Table 3 

Receiveroperator characteristic curve analysis of heart rate variability indexes 

AUC (95% CI) 
Pvalue^{a} 
Best cutoff value 
Distance to optimum value (0,1) 



24hour 



Mean NN (ms) 
0.61 (0.45  0.79) 
0.18 
779 
0.53 
SDNN (ms) 
0.67 (0.50  0.83) 
0.05 
141 
0.45 
SDANN (ms) 
0.64 (0.48  0.81) 
0.11 
119 
0.48 
SDSD (ms) 
0.69 (0.53  0.84) 
0.03 
40 
0.48 
RMSSD (ms) 
0.69 (0.53  0.84) 
0.03 
40 
0.48 
pNN50 (%) 
0.68 (0.52  0.83) 
0.04 
13 
0.53 


Sleeping hours 



Mean NN (ms) 
0.59 (0.41  0.77) 
0.30 
922 
0.49 
SDNN (ms) 
0.79 (0.66  0.92) 
0.00 
114 
0.35 
SDANN (ms) 
0.75 (0.60  0.897) 
0.00 
59 
0.37 
SDSD (ms) 
0.64 (0.48  0.81) 
0.09 
44 
0.53 
RMSSD (ms) 
0.64 (0.48  0.81) 
0.09 
44 
0.53 
pNN50 (%) 
0.63 (0.47  0.80) 
0.13 
31 
0.55 


^{a}Null hypothesis is that area under the curve = 0.5. Holter recordings were analyzed for 24 hours, and during sleeping time (from 00.00 to 06.00 hours). AUC, area under the curve; CI, confidence interval; Mean NN, mean NN interval; SDNN, standard deviation of the NN intervals; SDANN, mean standard deviation of the average NN intervals calculated over 5 minutes; ms, milliseconds; SDSD, standard deviation of the successive NN differences; RMSSD, square root of the mean of the squares of differences between adjacent NN intervals; pNN50, percentage of adjacent pairs of RR intervals that differ by more than 50 ms from each other in a given time period. 

Lerma et al. Arthritis Research & Therapy 2011 13:R185 doi:10.1186/ar3513 