Development of a chronic pain-specific version of the Sickness Impact Profile

Given the prevalence and complexity of chronic pain, there is a need for measures of disability that (a) provide comprehensive, useful clinical information with regard to patient functioning, and (b) do so as briefly as possible to minimize respondent burden. The primary objective of this study was to reduce the length of a well-known, highly detailed measure of disability, the 136-item Sickness Impact Profile (SIP), and develop a psychometrically sound short form for use in chronic pain (SIP for Chronic Pain, SIP-CP).

A 2-parameter logistic item response theory model was used to develop the SIP-CP in a sample of adults presenting for treatment at an interdisciplinary rehabilitation program (N = 723). Items were assessed for inclusion at the subscale level; poorly contributing items were removed sequentially, and model fit was evaluated at each step until adequate fit was achieved. Finally, linear regressions examined the variance accounted for by the SIP-CP in relation to the full-length SIP in measures of patient functioning.

The SIP-CP contains 42 items that yield 7 subscale scores and 2 summary dimension scores, Physical and Psychosocial disability. Acceptable reliability and evidence of convergent and divergent validity were demonstrated for each component. The SIP-CP accounted for a similar amount of the variance in measures of depression, pain-related anxiety, pain acceptance, classes of prescribed analgesics, and pain-related medical visits as the full-length SIP.

The SIP-CP appears to provide robust clinical information with little loss of association with other key aspects of functioning, while substantially lowering response burden.