The Arthritis Impact Measurement Scales (AIMS) have been developed to assess the health status of arthritis patients. In this study, the self-administered AIMS questionnaire, which includes scales designed to measure the physical, psychologic, and social aspects of health status, was completed by 625 patients with various forms of arthritis. A comprehensive battery of analytic techniques was used to investigate the performance of these scales in this large sample. The results confirmed the reliability and validity of the AIMS instrument. They also showed that AIMS performs well ia at least 4 major types of arthritis, in a range of sociodemographic groups, and across time. These findings emphasize the strengths of the AIMS approach and suggest that the instrument will prove useful as a tool to assess arthritis outcome in a wide variety of clinical settings.The Arthritis Impact Measurement Scales (AIMS) are batteries of health status questions that are designed to assess the physical, emotional, and social well-being of individuals with rheumatic diseases. The self-administered AIMS instrument has been developed to improve the measurement of patient outcome in arthritis (1). Although the AIMS approach is based on previous work in health status measurement (2-6), the measurement properties of any new instrument must be documented before it is widely accepted and applied. Our preliminary findings on the AIMS instrument indicated acceptable levels of reliability and validity (7), but they were based on a relatively small sample size and were limited in analytic and clinical scope. This report reexamines the reliability and validity of the AIMS instrument through the use of a larger sample and a variety of additional analytic approaches. It presents new measures of test-retest reliability and estimates of construct validity, based on clinical data. This report also attempts to estimate the clinical applicability of the AIMS approach by providing the first descriptions of AIMS performance in the major rheumatic diseases, in various sociodemographic groups, and across time. MATERIALS AND METHODSInstrument description. The current AIMS instrument contains 45 health status questions, grouped into 9 component scales: Mobility, Physical Activity, Dexterity, Household Activities, Activities of Daily Living, Anxiety, Depression, Social Activity, and Pain. The scales contain 4-7 items, and each item, depending on the phrasing of the question, contains 2-6 possible responses. Item responses are summed by group to produce scale scores and then brought to a normal standard of 0-10 for further analysis. The instrument used was identical to that described in our original report, with 2 exceptions. First, the original Social Role scale has been renamed Household Activities to better reflect the contents of the scale. The items it contains are

We found that 36% of 815 consecutive patients on a general medical service of a university hospital had an iatrogenic illness. In 9% of all persons admitted, the incident was considered major in that it threatened life or produced considerable disability. In 2% of the 815 patients, the iatrogenic illness was believed to contribute to the death of the patient. Exposure to drugs was a particularly important factor in determining which patients had complications. Given the increasing number and complexity of diagnostic procedures and therapeutic agents, monitoring of untoward events is essential, and attention should be paid to educational efforts to reduce the risks of iatrogenic illness.

A multidimensional index that measures the health status of individuals with arthritis has been developed. The Arthritis Impact Measurement Scales (AIMS) are a combination of previously studied and newly created health status scales which assess physical, emotional, and social well-being. The self-administered AIMS questionnaire has been pilot tested in a mixed arthritis population. Results indicate that the instrument is practical and that it generates scalable, reliable, and valid measures of both aggregated and disaggregated health status. The AIMS approach to health status measurement should prove useful for evaluating the outcomes of arthritis treatments and programs.The worth of a new medical practice or policy ultimately depends upon the effect it produces on health (1,2). Thus, the development of reliable, valid, and practical outcome measures is a priority area for health services research. Although the end results of health care can be assessed by measuring a variety of parameters such as satisfaction and cost, health status is the most important component of outcome (3,4).

Two independently developed patient outcome measurement instruments were administered to forty-eight subjects with rheumatoid arthritis using a random cross-over design. The independent estimates of physical disability and pain are highly correlated. Each instrument displayed highly significant relationships with global health, providing evidence for convergent validity. The results demonstrate that health status is composed of at least three major dimensions: physical disability, psychological disability, and pain. (Am J Public Health 1984; 74:159-161.) The chronic diseases affect the quality of life as well as the duration of life, and thus require for their assessment the ability to measure health status effectively.'-9 Two independent instruments have recently been,'°0" developed to assess patient outcome in arthritis and other chronic diseases the Health Assessment Questionnaire (HAQ), and the Arthritis Impact Measurement Scales (AIMS); both are selfadministered. This study compares these instruments in a randomized crossover study, demonstrates convergent validity for the health status concept, and identifies major components of patient outcome. Methods Instrument DescriptionThe HAQ disability and pain instruments consist of 21 questions grouped into nine components graded in an ordinal fashion from 0 to 3.* The AIMS instrument is composed of 49 items. The initial 45 items are summed into nine scales. Each scale is indexed from zero to ten (minimum to maximum disability).** The content of the two instruments overlaps by about 65 per cent. In all cases, however, the actual questionnaire items are different. Both instruments contain a single horizontal visual analog scale assessing the patient's perception of arthritis status, providing a "global health estimate." *(I) dressing and grooming; (2) arising; (3) eating; (4) walking; (5) reach; (6) personal hygiene; (7) gripping and grasp; (8) activities; (9) pain. **(l) mobility; (2) physical activity; (3) activities of daily living (ADL); (4) dexterity; (5) household activities; (6) pain; (7) social activity; (8) Both instruments have undergone extensive validation. l0.-3*** All nine AIMS scales were highly correlated with physician produced estimates of health status, and specific scales correlated highly with standard measures of physical function. 13 Correlations of the HAQ battery against observed patient performance ranged from 0.47 to 0.88.10,12 Study Design Forty-eight patients with rheumatoid arthritis were administered the two instruments by mail at an average 18-day interval in random order. Subjects were randomly selected from a community-based study group of 384 patients. 12 Scores for items, component scales, and aggregate scales of both instruments were calculated. The order of administration did not affect results. Factor analysis on both AIMS and HAQ scales focused on standard principal factor techniques with varimax rotation.'4 ResultsThe study group was typical of rheumatoid arthritis in being predominantly White (89 per cent), f...