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Chapter 7 Measuring Functional Status in Rheumatic Diseases

Manual of Rheumatology and Outpatient Orthopedic Disorders

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Chapter 7 Measuring Functional Status in Rheumatic Diseases

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C. Ronald MacKenzie and Theodore Pincus

Methodologic requirements
Demonstrated clinical applications
Functional status questionnaires

Functional status refers to a patient's level of performance in the activities of daily living. Although functional status is clearly of major importance to patients and health care professionals, it is not assessed with laboratory tests, radiographs, and other imaging procedures and therefore has not been formally measured in traditional medical care settings. During the last decade , several questionnaire instruments have been studied extensively to assess functional status in individual patients in clinical research, clinical trials, and clinical practice. The development of these questionnaires has been based on rigorous scientific methods and provides new insights into the long- term course of various rheumatic diseases. In this chapter, a brief review is presented of the methodologic requirements and clinical applications of functional status questionnaires, as well as a brief description of several of the most widely used questionnaires.

I. Methodologic requirements. Applications of functional status measures include quantitative evaluation of a patient's baseline level of function for comparison over time in clinical trials or clinical practice, discrimination between individuals (or groups) according to a given component or criterion of functional status, and prediction of a subsequent functional level in patients at risk for functional compromise in the future. Although the structural characteristics of the functional measures vary depending on the purpose for which the scale is to be used, several requirements pertain to all questionnaires.

1. Quantification. The questionnaire should provide a quantitative score, preferably with an absolute zero or normal value, to allow for arithmetic and statistical comparisons.
2. Standardized data collection. The questionnaire should be collected according to an established methodology, analogous to a laboratory procedure, including rules for distribution, recording, and scoring of the data.
3. Reliability. Reliability or consistency includes both of the following:
   1. External consistency. Similar results are seen when an index is applied by different users at the same time and by the same person (including the patient) at different times.
   2. Internal consistency. Specific scale items measuring similar attributes elicit the same responses from the patients.
4. Validity. The questionnaire should measure what it purports to measure.
   1. Face validity (i.e., what is noted on simple inspection of the questionnaire makes sense).
   2. Content validity (i.e., the questionnaire represents a specified construct, in this case functional capacity).
   3. Criterion validity (i.e., agreement of the index with another measure of the same phenomenon , the gold standard ).
5. Responsiveness. Responsiveness or sensitivity to change refers to the capacity of a questionnaire to detect a change in patient status when a clinical impression exists that a change has occurred (e.g., with the application of an effective therapy ), and to indicate no change when no change in functional status is seen.
6. Feasibility. Although not generally emphasized , a most important consideration in the use of questionnaires in clinical settings involves feasibility ”that is, the questionnaire should be brief, patient-friendly, nonthreatening, and easily distributed and collected by the office staff.

II. Demonstrated clinical applications. Functional status questionnaires correlate well with traditional end points of evaluation in the rheumatic diseases, such as joint counts, radiographic findings, and results of various laboratory investigations. Moreover, questionnaires appear to provide useful information concerning a number of important clinical phenomena that have been difficult or impossible to quantify with traditional measures. These include the following:

1. Documentation and prediction of long-term functional declines and work disability associated with the rheumatic diseases.
2. Prediction of mortality in patients with rheumatoid arthritis, including identification of patients with projected 5-year survivals in the range of 50%, as in patients with cardiovascular and neoplastic diseases.
3. Identification of health service utilization by patients with rheumatic diseases.
4. Provision of measurable insights into psychosocial problems of patients with rheumatic diseases.
5. Detection of changes in clinical status in patients enrolled in clinical trials, as effective as physical or laboratory measures. Although the use of these questionnaires has been largely limited to clinical research, the demonstrated utility of self- reported questionnaires in patient assessment and monitoring has led to their more recent use in routine patient evaluation as adjuncts to patient evaluation.

III. Functional status questionnaires. Many questionnaires have been developed to measure various aspects of functional status in patients with the rheumatic diseases. Among the most widely used measures of overall functional capacity, all of which meet appropriate methodologic standards, are the following:

1. Health Assessment Questionnaire (HAQ). This questionnaire measures performance in activities of daily living, emphasizing difficulty and the need for equipment and physical assistance to complete common tasks . Scores on eight subscales derived from 20 questions are averaged to create a disability index with scores ranging from 0 to 3 on each scale. A visual analog subscale measures intensity of pain. The HAQ is self-administered and takes 8 to 10 minutes to complete.
2. Modified Health Assessment Questionnaire (MHAQ). This self-administered questionnaire includes a modification of the HAQ; the original 20 questions were reduced to eight, and supplemental questions concerning patients' perceived satisfaction with their health, global status, morning stiffness, pain, gastrointestinal symptoms, and fatigue were added.
3. Arthritis Impact Measurement Scale (AIMS). The AIMS questionnaire consists of 48 multiple-choice questions grouped into nine subscales measuring physical, social, and mental health. The questionnaire is comprehensive and evaluates a patient's performance across the entire spectrum of functional activity, including general physical activity, lower extremity function, household activities, activities of daily living, basic self-care techniques, interaction with friends and family, anxiety, depression, and pain. A revision of the questionnaire (AIMS2) has recently been published. In its new form, three scales have been added to evaluate arm function, work, and social support, as have sections to assess satisfaction with function, attribution of problems to arthritis, and self-designation of priority areas for improvement. The possible range of scores on each subscale is 0 to 10, with subscale results averaged to obtain an overall scale. The AIMS takes 20 to 30 minutes to complete.
4. MACTAR Patient Preference Disability Questionnaire. This questionnaire is designed to identify individual disabilities caused by arthritis and assess their relative importance to the patient. Although patients may report any activity of their choosing, they are prompted by an interviewer with a menu of activities, including mobility, self-care, work, and leisure. Activities are subsequently ranked by the patient according to their order of importance. The questionnaire requires about 10 minutes to administer, and standardized scores ranging from 0 (worst function) to 1.0 (optimal function) are calculated. This questionnaire differs from the others in that its design is patient-specific and that an interviewer is required to administer it.

Bibliography

Kirshner BK, Guyatt G. A methodologic framework for assessing health indices. J Chron Dis 1985;38:27.

Liang MH, Jette AM. Measuring functional ability in chronic arthritis: a critical review. Arthritis Rheum 1981;24(1):80.

Meenan RF, et al. AIMS2: the content and properties of a revised and expanded arthritis impact measurement scale's health status questionnaire. Arthritis Rheum 1992;35(1):1.

Pincus T, et al. Self-report questionnaire scores in rheumatoid arthritis reflect traditional physical, radiographic, and laboratory measures. Ann Intern Med 1989;110(4):259.

Wolfe F, Pincus T. Standard self-report questionnaire in routine clinical and research practice: an opportunity for patients and rheumatologists. J Rheumatol 1991;18(5):643.

Books@Ovid
Copyright 2000 by Lippincott Williams & Wilkins
Stephen A. Paget, M.D., Allan Gibofsky, M.D., J.D. and John F. Beary, III, M.D.
Manual of Rheumatology and Outpatient Orthopedic Disorders

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