Table I.

Population characteristics: total and by initial ACS age grouping

Characteristic	Total Population*	Initial ACS <4 years (n = 56)	Initial ACS ≥4 years (n = 69)	P Value§
Age	5.78 (3.85) (Range: 1.02 - 17.67)
Male (%)	55.2	67.9	44.9	0.010
Time followed from age 1	14.07 (4.46)	13.16 (4.33)	14.82 (4.45)	0.038
Asthma diagnosis (%)	34.4	41.1	29.0	0.157
Mother has asthma (%) n=120	13.3	15.1	11.9	0.614
Hemoglobin	8.23 (1.17)	8.12 (1.06)	8.32 (1.25)	0.338
White blood cell count	11.94 (3.98)	12.78 (4.50)	11.25 (3.38)	0.033
Reticulocyte	11.31 (5.44)	10.41 (4.49)	12.04 (6.04)	0.095
Log Ige (n=118)	4.07 (1.57)	4.13 (1.67)	4.02 (1.49)	0.701
ACS or pain recurrence (%)
ACS recurrence after first ACS n (%)	93 (74.4)	47 (83.9)	46 (66.7)	0.028
Pain after first ACS n (%)	99 (79.2)	46 (82.1)	53 (76.8)	0.465
ACS rate per year after first ACS, mean [median] (std. dev.)	0.29 [0.19] (0.25)	0.40 [0.32] (0.29)	0.20 [0.14] (0.17)	<0.001
Pain rate per year after first ACS, mean [median] (std. dev.)	0.65 [0.42] (0.82)	0.67 [0.48] (0.80)	0.64 [0.32] (0.84)	0.415
ACS and pain rate per year after first ACS, mean [median] (std. dev.)	0.94 [0.70] (0.88)	1.07 [0.88] (0.87)	0.84 [0.59] (0.88)	0.011#

^*Mean (std. dev.) unless otherwise noted

^§Chi-square test for categorical variables; t test for continuous variables

^#Mann-Whitney U test