Effects of Timeframe on the Recall Reliability of ME/CFS Symptoms

This study served as an investigation of the effects of symptom stability, timeframe length, and momentary symptom severity on the recall reliability of symptoms experienced by individuals with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). ME/CFS symptoms were assessed at four recall timeframes (right now, the past week, the past month, and the past six months) and at two assessment points. Analyses revealed that test-retest reliability was significantly stronger for recall of post-exertlonal malaise (PEM), headaches, and memory problems, when these symptoms were perceived to be stable over time rather than variable. It was also revealed that the optimal timeframe for variable ME/CFS symptoms differed across symptoms. Momentary symptom severity impacted recall reliability for two symptoms (sore throats and concentration problems) and only when the recall timeframe was six months. In general, analyses revealed that the optimal timeframe for reliably reporting stable ME/CFS symptoms is highly uniform, such that each of the symptoms measured were more reliably recalled at the six month timeframe. Furthermore, when symptom stability and momentary severity were removed from the analyses, individuals were most reliable in reporting the majority of their symptoms over a six month timeframe. This study provides evidence that timeframe, symptom stability, and momentary severity can influence the recall reliability of reporting ME/CFS symptoms. Furthermore, results showed that individuals with this illness are capable of reliably recalling their symptoms over longer timeframes than might be expected. An increased awareness and understanding of the impact that these contextual factors on recall reliability of ME/CFS symptoms would likely improve the way in which this complex illness is understood, diagnosed, and treated