Subscales used (number of items) | Scale | Range of final scores | |
---|---|---|---|
Fatigue | |||
Checklist Individual Strength (CIS),8 questions refer to the past 14 days | Severity (8) | 7-point Likert scales ‘yes, that is true’ and ‘no, that is not true’ | 8–56 |
Concentration (5) | 5–35 | ||
Motivation (4) | 4–28 | ||
Perceptions | |||
Illness Perception Questionnaire – Revised (IPQ-R),11 translated into Dutch | Personal control (6) | 5-point Likert scales, ‘don't agree at all’ to ‘agree very much’ | 5–30 |
Coherence: insight into fatigue symptoms | Coherence (6) | 5–30 | |
Timeline: expectations of chronicity | Timeline (6) | 5–30 | |
Consequences: impact of fatigue | Consequences (5) | 5–25 | |
Attributions (viral/germ, altered immunity, diet/eating habits; dichotomised for analysis) | Psychological attributiona (6) | 5-point Likert scale, ‘don't agree at all’ to ‘agree very much’ | 6–30 |
Health and other symptoms | |||
Short Form health survey – 3612 | General Health (5) | 5-point Likert scale, ‘very well’ to ‘bad’, and ‘very true’ to ‘very untrue’ | 0–100 |
Pain: questions refer to the past month | Pain (2) | 6-point Likert scale, ‘no’ to ‘very severe’ and 5-point scale ‘not at all’ to ‘very much’ | 0–100 |
Four-Dimensional Symptom Questionnaire,13 questions refer to the past week | Distress (16) | 5-point Likert scales, ‘don't agree at all’ to ‘agree very much’ | 0–32 |
Depression (6) | 0–12 | ||
Anxiety (12) | 0–24 | ||
Somatisation (16) | 0–32 | ||
From the IPQ-R: number of symptoms experienced since the start of fatigue | List of 13 symptoms | Yes/no | 0–13 |
Symptom Checklist,14 questions refer to the past week | Sleep (3) | 5-point Likert scales, 'not at all’ to ‘very much' | 0–15 |
Physical activity | |||
Short Questionnaire to ASsess | Number of days of moderate-intensity physical activity for at least 30 minutes | 0–7 | |
Health-enhancing physical activity (SQUASH),15 questions refer to the past week | Questions on activity of vigorous intensity from subscales Physical activity at work/school and in household | Number of days and average hours or minutes per day | |
Social factors | |||
Checklist for long-term difficulties (adapted from Groningse Lijst Langdurige Moeilijkheden, Dutch16), questions refer to ‘lately experienced chronic difficulties’ | List of 12 domains in which chronic difficulties may be experienced; three boxes leave room for additional difficulties | 4-point Likert scale for severity (no difficulties to severe difficulties) | 0–45 |
Checklist for life events (adapted from Groningse Gebeurtenissen Lijst, Dutch16), questions refer to the past 12 months | List of 28 life events within 8 domains. Three boxes leave room for additional life events | Yes/no | 0–31 |
Social Support Scale17 | 12 items | 5-point Likert scale, ‘Yes, very clear’ to ‘No, certainly not’ | 0–12 |
↵a Subscale developed based on IPQ-R attribution items (stress or worry, my own behaviour, my mental attitude, family problems or worry, my emotional state, my personality); Cronbach's alpha 0.80.