ABSTRACT
Long COVID patients present a cluster of symptoms that overlaps with other post-infectious conditions, such as patients diagnosed with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Besides fatigue, one of the most limiting clinical manifestations in ME/CFS is post-exertional malaise (PEM), which Long COVID patients also report. Therefore, there are concerns about treatment approaches in rehabilitation for long COVID patients. Up to date, Long COVID patients present fatigue and respiratory symptoms predominantly. The hypothesis presented in this paper is that the treatment approach for Long COVID patients may depend on the aetiology of their symptoms, which objective tests can assess. And the primary affected system in a given patient may determine the individual response to physical exhaustion. Then, we propose an assessment to confirm the system impaired under the predominant symptom to guide the rehabilitation intervention. Fatigue-related symptoms, PEM, physical deconditioning and response to exertion should be assessed in Long COVID patients with predominant fatigue. In contrast, the respiratory function by spirometry and the diffusion capacity should be objectively assessed in those patients with predominantly respiratory symptoms. Future research should develop and validate patient-reported outcomes or cardiopulmonary exercise testing to objectively assess the symptoms and functional status in Long COVID patients to reinforce the proposed assessment.