Sickle cell disease: diagnosis and health maintenance: Case

This boy has HbSS sickle cell disease, well managed on penicillin, hydroxyurea, and full immunisation, and the new finding is the abnormal transcranial Doppler. The right middle cerebral artery time-averaged mean velocity of 205 cm per second crosses the 200 cm per second threshold that defines the abnormal result, and this is a pre-stroke state that demands action. The annual trend, up from 175 cm per second last year, confirms that this is a new and real change rather than a measurement artefact. ^[3]

Interpretation of the findings

The key findings are the abnormal transcranial Doppler, the steady-state chronic haemolysis, and the good hydroxyurea response. The time-averaged mean velocity of 205 cm per second is abnormal, because the threshold is 200 cm per second or more, and the STOP trial showed that such a child has a high risk of a first stroke without treatment. The haemoglobin of 78 g per litre and the reticulocyte count of 12 percent are the expected steady state of HbSS, the chronic haemolysis, and the fetal haemoglobin of 18 percent shows a good response to the hydroxyurea, which is why his disease has been well controlled to this point. ^[8]

The penicillin and the immunisation are appropriately maintained, and there is no sign yet of organ injury. The question is not whether he is sick today, because he is not, but whether the abnormal Doppler is allowed to progress to a stroke, which it will in a substantial minority of untreated children. The interpretation is therefore that the boy has moved from a screened, low-risk child to one who needs a chronic transfusion programme to prevent a stroke. ^[3]