An exploratory study of discrepancies between objective and subjective measurement of the physical activity level in female patients with chronic fatigue syndrome.
OBJECTIVE
To explore the ability of a self-report activity diary to measure the physical activity level (PAL) in female patients with chronic fatigue syndrome (CFS) and whether illness-related complaints, health-related quality of life domains (HRQOL) or demographic factors are associated with discrepancies between self-reported and objectively measured PAL.


METHODS
Sixty-six patients with CFS, recruited from the chronic fatigue clinic of a university hospital, and twenty matched healthy controls wore an accelerometer (Actical) for six consecutive days and registered their activities in an activity diary in the same period. Participants' demographic data was collected and all subjects completed the CFS Symptom List (illness-related complaints) daily and Short-Form-36 (HRQOL domains) during the first and second appointment.


RESULTS
A significant, but weak association between the activity diary and Actical was present in patients with CFS (rs = 0.376 and rs = 0.352; p < 0.001) and a moderately strong association in healthy controls (rs = 0.605; and rs = 0.644; p < 0.001) between week and weekend days, respectively. A linear mixed model identified a negative association between age and the discrepancy between the self-reported and objective measure of PA in both patients with CFS and healthy controls.


CONCLUSION
The activity diary showed limited ability to register the PAL in female patients with CFS. The discrepancy between measures was not explained by illness-related complaints, HRQOL domains or demographic factors. The activity diary cannot replace objective activity monitoring measured with an accelerometer, but may provide additional information about the perceived activity.
['Vergauwen|Kuni|K|', 'Huijnen|Ivan P J|IPJ|', 'Smeets|Rob J E M|RJEM|', 'Kos|Daphne|D|', 'van Eupen|Inge|I|', 'Nijs|Jo|J|', 'Meeus|Mira|M|']
D061725:Accelerometry D000328:Adult D016022:Case-Control Studies D015444:Exercise D015673:Fatigue Syndrome, Chronic D005260:Female D006801:Humans D008875:Middle Aged D011788:Quality of Life D015203:Reproducibility of Results D057566:Self Report D055815:Young Adult
Physical activity Chronic fatigue syndrome Self-report Accelerometry Assessment Validity