An earlier study by these researchers concluded that time frame, symptom stability, and momentary severity appear to influence reliability in reporting ME/CFS symptoms. These factors must be taken into account, because “[a]ccurate and reliable assessment is a crucial first step in understanding and treating this debilitating and often misunderstood illness.”

Research abstract:

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 time frames (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 Analyses were used to determine the optimal recall time frame (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 time frame in terms of test–retest reliability for stable symptoms was highly uniform, such that all Fukuda CFS symptoms were more reliably recalled at the six-month time frame.

Furthermore, the optimal time frame for CFS symptoms perceived as variable, differed across symptoms. Symptom stability and recall time frame are important to consider in order to improve the accuracy and reliability of the current methods for diagnosing this illness.

Public Interest Statement:

Chronic fatigue syndrome (CFS) is a debilitating illness and the cause is currently unknown. Developing an accurate and reliable way of diagnosing CFS remains a challenge for health professionals. Diagnosis typically requires patients’ self-report of their symptoms and there is little research on factors that influence symptom reporting.

This study is an investigation of whether symptom stability influences the reliability in which patients report their symptoms over time, and whether symptom stability can influence the optimal time frame for assessing symptoms on a questionnaire.

Findings revealed that when headaches were perceived as more stable, they were recalled more reliably. Furthermore, CFS symptoms that were rated as stable over time were recalled with greater reliability when using longer time frames (the past six months vs. past week). More research on factors that influence the accuracy and reliability of symptom reporting may lead to improvements in the way CFS is assessed and diagnosed.

The impact of symptom stability on time frame and recall reliability in CFS, by M Evans & LA Jason in Cogent Psychology (2015), 2: 1079945.