% of item variance. Nine factors measured patients' common-sense beliefs about DPN and their levels of understanding of DPN-related medical information. Two factors assessed the emotions of worry about potential consequences and anger at practitioners. Most scales demonstrated adequate internal (Cronbach's alpha = 0.62-0.90) and test-retest reliability (Pearson's r = 0.51-0.64). Partial correlations between the PIN and IPQ-R scales in corresponding domains were significant but modest (rp = 0.15-0.26). Finally, PIN scales showed significant associations with past foot ulceration and foot self-care behaviors, thereby confirming criterion validity.
Conclusions: The 39-item PIN questionnaire is a reliable and valid measure of patients' cognitive and emotional representations of neuropathy affecting foot self-care.