Problems in Defining Post-Exertional Malaise

Post-exertional malaise (PEM) is a cardinal symptom of the illnesses referred to as Myalgic Encephalomyelitis (ME), Myalgic Encephalomyelitis/chronic fatigue syndrome (ME/CFS), and chronic fatigue syndrome (CFS). PEM is reported to occur in many of these patients, and with several criteria (e.g., ME and ME/CFS), this symptom is mandatory (Carruthers etal., 2003 Carruthers, B. M., Jain, A. K., De Meirleir, K. L., Peterson, D. L., Klimas, N. G., Lerner, A. M., … van de Sande, M. I. (2003). Myalgic encephalomyelitis/chronic fatigue syndrome: Clinical working case definition, diagnostic and treatments protocols. Journal of Chronic Fatigue Syndrome, 11, 7–115.[Taylor & Francis Online] , [Google Scholar], 2011 Carruthers, B. M., van de Sande, M. I., De Meirleir, K. L., Klimas, N. G., Broderick, G., Mitchell, T., … Stevens, S. (2011). Myalgic encephalomyelitis: International consensus criteria. Journal of Internal Medicine, 270, 327–338.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]). In the present study, 32 participants diagnosed with CFS (Fukuda etal., 1994 Fukuda, K., Straus, S. E., Hickie, I., Sharpe, M. C., Dobbins, J. G., & Komaroff, A. (1994). The chronic fatigue syndrome: A comprehensive approach to its definition and study. Annals of Internal Medicine, 121, 953–959. Retrieved from http://www.ncf-net.org/patents/pdf/Fukuda_Definition.pdf[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]) were examined on their responses to self-report items that were developed to capture the characteristics and patterns of PEM. As shown in the results, the slight differences in wording for various items may affect whether one is determined to have PEM according to currently used self-report criteria to assess CFS. Better understanding of how this symptom is assessed might help improve the diagnostic reliability and validity of ME, ME/CFS, and CFS.