Translation emphasizes the comprehensibility and appropriateness of the language in the Korean cultural context. The process of translating the SIS 3.0 into Korean included the following steps: The SIS 3.0 was translated into Korean by two independent native Korean speakers with excellent knowledge of English, and organized by a translation committee which comprised two rehabilitation medical doctors and a psychologist. The first K-SIS 3.0 was agreed by consensus. This version was back-translated into English by a Korean native with good knowledge of English, who did not have access to the original version of the SIS. The first back-translation was compared with the original version, and modifications were made to eliminate all discrepancies between the original and the back-translated versions (Fig. 1).

This study included 70 stroke patients hospitalized at the National Rehabilitation Center of Korea. Patients were evaluated using the Mini-Mental State Examination (MMSE), the National Institutes of Health Stroke Scale (NIHSS), the Modified Barthel Index (MBI), and the Hospital Anxiety and Depression Scale (HADS). Health-related quality of life was evaluated with the Short Form Health Survey (SF-36), and the K-SIS 3.0. The subjects were evaluated twice (test interval, 15 days) to establish the test-retest reliability of K-SIS.

Inclusion criteria were (1) stroke (subacute, chronic) diagnosed on the basis of clinical and radiologic findings (brain computed tomography and/or magnetic resonance imaging); (2) age greater than 20 years; (3) hospitalization at the National Rehabilitation Center of Korea; and (4) sufficient cognitive ability to understand the questionnaire. The following criteria were excluded from the study: (1) severe disability caused by a previous neurologic disorder; (2) comorbidity with severe systemic illness (e.g., cancer, autoimmune disease); and (3) severe pre-existing neurological deficits.

The MMSE measures the cognitive functions, including memory, orientation to place and time, naming, reading, copying (visuospatial orientation), writing, and the ability to follow a 3-stage command. This instrument has 19 items, with scores ranging from 0 to 30 points [10].

NIHSS is a 15-item stroke scale that provides a quantitative measure of the components of a neurologic examination. The NIHSS evaluates the patient's level of consciousness, external ocular movements, visual fields, facial palsy, strength of extremities, coordination, sensory loss, language (aphasia), dysarthria, extinction, and inattention. The score ranges from 0 to 42, with higher scores indicating greater impairment [11]. The MBI has been widely used to evaluate the activities of daily living (ADL) in stroke patients. The MBI measures 10 items of ADL related to self-care and mobility: control of bowels and bladder, grooming, toileting, feeding, transfer, mobility, dressing, stairs, and bathing. The MBI score ranges from 0 to 100, with lower scores indicating greater dependency. The validity and reliability of this tool is well established [12]. The HADS consists of 7 items for the assessment of anxiety, and 7 for depression, with each item scored from 0 (no problem) to 3 (severe problem). Scores on individual items are summed to calculate a score for anxiety (HADS-A) and for depression (HADS-D). Scores over 11 points on a subscale are indicative of mood disturbance [13]. The SF-36 is a generic health-related quality of life measure that includes 8 domains for the assessment of physical functioning, role limitations due to physical problems, bodily pain, general health perception, vitality, social functioning, role limitations due to emotional problems, and emotional well-being. Scores for each domain range from 0 to 100, where higher values indicate better functioning. We used the Korean version of SF-36 [14]. The SIS 3.0 is a 59-item self-report assessment of stroke outcome, used to assess health-related quality of life. The SIS has 8 domains: strength, hand function, mobility, physical and instrumental activities of daily living (ADLs and IADLs), memory and thinking, communication, emotion, and social participation. Scores for each domain range from 0 to 100, where higher scores indicate a better health-related quality of life. The strength items are rated in terms of strength; memory, communication, ADLs/IADLs, mobility, and hand function items in terms of amount of difficulty; and emotion and social participation items in terms of frequency. Four of the subscales (strength, hand function, ADLs/IADLs, and mobility) are combined as a physical domain. The SIS 3.0 also includes a question to assess the patient's global perception of recovery. The respondent is asked to rate his or her percentage of recovery on a visual analog scale of 0 to 100, where lower scores indicate lower perceived recovery [15].

Data analysis was carried out using SPSS ver. 15.0 for Windows (SPSS Inc., Chicago, IL, USA). The data were analyzed in a descriptive as well as inferential manner. The categorical variables were presented as absolute values and percentages, and the numeric variables as means and standard deviations. Univariate analysis was first carried out between each predictor and the SIS domain to identify the variables included in the multivariate model. Interclass correlation coefficient (Spearman's rho) was calculated for the test-retest reliability analysis. Internal consistency was analyzed with Cronbach's alpha test. A value of p less than 0.05 was considered statistically significant.

Internal consistency of the SIS 3.0 (Cronbach's alpha) was obtained, and all domains had good co-efficiency, above the threshold of 0.70 (stroke recovery could not be evaluated as it is a 1-item scale) (Table 3). Test-retest reliability of SIS 3.0 resulted from the correlation (Spearman's rho) of the same domain scores obtained on the 1st and 2nd assessments. Results were above 0.5, with the exception of the social participation and mobility (Table 4).

Concurrent validity of K-SIS 3.0 was assessed using the SF-36 compared to the same or similar domains. The strength domain of K-SIS 3.0 had a positive correlation with physical function (Spearman's rank correlation coefficients, ρ=0.356), bodily pain (ρ=0.318), general health (ρ=0.281), and physical domain (ρ=0.401) of the SF-36. Hand function domain of K-SIS 3.0 correlated with physical function (ρ=0.283), general health (ρ=0.353), and mental health domain (ρ=0.416) of the SF-36. Mobility domain of K-SIS 3.0 had a positive relationship with physical roles (ρ=0.361), general health (ρ=0.480), emotional roles (ρ=0.528), and mental domain of SF-36 (ρ=0.612). The memory domain of K-SIS 3.0 correlated with mental health (ρ=0.237) and physical domains of the SF-36 (ρ=0.534). Social participation correlated with physical function (ρ=0.378), physical roles (ρ=0.335), and physical domain (ρ=0.389). The stroke recovery domain of K-SIS 3.0 had a positive correlation with general health (ρ=0.442), role physical (ρ=0.377), vitality (ρ=0.329), and physical domains of the SF-36 (ρ=0.488). A weak association was observed between the emotional domain of K-SIS 3.0 and emotional roles of SF-36 (Table 5). Concurrent validity was observed between K-SIS 3.0 and other scales with the same or similar domains. The strength (ρ=0.370), hand function (ρ=0.556), ADL/I-ADL (ρ=0.628), and mobility domains (ρ=0.613) of K-SIS 3.0 correlated with MBI. Hand function, mobility, ADL/IADL, memory, communication, emotion, and stroke recovery domains of K-SIS 3.0 also correlated with HADS-A and HADS-D. Mobility (ρ=0.352) and ADL/I-ADL domains (ρ=0.247) of K-SIS 3.0 were correlated with MMSE. All domains of K-SIS 3.0, except the emotion and memory domains, correlated with NIHSS (Table 6).