Table 1.

Demographics of the cohort of children with normal transcranial Doppler (TCD) measurements (time averaged mean maximum velocity of < 200 cm/second, non-imaging or < 185 cm/second imaging technique) stratified by negative or positive MRI (n=421)

Variable*	Normal TCD measurements, no evidence of silent cerebral infarct MRI (n=353)	Normal TCD measurements, evidence of silent cerebral infarct (n=68)	P Value*
Age at registration	8.9 (2.4)	9.1 (2.6)	0.437
Sex, Male (%)	49.6	54.4	0.465
Systolic blood pressure (n=416)	107.5 (11.8)	110.6 (10.5)	0.044
Steady state hemoglobin	8.3 (1.2)	7.9 (1.0)	0.006
Reticulocytes (%) (n=418)	11.6 (5.6)	14.3 (6.3)	<0.001
Hydroxyurea use before end of follow-up (%)	25.2	23.5	0.769
Chronic transfusion before end of follow-up (%)	4.8	7.4	0.375#
Follow-up time until event, end-of study, or chronic transfusion, years	3.6 (1.3)	3.4 (1.5)	0.270
New neurological event (stroke, seizure or TIA) (%)	1.7	5.9	0.061#
Incidence rate, new neurological events (events/100 patient-years), 95% confidence interval	0.47 (0.17 – 1.02)	1.71 (0.46 – 4.37)	0.065§

^*Mean and standard deviation or chi-square test unless otherwise noted

^#Fisher’s exact test

^§Mid-p exact test