Checklist Individual Strength

The Checklist Individual Strength (CIS) is a 20-item fatigue questionnaire developed by the Dutch research team of Vercoulen et al. in 1994. The questionnaire has been translated into multiple languages and has been used in various illnesses, including myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). An 8-item subscale of CIS that measures subjective fatigue regularly acts as a primary outcome in randomized trials on the effects cognitive behavior therapy in ME/CFS. The use of this subscale in a ME/CFS patient population however has been criticized for displaying ceiling effects.