Demographic (age, gender, height, weight), CSI-J, and four pain-related outcomes [pain duration, health-related quality of life (QOL), pain intensity, and pain interference] were assessed in all participants. A test-retest reliability of the CSI-J was determined with a time interval of 1 week. These domains were selected because patients whose presenting symptoms may be related to a CSS (e.g. chronic whiplash-associated disorders, fibromyalgia, and PTSD) showed significant relationships between CS outcome and QOL, pain intensity, and disability [33 (link), 40 (link)–42 (link)].
The CSI-J consists of two parts: A and B. Part A is a 25-item self-report questionnaire designed to assess health-related symptoms that are common to CSSs. Each item is rated on a 5-point Likert-type scale (0 = never and 4 = always), with total scores of 0–100. Part B (which is not scored) is designed to determine whether one or more specific disorders, including seven separate CSSs, have been previously diagnosed [restless leg syndrome, chronic fatigue syndrome, fibromyalgia, temporomandibular joint disorder, migraine or tension headaches, irritable bowel syndrome, multiple chemical sensitivities, neck injuries (including whiplash), anxiety or panic attacks, and depression].
Health-related QOL was measured using EuroQol 5-dimension (EQ-5D) [43 (link)]. EQ-5D was developed as an instrument that is not specific to disease, but standardized, and can be used as a complement to existing health-related QOL measures [44 (link)]. It comprises the following five dimensions: mobility, self-care, usual activities, pain/discomfort, and anxiety/depression. Each dimension has three grades (no problems, some problems, and extreme problems), which can generate a single index value for each health state. These values are numbers on a scale with 1 for full health and 0 for being dead. Tsuchiya et al. showed the Japanese value set [45 (link)].
Pain intensity and pain interference were measured using the Brief Pain Inventory (BPI) [46 (link),47 (link)]. It consists of four pain intensity and seven pain interference items. These items were presented with 0–10 scales, with 0 = no and 10 = worst (completely). From these, individual pain intensity and pain interference scores are calculated by averaging. The validation and clinical utility of BPI has been evaluated for several disorders [48 (link)–50 (link)]. To investigate the prevalence rates of CS severity levels, we referred to the five categories with increasing severity [33 (link)]. The authors reviewed the score distributions of previously published CSI study samples, including those with no CSS diagnosis, those with a single CSS diagnosis, those with multiple CSS diagnoses, and a group of nonpatient comparison subjects. Through empirical reasoning and deduction, using these score distributions as a guide, the CSI was divided into five categories with increasing severity: subclinical (0–29), mild (30–39), moderate (40–49), severe (50–59), and extreme (60–100).
The CSI-J consists of two parts: A and B. Part A is a 25-item self-report questionnaire designed to assess health-related symptoms that are common to CSSs. Each item is rated on a 5-point Likert-type scale (0 = never and 4 = always), with total scores of 0–100. Part B (which is not scored) is designed to determine whether one or more specific disorders, including seven separate CSSs, have been previously diagnosed [restless leg syndrome, chronic fatigue syndrome, fibromyalgia, temporomandibular joint disorder, migraine or tension headaches, irritable bowel syndrome, multiple chemical sensitivities, neck injuries (including whiplash), anxiety or panic attacks, and depression].
Health-related QOL was measured using EuroQol 5-dimension (EQ-5D) [43 (link)]. EQ-5D was developed as an instrument that is not specific to disease, but standardized, and can be used as a complement to existing health-related QOL measures [44 (link)]. It comprises the following five dimensions: mobility, self-care, usual activities, pain/discomfort, and anxiety/depression. Each dimension has three grades (no problems, some problems, and extreme problems), which can generate a single index value for each health state. These values are numbers on a scale with 1 for full health and 0 for being dead. Tsuchiya et al. showed the Japanese value set [45 (link)].
Pain intensity and pain interference were measured using the Brief Pain Inventory (BPI) [46 (link),47 (link)]. It consists of four pain intensity and seven pain interference items. These items were presented with 0–10 scales, with 0 = no and 10 = worst (completely). From these, individual pain intensity and pain interference scores are calculated by averaging. The validation and clinical utility of BPI has been evaluated for several disorders [48 (link)–50 (link)]. To investigate the prevalence rates of CS severity levels, we referred to the five categories with increasing severity [33 (link)]. The authors reviewed the score distributions of previously published CSI study samples, including those with no CSS diagnosis, those with a single CSS diagnosis, those with multiple CSS diagnoses, and a group of nonpatient comparison subjects. Through empirical reasoning and deduction, using these score distributions as a guide, the CSI was divided into five categories with increasing severity: subclinical (0–29), mild (30–39), moderate (40–49), severe (50–59), and extreme (60–100).
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