Sickness Impact Profile (SIP): A Patient-Reported Outcome Measure

Original SIP version authors: Marilyn Bergner, Betty Gilson, and Ruth A. Bobbitt

Author
Laura Mitchell, PhD, Johns Hopkins University, Baltimore, USA

The Sickness Impact Profile (SIP) is one of the oldest and most systematically developed patient reported outcome measures. The SIP provides a sensitive, clinically valid questionnaire-based tool to assess sickness-related behavior dysfunction. It is still a frequently used generic quality-of-life measure. There is a recognized need to accurately determine whether healthcare practices are effective at improving an individual’s or treatment group’s ability to perform everyday activities. The SIP is broadly applicable across types and severities of illness, as well as across demographic and cultural subgroups. The SIP is designed to evaluate various kinds of patient dysfunction in many different areas of activity. The result is a complete assessment of patient activity dysfunction expressed as a percentage related to their illness.

A distinctive aspect of the SIP is that it is a self-report of activity limitation. The patient endorses statements that measure the activity that the patient is actually performing that day, rather than what they believe they could perform. Each query is written in easy-to-understand sentences in the first person and the present tense. The only response option is a Yes answer or a check mark to endorse Health , Health-related quality of life, Health Status Questionnaire each item that describes the person’s activity related to their health on that particular day.
The SIP includes questions in three dimensions: physical, psychosocial and other “Independent” domains. There are multiple categories within each dimension. The physical dimension includes questions relating to ambulation, mobility, body care and movement.

The psychosocial dimension includes queries related to social interaction, alertness and emotional behavior, and communication. Independent categories define patient ability to sleep and rest, eat, work, manage the home, and participate in recreation and pastimes.

The independent categories can be scored separately if desired. The overall SIP score includes all of the queries in the dimensions. Scoring is done using a numeric scale value by the number and type of queries answered. A total SIP score can be recorded for the entire tool, as well as scoring at the category level. Total SIP score is expressed as a percentage where 100% represents maximal dysfunction and 0% represents no dysfunction.2
The SIP instrument can be used to assess sickness-related dysfunction for not only individuals, but also groups of patients with specific diagnostic conditions. Over time, consistent profiles of dysfunction may emerge when patients with a specific diagnosis have similar SIP scores. Those profiles can be critical for developing healthcare strategies.

Background and Development of the Sickness Impact profile.

The SIP was one of the first assessments of overall health available and continues in use today. The development and revision of the SIP instrument has been described in detail.3 In brief, the SIP has been carefully optimized over time beginning with a lengthy prototype SIP in 1972, and refined after a 1973 pilot study and a 1974 field trial. Surveys and clinical tests of the SIP4-7 were done in 1976 to gauge reliability of types of administration: self-administration, interviewerdelivered administration and maildelivery administration. Results suggest that a trained interviewer assisting with a self-assessment is one of the better ways to obtain reliable and valid data. Clinical validation was performed as well as determination of the SIP descriptive validity.3 The sensitivity and validity results demonstrate the value of the SIP as a valuable measure of health status. The final, refined version of the SIP instrument contains 136 items and 12 categories. The SIP has been validated and in use for over 30 years in clinical trials, epidemiological studies, and program evaluations for a variety of conditions. The SIP is as relevant now as it was when it was developed. Published SIP scores are available for approximately 18 different disease conditions or population groups.8 These scores could be useful for comparison of the burdens of a particular illness relative to other conditions.

Advantages of the Sickness Impact Profile

It provides a measure of patient health status in a single numerical score which may be most desirable for some research studies and trials
It includes detailed instructions for the subject, as well as an administration manual with extensive instructions for an interviewer administering the SIP to ensure useful and accurate results.
It is relevant for assessing dysfunction in patients in a wide range of morbidity to evaluate care strategy.
It can be administered multiple times, and is sensitive enough to detect changes or differences in health status that occur over time or between groups.
It is useful for studies of poor health levels of a population, or to compare subgroups or population.
It is available translated and validated into Mexican-American Spanish9 and translated into more than 20 non-U.S. languages and dialects.

Overview of the instrument

Application: broad subject population, including patients with very low levels of health
Number of items (questions): 136
Number of categories: 12
Age range: any with sickness related behavior dysfunction
Mode of completion: self completion or by interviewer
Scoring results: numeric, expressed as a percentage of dysfunction

References

Garratt A, Schmidt L, Mackintosh A, et al. Quality of life measurement: bibliographic study of patient assessed health outcome measures. British Medical Journal 2002;324:1417
Damiano AM. The Sickness Impact Profile™ User’s Manual and Interpretation Guide. The Johns Hopkins University. 1996
Bergner M, Bobbitt RA, Carter WB, et al. The Sickness Impact Profile: Development and final revision of a health status measure. Medical Care 1981;19(8):787-805
Bergner M, Bobbitt RA, Kressel S, et al. The Sickness Impact Profile: Conceptual formulation and methodology for the development of a health status measure. International Journal of Health Services 1976;6(3):393-415
Bergner M, Bobbitt RA, Pollard WE, et al. The Sickness Impact Profile: Validation of a health status measure. Medical Care 1976;14(1):57-67
Carter WB, Bobbitt RA, Bergner M, et al. Validation of an interval scaling: The Sickness Impact Profile. Health Services Research 1976 Winter;11(4):516-28
Pollard WE, Bobbitt RA, Bergner M, et al. The Sickness Impact Profile: Reliability of a health status measure. Medical Care 1976;14(2):146-55
Patrick DL, Devo RA. Generic and diseasespecific measures in assessing health status and quality of life. Medical Care 1989;27(3 Suppl):S217-32
Gilson BS, Erickson D, Chavez CT, et al. A Chicano version of the Sickness Impact Profile (SIP). A health care evaluation instrument crosses the linguistic barrier. Cult Med Psychiatry 1980;4(2):137-50