In Reply I concur with Drs Fink and Schröder that more research is needed to understand the etiology and refine the diagnosis of systemic exertion intolerance disease. I, however, cannot agree with their conclusion that the IOM Committee’s case definition fails because it was not based on a cluster or factor analysis or latent class analysis or by using similar statistical techniques.
The Committee examined the existing literature that used these techniques1(pp60-66) and found those studies inadequate for several reasons. The Committee also recognized that the framing of salient case definitions frequently relies on a variety of inputs, including expert consensus, input from patients and stakeholders, and evidence-based review of the literature that addresses etiology, pathophysiology, and discriminating clinical characteristics.
Clayton EW. Redefining Myalgic Encephalomyelitis/Chronic Fatigue Syndrome—Reply. JAMA. 2015;314(1):85-86. doi:10.1001/jama.2015.5760