Nocturnal heart rate variability parameters as potential fibromyalgia biomarker: correlation with symptoms severity

Table 4 Predictive value of heart rate variability indexes in 22 patients with fibromyalgia and 22 controls.

	Sensitivity (%)	Specificity (%)	PPV (%)	NPV (%)
24-hour
Mean NN ≤ 779 ms	73	55	62	67
SDNN ≤ 141 ms	68	68	68	68
SDANN ≤ 119 ms	64	68	67	65
SDSD ≤ 40 ms	64	68	67	65
RMSSD ≤ 40 ms	64	68	67	65
pNN50 ≤ 13%	55	73	67	62
Sleeping hours
Mean NN ≤ 922 ms	73	59	64	68
SDNN ≤ 114 ms	86	68	73	83
SDANN ≤ 59 ms	68	82	79	72
SDSD ≤ 44 ms	55	73	67	62
RMSSD ≤ 44 ms	55	73	67	62
pNN50 ≤ 31%	68	55	60	63

Mean NN, mean NN interval; pNN50, percentage of adjacent pairs of R-R intervals that differ by more than 50 ms from each other in a given time period; ms, milliseconds; RMSSD, square root of the mean of the squares of differences between adjacent NN intervals; SDANN, mean standard deviation of the average NN intervals calculated over 5 minutes; SDNN, standard deviation of the NN intervals; SDSD, standard deviation of the successive NN differences.