Chronic fatigue syndrome (CFS) is a disorder characterized by debilitating fatigue whose etiology and pathophysiology remain unclear. Previous studies showed abnormalities of the RNase L pathway in peripheral blood mononuclear cells (PBMC) from patients with CFS (1, 2). The ratio of RNase L isoforms (37 kDa/83 kDa ratio [37/83 R]) has therefore been proposed as a potential biochemical marker of CFS, with a sensitivity of 91% and a specificity of 71% when the cutoff ratio was 0.4 (3).
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Source: Tiev KP, Briant M, Ziani M, Cabane J, Demettre E, Lebleu B. Variability of the RNase L isoform ratio (37 kiloDaltons/83 kiloDaltons) in diagnosis of chronic fatigue syndrome. Clin Diagn Lab Immunol. 2005 Feb;12(2):366. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC549313/ (Full article)