By Diagnostics World News Staff
March 5, 2026 | At February’s Integrative Healthcare Symposium, Dr. George Schatz urged clinicians to rethink how they evaluate long COVID. For patients who still struggle with long-term fatigue, brain fog, palpitations, and sleep disruption, he proposed a diagnostics-first framework that prioritizes mechanism over labels.
Schatz, a physician at the Andrew Weil Center for Integrative Medicine, framed long COVID assessment as a pyramid. First, he advised ruling out significant pathology in lab work. In his practice, he looks for organ dysfunction, unmasked cardiometabolic disease, autoimmune conditions, and other comorbidities that could explain persistent symptoms. This initial triage, he said, prevents both over-treatment and missed diagnoses. Then, the foundation of basics: sleep, stress management, diet, and movement.
Once the foundation is established, Schatz identifies the most prevalent underlying mechanisms of long COVID. There are three phenotypes that stand out that are common but difficult to treat. The first one is Postural Orthostatic Tachycardia Syndrome (POTS). While tilt-table testing remains the formal diagnostic standard, Schatz often relies on bedside evaluation and history: marked heart rate spikes with standing, showering, or minimal exertion in a post-COVID patient with fatigue strongly suggest autonomic dysfunction. From there, he stratifies by subtype. In suspected hypovolemic POTS, he probes for thiamine deficiency, describing it as both a therapeutic and diagnostic lever. Clinical improvement after thiamine repletion—especially with more bioavailable forms—serves as functional confirmation that impaired glucose metabolism and brainstem-mediated autonomic control were central drivers.
The second phenotype is mast cell activation disorder. Schatz mentioned that this must be ruled out in long COVID patients because mast cell reactivity can prevent patients from tolerating other treatments. He described recognizing patterns, such as concurrent dermatologic (flushing, hives), respiratory (allergic-type symptoms), and gastrointestinal (IBS-like), that all together point toward mast cell involvement.
The most biochemically intricate layer of his framework centers on tryptophan metabolism dysregulation. While tryptophan is widely recognized as a serotonin precursor, Schatz noted that roughly 90% is metabolized through the kynurenine pathway toward NAD+ production. In long COVID, immune activation appears to upregulate indoleamine 2,3-dioxygenase (IDO) and tryptophan 2,3-dioxygenase (TDO), shunting metabolism toward quinolinic acid, a neurotoxic NMDA receptor agonist. The downstream effects—brain fog, depression, sleep disturbance, and profound fatigue—mirror the clinical presentation seen in many patients.
For Schatz, long COVID demands a shift from checklist medicine to a systems approach. In his model, accurate diagnosis is less about attaching more labels—and more about identifying the physiologic circuits that remain stuck in dysfunction long after the virus has cleared.