Transcranial Doppler (TCD) screening for stroke prevention in sickle cell anemia: pitfalls in technique variation

Background. The Stroke Prevention Trial in Sickle Cell Anemia (STOP) identi fied children as being at high stroke risk if the time-averaged maximum mea n velocity (TAMMV) of the middle cerebral or intracranial internal carotid arteries measured greater than or equal to 200 cm/s. These values were obta ined utilizing a 2-mHz dedicated nonimaging pulsed Doppler technique (TCD) and manual measurements. Questions have been raised as to the comparability of results obtained with different ultrasound machines and measurement tec hniques. Objective. The purpose of this study was to compare nonimaging (TCD) and tr anscranial duplex imaging (TCDI) findings in children potentially at risk f or stroke with sickle cell disease. Materials and methods. Twenty-two children with sickle cell disease and no history of stroke were evaluated by both TCD and; TCDI. Examinations were p erformed on the same day without knowledge of the other modality results an d read independently using manually obtained measurements. Mean velocities, peak systolic velocities, and end diastolic velocities obtained by the two techniques were compared. In a subgroup, manual measurements were compared to electronically obtained measurements. Results. TCDI values were lower than TCD measurements for all vessels. TCDI TAMMV values were most similar to the TCD values in the middle cerebral ar tery (-9.0 %) and distal internal cerebral artery (-10.8 %), with greater v ariability in the anterior cerebral artery (-19.3 %), bifurcation (-16.3 %) , and basilar arteries (-23.1%). Risk group placement based on middle cereb ral artery TAMMV values did not change when comparing the two techniques. M easurements obtained electronically were lower than those obtained manually . Conclusion. Velocities obtained by TCDI may be lower than TCD measurements, and these differences should be taken into consideration when performing s creening for stroke risk and selection for prophylactic transfusion based o n the STOP protocol.