Why do some ME/CFS patients benefit from treatment with sodium dichloroacetate, but others do not?

Myalgic Encephalopathy/Chronic Fatigue Syndrome (ME/CFS) is an enigmatic disease the pathogenesis of which remains elusive. Pragmatic proof-of-principle of the hypothetical mechanisms causing the clinical symptoms has been delivered, but it is hard to explain why some patients do respond favourably to treatment with sodium dichloroacetate (DCA), which enhances the activity of the mitochondrial enzyme pyruvate dehydrogenase, but other patients experience no benefit from this substance. In a prospective trial including 35 ME/CFS patients, logistic regression analysis with stepwise elimination has identified 6 pre-treatment characteristics allowing for the differentiation between responders (n = 13) and non-reponders (n = 22) with high accuracy (P < 0.0001; area under the ROC-curve = 0.92). A formula was derived generating the probability of belonging to the group of responders. This finding may assist in selecting ME/CFS patients suitable for treatment with DCA, but requires further studies as to the predictive capacity of the derived formula.