The assessment of fatigue: Psychometric qualities and norms for the Checklist individual strength

J Psychosom Res. 2017 Jul;98:40-46. doi: 10.1016/j.jpsychores.2017.05.007. Epub 2017 May 8.


Objective: The Checklist Individual Strength (CIS) measures four dimensions of fatigue: Fatigue severity, concentration problems, reduced motivation and activity. On the fatigue severity subscale, a cut-off score of 35 is used. This study 1) investigated the psychometric qualities of the CIS; 2) validated the cut-off score for severe fatigue and 3) provided norms.

Methods: Representatives of the Dutch general population (n=2288) completed the CIS. The factor structure was investigated using an exploratory factor analysis. Internal consistency and test-retest reliability were determined. Concurrent validity was assessed in two additional samples by correlating the CIS with other fatigue scales (Chalder Fatigue Questionnaire, MOS Short form-36 Vitality subscale, EORTC QLQ-C30 fatigue subscale). To validate the fatigue severity cut-off score, a Receiver Operating Characteristics analysis was performed with patients referred to a chronic fatigue treatment centre (n=5243) and a healthy group (n=1906). Norm scores for CIS subscales were calculated for the general population, patients with chronic fatigue syndrome (CFS; n=1407) and eight groups with other medical conditions (n=1411).

Results: The original four-factor structure of the CIS was replicated. Internal consistency (α=0.84-0.95) and test-retest reliability (r=0.74-0.86) of the subscales were high. Correlations with other fatigue scales were moderate to high. The 35 points cut-off score for severe fatigue is appropriate, but, given the 17% false positive rate, should be adjusted to 40 for research in CFS.

Conclusion: The CIS is a valid and reliable tool for the assessment of fatigue, with a validated cut-off score for severe fatigue that can be used in clinical practice.

Keywords: Checklist individual strength; Chronic fatigue; Fatigue questionnaire; Patient-reported outcomes; Psychometrics; Reliability and validity.

MeSH terms

  • Adult
  • Checklist / methods*
  • Fatigue / diagnosis*
  • Female
  • Humans
  • Male
  • Psychometrics / methods*
  • Quality Control
  • ROC Curve
  • Reproducibility of Results
  • Surveys and Questionnaires