Editor's Comment: Meredyth Evans wrote her Master's thesis on the reliability of questionnaires for patients with ME/CFS, specifically addressing how this method is applied in the "empirical" case definition for diagnosing the illness. The empirical case definition expands the Fukuda case definition by including questionnaires as assessment tools. As Evans discussed in her thesis, a person's recall of the severity of symptoms she or he has experienced is influenced by a variety of factors, including whether the symptoms have been consistent.
Although this study does not rule out the validity of questionnaires for supporting a case definition, it does examine some of the pitfalls of using time frames to assess symptoms. Evans discovered that the more stable a symptom was, the easier it was to remember. Waxing and waning symptoms are one of the key features of this illness, especially during acute phases, which means patients might have greater problems with recall if they are in relapse. However, two of the Fukuda definition symptoms that Evans explored - sore throat and cognitive problems - did not fit into this model. "It is possible," she says, "that this impact on reliability is due to the fact that people are having difficulty concentrating on what the question is asking them; thus having difficulty reliably recalling their concentration problems..."
Evans concluded that time frame, symptom stability, and momentary severity do 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."
To read the full text of "Effects of Time Frame on the Recall Reliability of CFS Symptoms" click HERE.
By M. Evans and L.A. Jason
This study serves as an investigation of the reliability of symptom data as reported by individuals with chronic fatigue syndrome (CFS), across three recall time frames (the past week, the past month, and the past 6 months), and at two assessment points (with 1 week in between each assessment). Multilevel model analyses were used to determine the optimal recall time frame, in terms of test -retest reliability, for each of the Fukuda et al. (1994) case defining symptoms.
Results suggested that the optimal time frame for reliably reporting CFS symptoms was six months for sore throat, lymph node pain, muscle pain, post-exertional malaise, headaches, memory/concentration difficulties, and unrefreshing sleep. For joint pain, the optimal time frame was one month.
Researchers who are interested in the assessment of CFS symptoms need to take recall time frame into account, especially when the intended goal is to standardize and improve the methods used to reliably and accurately diagnose this complex illness.
Source: Eval Health Prof. 2013 Sep 23. [Epub ahead of print]. Evans M, Jason LA.