Diagnostic Approach to Autonomic Neuropathy

Initial Assessment

The American Diabetes Association recommends screening for autonomic neuropathy in individuals who have had type 1 diabetes for ≥5 years and in all individuals with type 2 diabetes at diagnosis, with annual assessments thereafter 3
Symptoms to specifically inquire about include orthostatic intolerance, syncope or near-syncope episodes, exercise intolerance, gastrointestinal symptoms, urinary symptoms, sexual dysfunction, and sweating abnormalities in patients with diabetes 3

The American College of Cardiology recommends cardiovascular autonomic reflex tests (CARTs) as the gold standard for clinical diagnosis of autonomic neuropathy, which includes heart rate variability (HRV) testing, baroreflex sensitivity testing, and orthostatic hypotension assessment 5, 6, 7, 8
Diagnostic criteria for cardiovascular autonomic neuropathy (CAN) include early CAN (one abnormal heart rate test result), definite CAN (two or more abnormal heart rate test results), and severe CAN (presence of orthostatic hypotension along with abnormal heart rate tests) 5, 6

The American Gastroenterological Association recommends gastric emptying scintigraphy (4-hour test) as the diagnostic gold standard for suspected gastroparesis, with the 13C octanoic acid breath test as an approved alternative 3

Testing should be performed in a quiet environment with controlled temperature (21-23°C), and patients should fast for 3 hours before testing, avoid caffeine, alcohol, and smoking for at least 2 hours prior, and avoid strenuous physical exercise for 24 hours before testing 5, 6, 10

Age-related normal reference values are required for accurate interpretation, and confounding factors such as medications, respiratory or cardiovascular diseases, and resting heart rate >100 bpm should be considered 5, 6

Relying on a single test rather than a battery of validated tests, failing to consider age-related changes in autonomic function, not controlling for medications that can affect autonomic function, testing during periods of glycemic instability, and overlooking autonomic neuropathy in patients with small fiber neuropathy should be avoided 1, 5, 6, 8, 10