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) identified children as being at high stroke risk if the time-averaged maximum mean velocity (TAMMV) of the middle cerebral or intracranial internal carotid arteries measured > or = 200 cm/s. These values were obtained 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 techniques.

OBJECTIVE: The purpose of this study was to compare nonimaging (TCD) and transcranial duplex imaging (TCDI) findings in children potentially at risk for 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 performed on the same day without knowledge of the other modality results and 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 artery (-9.0%) and distal internal cerebral artery (-10.8%), with greater variability in the anterior cerebral artery (-19.3%), bifurcation (-16.3%), and basilar arteries (-23.1%). Risk group placement based on middle cerebral artery TAMMV values did not change when comparing the two techniques. Measurements 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 screening for stroke risk and selection for prophylactic transfusion based on the STOP protocol.