Sickness Impact Profile

Development

The authors of the SIP sought to create a behaviorally based measure of sickness-related dysfunction that could be used for evaluation, program planning, policy formation, and cost-effectiveness analysis. Development of the SIP began in 1972 with an effort to collect statements describing impairment in various aspects of functioning from patients, caregivers, healthy individuals, and healthcare professionals. Additional statements were gathered by literature review. A series of field [Page 1042]experiments were conducted to reduce the number of statements, group the items by category, and assign weighted values to each item for scoring purposes. All items were subjected to rigorous methodological evaluation to ensure adequate reliability and validity and sensitivity to change and to assess the comparability of alternative administration procedures. Efforts were made to ensure that individuals representing various levels of illness and all sociodemographic groups were included. The SIP can be self-administered or interviewer administered. It takes approximately 20 to 30 minutes to administer and 5 to 10 minutes to complete the scoring procedures. Scores range from 0 to 100 and are calculated by tallying the weighted values associated with each endorsed item, dividing by the total possible score, and multiplying by 100. The SIP is available for use in several languages/cultures, including British, Chicano-Spanish, Danish, Dutch, French, German, Italian, Norwegian, and Swedish.

The SIP68 was published in 1994 in an effort to overcome one of the major criticisms of the SIP, its length. Other short forms have been developed but are typically specific to a condition of interest (e.g., arthritis, back pain, stroke). Using principal components analysis, researchers determined which SIP items contributed most to respondents' scores. The 68 items that emerged from this analysis comprise six categories: somatic autonomy, mobility control, psychological autonomy and communication, social behavior, emotional stability, and mobility range. These categories can be collapsed into three dimensions: physical, psychological, and social. Scoring of the SIP68 differs from that of the SIP in that the items are not differentially weighted. Total, subscale, and dimension scores are calculated by summing the endorsed items. Total scores range from 0 to 68; ranges for subscale and dimension scores depend on the number of items per scale. Because of divergent scoring procedures, the two questionnaires cannot be directly compared.

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