Results from the Displace Consortium: Practice Patterns on the Use of Transcranial Doppler Screening for Risk of Stroke in Children with Sickle Cell Anemia
Authors: Phillips Shannon , Mueller Martina , Schlenz Alyssa M , Melvin Cathy , Adams Robert J. , Kanter Julie 
Published: October 2019

Abstract
Introduction: Stroke is one of the most devastating complications of sickle cell anemia (SCA). The STOP (Stroke Prevention Trial in Sickle Cell Anemia) protocol has been adopted by National Heart Lung and Blood Institute (NHLBI) as the guideline for stroke screening using transcranial Doppler ultrasound (TCD) and prevention with chronic red cell transfusion therapy (CRCT). Evidence from the STOP I/II studies indicates the protocol is highly effective, yet wide scale implementation has not been achieved. The DISPLACE (Dissemination and Implementation Looking at the Care Environment) project is a multicenter, NHLBI funded consortium of 28 sites across the United States whose purpose is to identify barriers to the implementation of the STOP protocol and test novel methods for overcoming barriers. The purpose of this study was to use data on practice patterns to evaluate current measurement and practice standards at DISPLACE consortia sites. This abstract presents reported TCD screening and CRCT practices.
Methods: A practice patterns survey was sent to the principal investigator (PI) for each DISPLACE site via RedCap ©. PIs were hematology/oncology specialty care providers for children with SCA. Sites represent urban and rural regions, large and small academic institutions, and community-based institutions. The survey was developed by the study investigators; questions were predominantly in a multiple-choice format. Items pertaining to TCD screening included: screening technique (including type of TCD); screening frequency; follow-up for abnormal, conditional, and inadequate results; standard value ranges.
Results: All 28 PIs completed the survey. About half of the respondents were female (53.5%). Most identified as White (77.8%), followed by Asian (11.1%) and Black or African American (7.4%). Two identified as Hispanic or Latino (7.4%). Slightly more sites reported using standard TCD (57.1%) versus imaging TCD (TCDi) (42.9%). To calculate the time-averaged mean of the maximum (TAMM) velocities and characterize TCD results, nearly all sites use the middle cerebral artery (96.4%); a majority also use the anterior cerebral artery and/or the terminal internal cerebral artery or distal internal cerebral artery (71.4%). Fewer sites use the posterior cerebral artery (35.7%) or the basilar artery (14.3%). In 7.1% of sites, the radiologist determines which vessels to use during the exam. TCD screening is ordered for children with SCA annually in 92.9% of sites and every 6 months in 7.1% of sites.
When TCD screening indicates abnormal TAMM velocities, 85.7% of sites initiate CRCT, 7.1% initiate hydroxyurea (HU) therapy, and 3.6% initiate both HU and CRCT. For additional evaluation, an MRI/MRA is obtained at 64.3% of sites. For high conditional results, the most common action is to initiate HU (67.9%). Other responses include obtaining an MRI/MRA (46.4%) and/or repeating the TCD in 2-4 weeks (25.0%), 6-8 weeks (35.7%), or 12-16 weeks (7.1%). Results deemed inadequate led to repeating the TCD in 2-12 weeks (57.1%) or in one year (3.6%), obtaining an MRI/MRA (57.1%), beginning HU therapy (7.1%), or no repeat TCD or change in management (3.6%). Actions for low conditional results include repeating the TCD (71.4%), obtaining an MRI/MRA (32.3%), and/or initiating HU therapy (57.1%).
Surprisingly, sites use different TAMM ranges to characterize the normal/abnormal findings (Table 1).
Conclusions: Nearly all DISPLACE sites order TCD screening annually, as recommended in the guidelines, with some ordering screening more frequently. A few sites did not report initiation of CRCT per STOP protocol for abnormal TCD results; however, over half of the sites reported following up with an MRI/MRA, which may suggest evaluating for vasculopathy prior to CRCT. Some sites reported beginning HU therapy for abnormal results; this may reflect consideration of patients for whom CRCT is not possible, but data were not collected for confirmation. Interestingly, results suggest a reliance on MRI/MRA since sites commonly reported ordering neuroradiology studies for abnormal, conditional, and inadequate TCD results. This may suggest an unclear pathway for children with borderline TCD results, and an area for future study. While reported value ranges closely approximated those in the STOP protocol, results indicate sites conducting screening with TCDi may use more conservative values than the validated protocol.

Disclosures
Phillips: NHLBI: Research Funding. Mueller:NHLBI: Research Funding. Schlenz:NHLBI: Research Funding. Melvin:NHLBI: Research Funding. Adams:NHLBI: Research Funding. Kanter:AstraZeneca: Membership on an entity's Board of Directors or advisory committees; bluebird bio: Membership on an entity's Board of Directors or advisory committees, Research Funding; Global Blood Therapeutics: Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Sancilio: Research Funding; NHLBI: Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Research Funding; Apopharma: Research Funding; ASH: Membership on an entity's Board of Directors or advisory committees.