Face immersion reflex for diagnosis of diabetic cardiovascular autonomic neuropathy

To evaluate face immersion reflex (FIR) as a diagnostic test for diabetic autonomic neuropathy, we studied 15 patients with diabetic cardiovascular autonomic neuropathy--defined as the presence of at least two other abnormal autonomic tests-and 15 healthy subjects as a control group. All patients underwent six different autonomic tests including deep breathing R-R variation, Valsalva maneuver, heart rate and blood pressure response to standing, intravenous atropine injection and FIR. FIR test was considered positive for autonomic neuropathy if heart rate did not decrease at least 15% of the basal rate after 10 sec of immersion. FIR was positive in all the diabetic patients and negative in the 15 controls. Its sensitivity was higher than any other single autonomic test (p < 0.025). Considering two abnormal autonomic tests as a gold standard for diabetic cardiovascular autonomic neuropathy, sensitivity was 100% for FIR, 66% for deep breathing R-R variation and Valsalva maneuver, 53% for blood pressure (BP) response to standing and 20% for i.v. atropine injection. All the test were highly specific. We conclude FIR test should be considered among diagnostic tests for diabetic cardiovascular autonomic neuropathy.