Sickle cell disease (SCD) affects haemoglobin - the molecule in blood cells which carries oxygen. It causes red blood cells to become abnormal crescent (or sickle)- shaped. Sickled red blood cells cannot travel through small blood vessels as easily as normal red blood cells which can lead to blockages. This means that oxygen may be prevented from getting to where it is needed. Individuals with sickle cell disease also suffer form abnormality in the lining of their blood vessels, which contributes to the damage.

Damage and blockage can occur in the blood vessels in the brain and means that children with sickle cell disease have a significant risk of suffering from strokes. Research has shown that transcranial Doppler ultrasonography can be used in this setting to identify children at most risk of getting strokes.

Ultrasound is therefore used in children with sickle cell disease to measure the blood flow in the vessels in the brain. This research has formed the basis of the National Health Service (NHS) Standard of Care for Sickle Cell Disease in the United Kingdom (UK) which uses transcranial Doppler ultrasonography at once a year to screen children with sickle cell disease aged 2 to 16.

Ultrasound is used because it is portable, does not uses ionising radiation such as x-rays, is non-invasive and gives good results. However, the results are dependent on the operator. This means that the screening service is provided by centres of excellence with experienced scanning staff visiting clinics in smaller hospitals with portable machines. There is a lack of research comparing the use of portable machines to laboratory-based machines. This is important because screening can identify children at high risk of stroke and may be used by clinical staff to make a decision about the care of the child.

Please see above

Inclusion Criteria:

• Clinical Diagnosis of Sickle Cell Disease
• Under surveillance as part of the NHS Sickle Cell & Thalassaemia Screening Programme
• Children between the ages of 2 - 16 years old. Those under 16 years of age must be accompanied by a responsible adult.

Exclusion Criteria:

• Participants older than 16 years of age as this is outside the scope of the sickle cell screening programme.
• Individuals unable to give fully informed and voluntary consent.
• Individuals with inadequate temporal windows as it will not be possible to record measurements of velocity.

4 months period