Multicenter prospective study of children with sickle cell disease: Radiographic and psychometric correlation

After obtaining familial informed consent, between January 1996 and July 19 97, 173 children (5 to 16 years old) with sickle cell disease were enrolled in a prospective multicenter study using blood screening, transcranial Dop pler ultrasonography (n = 143), cerebral magnetic resonance imaging (n = 14 4), and neuropsychologic performance evaluation (n = 156) (Wechsler Intelli gence tests WISC-III, WIPPSI-R), which were also performed in 76 sibling co ntrols (5 to 15 years old). Among the 173 patients with sickle cell disease (155 homozygous for hemoglobin SS, 8 sickle cell beta(0) thalassemia, 3 si ckle cell beta(+) thalassemia, 7 sickle cell hemoglobin C disease SC), 12 ( 6.9%) had a history of overt stroke, and the incidence of abnormal transcra nial Doppler ultrasonography (defined as mean middle cerebral artery veloci ty > 200 cm/sec or absent) was 8.4% in the overall study population and 9.6 % in patients with homozygous sickle cell anemia. The silent stroke rate wa s 15%. Significantly impaired cognitive functioning was observed in sickle cell disease patients with a history of stroke (Performance IQ and Full Sca le IQ), but also in patients with silent strokes (Similarities, Vocabulary, and Verbal Comprehension). However, infarcts on magnetic resonance imaging were not the only factors of cognitive deficit: Verbal IQ, Performance IQ, and Full Scale IQ were strongly impaired in patients with severe chronic a nemia (hematocrit less than or equal to 20%) and in those with thrombocytos is (platelets > 500 X 10(9)/L). Multivariate logistic regression analysis s howed that abnormal magnetic resonance imaging (odds ratio [OR] = 2.76) (P = .047), hematocrit less than or equal to 20% (OR = 5.85) (P = .005), and p latelets > 500 X 10(9)/L(OR = 3.99) (P = .004) were independent factors of cognitive deficiency (Full Scale IQ < 75) in sickle cell disease patients. The unfavorable effect of low hematocrit has already been suggested, but th is is the first report concerning an effect of thrombocytosis and showing t hat silent stroke alone is not a factor of cognitive deficit when not assoc iated with low hematocrit or thrombocytosis. The effect of hydroxyurea, whi ch is known to increase hematocrit and decrease platelet count, on cognitiv e functioning of sickle cell patients should be evaluated prospectively.