Abstract
About 11% of SS patients will have a first stroke by age 18–20 years. Abnormal high velocities are associated with a high risk of stroke, which can be significantly reduced by a long-term transfusion program. The stroke rate in Californian SCD children has declined since the advent of transcranial doppler (TCD), but there are no reports on the outcome of patients screened from birth by TCD.
Since 1992, TCD has been systematically performed from the age of 12–18 months in the Creteil cohort. MRI/MRA was performed annually after the age of 5 years, or earlier in case of abnormal TCD. Patients with abn. high velocities (TAMMX >= 200 cm/s) were offered transfusion regimens for stroke prevention, but hydroxyurea was proposed secondarily to patients who had normal MRA findings and whose velocities normalized (< 170 cm/s). TCD was performed every three months in these patients, and a transfusion program was resumed if the findings were again abnormal. We report the cerebrovascular outcome of patients born after 1988 who were regularly followed in our center and screened by TCD.
This cohort consisted of 242 SCD patients (178 SS, 9 Sb0, 41 SC, and 14 Sb+). Mean follow-up was 6.2 y (range 0.1–17.8), representing 1498 patient-years overall and 1139 patient-years in the SS/Sb0 population. Alpha gene deletion was present in 41% of patients (71/175). The beta genotype was available in 165 patients, and was homozygous Bantou (n=56, 34%), Senegal (n=9, 5.5%), Benin (n=35, 21.2%), or "other" (n=65, 39.4%). Four deaths occurred, all involving SS patients, at 1.2 y (enteritis in 1995), 1.8 y (trip to Africa in 2003), 1.9 y (pneumo. meningitis in 1997) and 3.7 y (ACS and curare allergy in 1998). The mortality rate was 0.27 per 100 patient-years overall and 0.35 in SS/Sb0 patients. The Kaplan-Meier (KM) estimate of the risk of abn. velocities (> 200 cm/s) was 15.7% at 5 y and 22.7% at 10 y of age in SS/Sb0 patients. No SC/Sb+ patients had abn. velocities. Strokes occurred in only two SS patients: the first patient had abn. high velocities detected at the age of 1.5 years and had a stroke at the age of 1.6 years, just before the TCD control and initiation of the transfusion program. The second patient had normal left-sided velocities but no available temporal window on the right side after the age of 1.4 y; this patient had a stroke at age 4.4 y. These observations prompted us to begin TP after the first abn. TCD and to perform MRI/MRA when no window was available. The rates of stroke were 0.13 per 100 patient-years overall, and and 0.18 per 100 patients-years in SS/Sb0 patients. The KM estimate of the risk of stroke was 1.02% at 5 y and 18 y of age in SS/Sb0 patients. KM estimates of the risk of ischemic lesions at 5 and 10 y were respectively 6.4% and 17.7% in SS/Sb0 patients with normal TCD and 20.9% and 43.5% in patients with a history of abn. TCD (Log Rank test 0.0035).
This single-center study shows that a strategy based on early and regular TCD can efficiently prevent stroke in a newborn screened cohort: the rate of stroke and the KM risk of stroke were far lower than recently reported (Quinn CT Blood 2004). However, the risk of ischemic lesions remained high particularly in patients with a history of abn. velocities. Abn. TCD velocities identify a high-risk group who may qualify for matched related donor stem cell transplantation.
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