title: Reliability of heart rate variability in patients with type 2 diabetes mellitus.
abstract: OBJECTIVE
  Heart rate variability may be used to assess diabetic cardiac autonomic neuropathy. The aim of the present study was to determine the reliability of standard short-term clinical measurements of heart rate variability in patients with Type 2 diabetes.
  
  
  METHODS
  In 24 patients with Type 2 diabetes (11 male, age 61 ± 9 years), parameters of heart rate variability in the time domain (standard deviation of RR intervals, coefficient of variation of RR intervals and root mean square of successive RR interval differences) and frequency domain (very low frequency, low frequency, high frequency and total spectral power) were derived from a 5-min electrocardiograph recorded during two laboratory visits separated by 16 ± 8 days. Absolute and relative reliability were assessed by 95% limits of random variation and the intraclass correlation coefficient, respectively. Categorical agreement of classifications of heart rate variability and sample size estimates for clinical trials were calculated.
  
  
  RESULTS
  Despite no significant difference in mean heart rate variability between tests, 95% limits of random variation indicated that repeated measurements were between 58% higher/37% lower (most reliable parameter; coefficient of variation of RR intervals) and 443% higher/82% lower (least reliable parameter; very low frequency power) than the first measure. The intraclass correlation coefficient ranged from 0.58 to 0.90 and sample size requirements from 20 to 93 patients per group. Agreement of categories of heart rate variability ranged from 79 to 96%.
  
  
  CONCLUSIONS
  Short-term clinical measurements of heart rate variability in patients with Type 2 diabetes are characterized by poor absolute reliability, but substantial to good relative reliability, suggesting greater clinical utility in diagnosis than in sequential follow-up.
authors.affiliation: School of Medicine, The University of Queensland, Brisbane, Qld, Australia. j.sacre@uq.edu.au
authors.forename: J W
authors.initials: JW
authors.lastname: Sacre
authors.forename: C L
authors.initials: CL
authors.lastname: Jellis
authors.forename: T H
authors.initials: TH
authors.lastname: Marwick
authors.forename: J S
authors.initials: JS
authors.lastname: Coombes
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D003627:Data Interpretation, Statistical; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000150:complications / Q000503:physiopathology*; D003929:Diabetic Neuropathies / Q000097:blood / Q000209:etiology / Q000503:physiopathology*; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D013997:Time Factors