Finding a clinical assessment scale - Physical Medicine and Rehabilitation

Description:

The SF-36 is a quality-of-life questionnaire developed as a part of the Medical Outcomes Study to assess 8 physical and mental health concepts as seen from the respondent's point of view.

These concepts are: (1) limitations in physical activities because of health problems (Physical Functioning) with 10 items, (2) limitations in social activities because of physical or emotional problems (Social Functioning) with 2 items, (3) limitations in usual role activities because of physical health problems (Physical Role Functioning) with 4 items, (4) bodily pain (Bodily Pain) with 2 items, (5) psychological distress and well-being (Mental Health) with 5 items, (6) limitations in usual role activities because of emotional problems (Psychological Role Functioning) with 3 items, (7) energy and fatigue (Vitality) with 4 items, and (8) general health perceptions (General Health).

These 8 domains are relevant to general functional status and well-being.

The survey was designed for self-administration by people 14 years of age and older or for administration by a trained interviewer in person or by telephone.

For each scale, item scores are coded, summed, and transformed, with final values (expressed as a percentage) ranging from 0 (worst health) to 100 (best health).

The SF-36 was designed for use in clinical practice and research, health policy evaluations, and general population surveys. It was also constructed to compare functional health and wellbeing across patient and general populations, and to evaluate and compare the benefits of alternative treatments.

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Author : Medical Outcomes Trust (MOT), Health Assessment Lab (HAL) and QualityMetric Incorporated.

Psychometric properties:

General comment on reliability:

The SF-36 has been studied in different populations:
Healthy people [9, 16], Older people [11, 14], Patients with vestibular disease [17], Patients with rheumatoid arthritis [18], Patients after stroke [15, 19, 20, 29, 40], Schizophrenic outpatients [21, 32], Traumatic brain injury [30, 36, 39, 52], Asthma patients [31], Multiple sclerosis [35], Spinal cord injury [43, 51, 54], Parkinson disease [10, 47, 50, 58], Chronic whiplash syndrom [53], Adults with intradural primary spinal tumors [57].

Construct validity was demonstrated by clear differences across all eight SF-36 scales for patients with identified health problems [15]. It was also correlated with American College of Rheumatology (ACR) core disease activity measures [18].

The mental health SF-36 subscales had poor discriminant validity, compared with the physical functioning scale that demonstrated good discriminant validity [21].

Item-scale correlations showed that all items fulfilled the minimum requirements for convergent and discriminant validity [36, 52].

Results suggest that the two summary measures (Physical component summary (PCS) and mental component summary (MCS)) may be useful in most studies and that their empiric validity, relative to the best SF-36 scale, will depend on the application [13].

The component scales of the SF-36 demonstrated good discrimination between people with and without health conditions, including those with medical and those with psychiatric types of conditions [9].

Excellent discriminant validity established between Physical capacity score (PCS) and Mental capacity score (MCS) constructs; excellent convergent validity between impairment severity and PCS ; excellent divergent validity between impairment severity and MCS scores [43].

Good responsiveness of the SF-36 [18, 53] but the DHI (Dizziness Handicap Inventory ) was more responsive to change than the SF-36 in a population of individuals with vestibular disease [17].

The responsiveness of the SF-36 was poor in evaluating change in moderate to severely disabled patients with multiple sclerosis participating in a programme of inpatient rehabilitation [35]. Most SF-36 subscales were sensitive to change between 1 and 3 months post-stroke, but none detected change between 3 and 6 months in patients after stroke [40].

SF-36 demonstrated good retest reliability [14, 18, 32, 41, 47, 57].

All eight scales of the SF 36 questionnaire show high reliability when used to monitor health in groups of patients (with ulcerative colitis , varicose veins, low back pain, menorrhagia) [5].
Moderately to highly reliable in a population of individuals with vestibular disease [17].

The reproducibility of the domains of the SF-36 was qualitatively similar for all the domains except mental health. Reproducibility was better when the patient completed the questionnaires than when a proxy did. Both the EuroQol and SF-36 have acceptable and qualitatively similar test-retest reliability. [19]

SF-36 demonstrated good internal consistency among older adults [14], schizophrenic outpatients [21], at the early post stroke phase [40], and after traumatic brain injury [52] or spinal cord injury [54]. It was adequate to excellent across all domains in patients with spinal cord injury [43].

The health concepts measured demonstrated good internal consistency [36].
The eight scales of the SF-36 formed factors as predicted in the general health dimensions of physical and mental health [9].

The internal consistency of the Nottingham Health Profile scales was lower than the scales of the SF-36. The SF-36 exhibited the best ability to discriminate between groups. the SF-36 appeared to be the most suitable measure of health status in a relatively healthy population [16].

Mailed surveys pose a problem of response among older adults, a problem not unique to the SF-36 ( 60% of questionnnaires returned ) [14]. Those who were younger were more likely to refuse to participate when the mail mode was adopted, while older people were more likely not to consent to the telephone mode [22].

Postal administration of the SF-36 is not appropriate for assessing quality of life of older stroke patients [21].

Hayes et al. have suggested that some revisions to the format of the questions may be needed to make the SF-36 more acceptable as a self-report instrument for older adults. [11]

The SF-36 avoids the "ceiling effect" of most disability scales and provides a valid measure of physical and mental health after stroke, but it does not appear to characterize well social functioning [15].

The SF-36 has some limitations as an outcome measure in multiple sclerosis [35].

Floor effects were high (> 15%) for these two scales (physical and role emotional scales) and for the social functioning and physical functioning scales in older stroke patients. [20]

The SF-36 may be particularly useful in evaluating associated musculoskeletal injuries, which might otherwise be overlooked by MTBI (mild traumatic brain injury) health care providers [30].

SF-36 is valid as useful measure of asthma patient's HRQoL (Health Related Quality of Life). Severity of disease, as measured by health care utilization, was significantly associated with HRQoL.

The perceptions of functioning can be valuable indices of disease burden and can help to demonstrate the effectiveness of newer antipsychotic medications such as olanzapine. [32]

The use of the SF-36 in individuals with PD can be recommended when eight subscales are used and reported [50] but the two SF-36 summary measures were not found to be valid indicators of physical and mental health [47, 50].

The SF-36 walk wheel is a simple, pragmatic modification of the SF-36 PF items, which addresses some problems of content validity and floor effect for SCI subjects and greatly improves responsiveness, particularly for those with tetraplegia [51].

SF-36 provides valid and reliable data for patients with IPSTs (intradural primary spinal tumors ) and that the survey can be used appropriately to evaluate these patients [57].

The validity of using the written form of the SF-36 on a sample of patients with chronic mental illness was demonstrated. [21].

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