Psychometric Properties of the Portuguese Version of the Checklist of Individual Strength (CIS20-P)

Aim: The Checklist of Individual Strength (CIS20) is a well validated measure of fatigue severity, which has been adapted in several languages. As Portuguese is one of the most widely spoken languages in the world it is important to have a Portuguese adaptation of the CIS20. Method: Four hundred and thirty healthy Portuguese adults and 89 patients with chronic fatigue (CF) filled out the Portuguese version of the CIS20 (CIS20-P). The CF patients and a subsample of the healthy adults also filled out the SF-12v2 assessing health-related quality of life. Results: The CIS20 four-factor structure was confirmed (subjective experience of fatigue, concentration, motivation and physical activity scales). In general, internal consistency estimates were satisfactory, with the exception of the motivation scale. Moreover, a higher degree of fatigue severity was significantly associated with lower vitality and physical and psychological health-related quality of life. Conclusion: Our results indicate that the CIS20-P is a reliable and valid measure of fatigue severity. Future studies should establish Portuguese cut-off points for (sub)clinical levels of fatigue.