Table 4.

Receiver operating characteristic curve analysis

Phenotype	Age at first TTP episode requiring FFP < 18 y	Annual rate of TTP episodes > 1	Regular FFP prophylaxis
ADAMTS13 activity cutoff, %	< 2.74	< 1.61	< 2.74
Area under the curve (95% CI)	0.880 (0.746-1.013)	0.930 (0.829-1.032)	0.752 (0.564-0.941)
P	.001	.003	.023
Sensitivity	92.3%	78.3%	70.6%
Specificity	81.3%	100%	75.0%
OR (95% CI)	52.00 (4.74-570.53)	1.615 × 109 (NC)	7.20 (1.35-38.33)

OR indicates odds ratio; and NC, noncalculable.