Measuring the physical activity level and pattern in daily life in persons with chronic fatigue syndrome/myalgic encephalomyelitis: a systematic review

Background: A lower activity level and imbalanced activity pattern are frequently observed in persons with chronic fatigue syndrome (CFS)/myalgic encephalomyelitis (ME) due to debilitating fatigue and post-exertional malaise (PEM). To provide an optimal treatment strategy, insight into a patient's current physical activity level and pattern is necessary and identification of reliable and valid measures or scales measuring physical activity level and pattern in this population is warranted.

Objective: To identify measures or scales used to evaluate activity level and/or pattern in patients with CFS/ME and review their psychometric properties.

Methods: A systematic literature search was performed in the electronic databases PubMed and Web of Science until 12 October 2016. First, articles including relevant measures were identified. Secondly, psychometric properties of relevant measurement instruments were extracted and rated based on the COSMIN checklist.

Results: The review was performed and reported according to PRISMA statement. A total of 51 articles and 15 unique measurement instruments were found, but only three instruments have been evaluated in patients with CFS: the Chronic Fatigue Syndrome-Activity Questionnaire (CFS-AQ), Activity Pattern Interview (API) and International Physical Activity Questionnaire-Short Form (IPAQ-SF), all self-report instruments measuring physical activity level.

Conclusions: The IPAQ-SF, CFS-AQ and API are all equally capable of evaluating the physical activity level, but none of these are optimal to use. Although often used as gold standard to capture physical activity patterns, activity monitors have not yet been evaluated in these patients. More research is needed to evaluate the psychometric properties of existing instruments, including activity monitors.