Key result
Autonomic function tests, particularly percent vasoconstriction (reproducibility r = 0.90), were found to be reliable and valid clinical tools for detecting diabetic autonomic neuropathy.
Why the study?
Are cardiovascular and vasomotor autonomic function tests reliable and valid for detecting diabetic autonomic neuropathy in patients with IDDM?
Observational (n=42)
Are cardiovascular and vasomotor autonomic function tests reliable and valid for detecting diabetic autonomic neuropathy in patients with IDDM?
Effect estimate: r = 0.90
Cardiovascular and vasomotor autonomic function tests, particularly percent vasoconstriction, are reliable and valid tools for detecting diabetic autonomic neuropathy without requiring patient exertion.
Supports autonomic tests for diabetic neuropathy detection in IDDM; leaves open prospective outcome validation before routine use.
OBJECTIVE: To determine the reliability and validity of autonomic function tests (AFTs) as clinical tools for diagnosing diabetic autonomic dysfunction. RESEARCH DESIGN AND METHODS: Twenty-one healthy control subjects and 21 insulin-dependent diabetes mellitus (IDDM) patients (11 with no symptomatology and 10 with symptomatic diabetic autonomic neuropathy [DAN]) were matched for age, and administered three standard cardiovascular tests and two new vasomotor tests of autonomic function. Each of the cardiovascular tests (change in heart rate [delta bpm], Valsalva ratio [VR], change in systolic blood pressure [delta sBP]) and vasomotor tests (total pulse amplitude [TPA] and percent vasoconstriction [%VC]) were repeated within 1 week. Infrared photoplethysmography measured sympathetic-mediated vasomotor function. Reliability was determined by intraclass correlation coefficients. Validity was determined by analysis of variance procedures to test for differences between known groups and by computing sensitivity, specificity, and positive and negative predictive values. RESULTS: All AFTs were reliable, with %VC having highest reproducibility (r = 0.90). AFT scores were not different from time 1 to time 2. After controlling for age, two cardiovascular tests had significantly different values for control subjects and asymptomatic diabetic patients. AFTs, except delta sBP, were significantly different between symptomatic diabetic patients and asymptomatic diabetic patients after controlling for age and duration of disease simultaneously. Sensitivity, specificity, and predictive values for %VC were comparable to the values for delta bpm and VR. TPA indexes were lower but clinically acceptable. CONCLUSIONS: AFTs were found to be reliable and valid tests for detecting DAN. TPA and %VC are important because they measure an aspect of sympathetic function not assessed by standard cardiovascular AFTs, and they do not depend on the patient's cooperation or ability to exert effort.
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Hartwig et al. (1994) conducted an observational in Diabetic autonomic neuropathy (n=42). Autonomic function tests (cardiovascular and vasomotor) vs. Healthy controls and asymptomatic diabetic patients was evaluated on Reliability (intraclass correlation coefficients) and validity of autonomic function tests (r = 0.90). Autonomic function tests, particularly percent vasoconstriction (reproducibility r = 0.90), were found to be reliable and valid clinical tools for detecting diabetic autonomic neuropathy.
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