Prevalence of abnormal or conditional TCDs in London and practicalities of setting up a TCD service

Tompeter, S., Aimiuwu, E., Kirkham, F. J. and Robins, A. (2008) Prevalence of abnormal or conditional TCDs in London and practicalities of setting up a TCD service. 13th Congress of the European Hematology Association, Copenhagen, Denmark. 11 - 14 Jun 2008.

Abstract

?Background and Aims. In sickle cell anaemia (SCA), internal carotid/middle cerebral artery velocities of >200 cm/sec (abnormal) and 170-199 cm/sec (conditional) on transcranial Doppler Ultrasound (TCD) predict stroke risks of 40% and 7% over the next 40 months respectively. The prevalence of abnormal and conditional TCD was around 8-10% in the 1990s but there is little recent data. There are a variety of different screening programs in London using imaging (South) and non-imaging (North) TCD. Some hospitals run regular Saturday services to improve attendance and decrease time spent off school. Others feel compliance is best achieved by having a second room in a normal clinic so patients have only one appointment to keep. Some use ultrasonographers, others radiologists and some haematologists. In view of the recently published UK Standards we undertook to screen the paediatric sickle cell population at the Whittington Hospital NHS Trust in North London, a haemoglobinopathy centre. The purposes of the sessions were to i) screen the population with TCD and compare the current prevalence with previous data ii) ascertain the important factors in setting up such a service and iii) determine whether birth factors increased risk for abnormal TCD. Methods. Patients were selected according to the following criteria: age >2 <20 and HbSS. HBSC and HbSBthal patients were screened if there were concerns regarding their neurology or if they had a sibling with HbSS attending. All patients were contacted by telephone. All appointments were during normal clinic times and 3 of the four sessions were during school times. Most patients did not have a simultaneous follow-up appointment with the clinician. All patients and parents were given written and verbal information in either French or English and gave verbal consent. Using a non-imaging 2Hz probe, the patients were screened by a specialist registrar in haematology (ST) under the supervision of an experienced consultant paediatric neurologist (FJK). All data was recorded manually and then transcribed onto the Trust’s blood results system. Results. TCD screening took an average of 15 minutes for a healthy patient and 30 minutes for a patient with known neurological problems. A further one hour per 10 patients was required to load the data onto the computer system. Of 67 patients screened (100% of those given appointments; 63 SCA), 5 of whom had already had a stroke, 7 (10%; 1 stroke) had abnormal TCD, 10 (14%, 1 stroke) were conditional and 2 (3%; 1 stroke) had low velocities. The 4 patients with haemoglobin SC disease had normal TCD. There was no effect of gestational age, birth weight or mode of delivery. Summary and Conclusions. The prevalences of abnormal and conditional TCD appear similar to previously reported data. Compliance was excellent. Those with previous infarction take longer to screen. Time is required to upload the results to the hospital computer system but the clinicians in charge of the patients voiced great satisfaction with the easy retrieval of results. A follow-up questionnaire will be looking at patient’s satisfaction and the screening program for the rest of the cohort is planned

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Contributors

Author: F. J. Kirkham

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