From the Guidelines

No, electron transport chain testing is not a standard part of the workup for Chronic Fatigue Syndrome (CFS) (Myalgic Encephalomyelitis (ME)) 1.

The diagnosis of ME/CFS is based on clinical criteria, including a substantial reduction in the ability to engage in pre-illness levels of activities, profound fatigue, postexertional malaise, unrefreshing sleep, and cognitive impairment or orthostatic intolerance 1.
While mitochondrial dysfunction is a consistent abnormal finding in ME/CFS, electron transport chain testing is not specifically mentioned as a diagnostic tool 1.
The workup for ME/CFS typically involves a comprehensive medical history, physical examination, and laboratory tests to rule out other conditions that may be causing the symptoms 1.

Mitochondrial dysfunction, including diminished natural killer cell function, T cell exhaustion, and other T cell abnormalities, has been observed in ME/CFS 1.
Vascular and endothelial abnormalities, including deformed red blood cells and reduced blood volume, have also been found in ME/CFS 1.
However, electron transport chain testing is not a standard test used to diagnose or monitor ME/CFS 1.

From the Research

Electron transport chain testing is not a standard part of the workup for CFS/ME, but research suggests that mitochondrial dysfunction may play a role in the disease 2, 3, 4.
Studies have investigated mitochondrial function and electron transport chain activity in CFS/ME patients, with some finding abnormalities in mitochondrial function and structure 2, 3.
One study found that CFS/ME patients could be distinguished from non-fatigued patients through electron transport chain gene analysis, specifically reduced expression of ND4 and CyB and increased expression of Cox7C 4.
Another study used single-cell Raman micro-spectroscopy to examine mitochondrial function in CFS/ME patients and found that Raman bands associated with phenylalanine were significantly higher in CFS/ME patients than in healthy controls, suggesting a potential biomarker for the disease 3.

The diagnosis of CFS/ME is complex and often challenging, with many patients experiencing unmet health care needs and delayed diagnosis 5.
The management of CFS/ME is supportive and symptomatic, with a patient-centered care approach that focuses on pacing activities and strategic rest periods to manage post-exertional fatigue and malaise 5.
Research suggests that CFS/ME is a complex, chronic medical condition characterized by symptom clusters that include pathological fatigue, cognitive dysfunction, immune dysfunction, and autonomic dysfunction, among others 5.

While research suggests that mitochondrial dysfunction may play a role in CFS/ME, more studies are needed to fully understand the relationship between mitochondrial function and the disease 2, 3, 4.
Further research is also needed to develop effective diagnostic biomarkers and treatments for CFS/ME, as well as to improve patient outcomes and quality of life 5.