Diabetes Care, Vol 17, Issue 12 1433-1440, Copyright © 1994 by American Diabetes Association
Reliability and validity of cardiovascular and vasomotor autonomic function tests
MS Hartwig, SS Cardoso, DK Hathaway and AO Gaber
Department of Nursing, College of Nursing and Health Professions, Arkansas State University, Jonesboro.
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.