The impact of symptom stability on time frame and recall reliability in CFS

This study is an investigation of the potential impact of perceived symptom stability on the recall reliability of symptom severity and frequency as reported by individuals with chronic fatigue syndrome (CFS). Symptoms were recalled using three different recall timeframes (the past week, the past month, and the past six months) and at two assessment points (with one week in between each assessment).

Participants were 51 adults (45 women and 6 men), between the ages of 29 and 66 with a current diagnosis of CFS. Multilevel Model (MLM) Analyses were used to determine the optimal recall timeframe (in terms of test-retest reliability) for reporting symptoms perceived as variable and as stable over time.

Headaches were recalled more reliably when they were reported as stable over time. Furthermore, the optimal timeframe in terms of test-retest reliability for stable symptoms was highly uniform, such that all Fukuda¹ CFS symptoms were more reliably recalled at the six month timeframe. Furthermore, the optimal timeframe for CFS symptoms perceived as variable, differed across symptoms.

Symptom stability and recall timeframe are important to consider in order to improve the accuracy and reliability of the current methods for diagnosing this illness.