Review ArticleA study compared nine patient-specific indices for musculoskeletal disorders
Introduction
Researchers investigating the burden of illness and benefits of care are increasingly interested in the patient's perspective as determined by self-reports of health and health-related quality of life (HRQoL). These tools can be subdivided into two groups: first, those instruments with fixed items (fixed-item measures) such as the popular Short Form 36 (SF-36) [1], or disease-specific instruments such as the arthritis-specific Health Assessment Questionnaire (HAQ) [2], and second, those patient-specific instruments that involve individuals generating their own, possibly quite unique, items for the HRQoL questionnaire [3], [4], [5], [6].
Each approach has its strengths and limitations. Data produced by the fixed-item tools are convenient and relatively simple to categorize and compare across patients and settings; however, the same fixed-item instruments may miss issues important to a particular patient while including irrelevant ones. Because fixed-item measures are often difficult to interpret at the individual patient level, clinicians rarely rely on them as routine indicators for problem identification or treatment monitoring, preferring to ask patients directly what is wrong and if they are better [7].
Although patient-specific indices offer the advantage of identifying the salient issues for each patient, and are more likely to focus just on the relevant materials, they are not yet universally accepted by researchers. One disadvantage put forward is that, without standardization of the items under study in the content, the scales are usually not the same in each patient (Table 1). If this is so, the numeric score may not hold a common meaning, and the value of analyzing the data statistically and calculating parameters such as means and correlations is questionable. This parallels the problem that exists when comparisons are made across different fixed-item scales that fulfill the usual criteria of acceptable measurement but still give very different impressions of health in the same sample [8], [9]. Results across studies using different fixed-item scales are considered incomparable because of the different outcome scales. The same argument could be true for the different patient-specific measures in a sample of patients.
Even within the patient-specific measures available, there appear to be differences in the generation of items. One might ask for the most difficult tasks [10], another might encourage content across prespecified domains [11]. Still others encourage attribution of the difficulty to a specific pathology (e.g., hip pain) [12]. These differences could lead to elicitation of different items for a given patient, and suggest differences in the phenomenon or phenomena that these patient-specific scales are tapping.
Important decisions regarding therapy and health policy are based on patient outcomes, so the question of whether to use standardized or patient-specific tools is critical. A measure of outcome that accurately reflects a patient's perceptions of his or her quality of life and has individual meaning and relevance would shed light on the most important aspects of disease. Patient-specific indices are one way to reach that individualized level. A variety of patient-specific indices exist, but to date critical appraisals comparing these measures have not addressed the degree to which they are conceptually similar or different, or the issues around summarizing measurement properties in a scale that is unique for each client.
Our objective was to do a systematic review of the literature on existing patient-specific measures and provide a critical appraisal of their concept, content, and sensibility. We also wanted to provide clinicians and researchers with information about the advantages and limitations of these measures in describing and evaluating change in patients with musculoskeletal disorders.
Section snippets
Methods
A systematic review of the literature was undertaken to identify as many patient-specific instruments as possible. Medline was searched for studies published between 1966 and the end of 2001 using the following subject headings: questionnaires, outcome assessment, treatment outcome, patient satisfaction, quality of life, health status, health services research with human subjects, and musculoskeletal disorders. Headings used in a Cinahl search covering 1982 to 2001 were questionnaires,
Results
Of 12 patient-specific questionnaires initially identified, three were excluded: the popular Goals Attainment Scale (GAS) because it is not self-reported [18], and two others because they are transitional rather than state indices [19], [20].
Discussion
This critical appraisal of nine patient-specific indices for use in persons with musculoskeletal disorders reveals important differences in terms of the underlying concepts, the domains covered, the item-generation techniques, and the scoring (response scale, methods) in each scale. We conclude that the nine indices would generate different responses and likely scores for the same patient, despite the fact that they all include patient-generated items. Therefore, consumers should be aware that
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