Diabetic medicine : a journal of the British Diabetic Association
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To establish normal ranges for assessment of autonomic dysfunction, a battery of cardiovascular reflex tests was performed in 120 healthy subjects aged 15-67 years using a computer-based technique. Tests of heart rate variation (HRV) included 8 measures at rest: coefficient of variation (CV), root mean squared successive difference (RMSSD), spectral analysis of HRV in the low frequency, mid frequency, and high frequency bands in the supine and standing postures; 5 measures during deep breathing: CVb, RMSSDb, Expiration-Inspiration (E-I) difference, E/I ratio, and mean circular resultant of vector analysis; Valsalva ratio, and max/min 30:15 ratio. In addition, the change in systolic and diastolic blood pressure in response to standing and the diastolic blood pressure response to sustained handgrip were determined. ⋯ The results of these tests had to be analysed using a log(y-1) transformation. The intra-individual reproducibility determined on two consecutive days in 20 healthy subjects and 21 diabetic patients indicated that there were no major differences between the two groups regarding the day-to-day variation of test results, which was highest for the Valsalva ratio. We conclude that: (1) all indices of spectral and vector analyses of HRV are age-dependent and have the advantage of being independent of heart rate; (2) RMSSD, E-I difference, and the 30:15 ratio as it was used previously are not suitable for evaluation of autonomic dysfunction in diabetes; (3) log(y-1) transformation is required to determine age-dependent normal ranges and reproducibility for the three ratios.