American Society of Hematology

Case Study: Sickle Cell Disease – A 25-Year-Old in Transition

A 25-year-old woman with a history of sickle cell disease (SCD) presents to the clinic for follow-up after a hospitalization for a vaso-occlusive pain crisis complicated by influenza A. She has a history of an acute ischemic stroke at age 5 years and has received monthly, simple red cell transfusions since the stroke. Her last transfusion was approximately four months prior. She is taking deferasirox 20 mg/kg daily but occasionally misses doses.

Laboratory results show the following:

Hemoglobin7.5 g/dL
Hematocrit 24%
Leukocyte count9,300/mm3
Platelet count202,000/m3
Mean corpuscular volume105 fL
Hemoglobin electrophoresis92% HbS, 6% HbF, 2% HbA2
Aspartate aminotransferase24 U/L
Alanine aminotransferase45 U/L
Ferritin 1,300 ng/mL

Which of the following is the next best step in diagnosis

  1. Restart scheduled red blood cell transfusions
  2. Start prophylactic penicillin
  3. Discontinue transfusions and start hydroxyurea
  4. Order transcranial doppler ultrasonography (TCD) to assess risk of stroke
  5. Increase dose of deferasirox to 25 mg/kg/day

Answer

  1. Restart scheduled red blood cell transfusions

Explanation

The incidence of primary stroke in children with SCD is 0.6 to 0.8 events per 100 patient-years, with a cumulative incidence of 7.8 percent by age 14 years in the Jamaican cohort and 11 percent by age 20 years in the U.S. Cooperative Study of Sickle Cell Disease. Once stroke has occurred, the incidence of recurrent (secondary) stroke ranges from 47 to 93 percent in patients not started on regular transfusions. The Stroke Prevention Trial in SCD (STOP) randomized 130 high-risk children with SCD to either transfusion therapy (to maintain HbS 30%) or observation. These high-risk children had an increased blood flow in the internal carotid or middle cerebral artery by TCD. This study showed a 92 percent reduction in incidence of first stroke in transfused high-risk patients. A follow-up study, STOP2, randomly assigned 72 children whose TCD had normalized after 30 months of transfusion therapy to either ongoing or discontinued transfusions. The study was closed early due to a significant increase in abnormal TCD velocity and stroke risk for those who halted transfusion therapy.

The multicenter phase III TWiTCH trial evaluated children with SCA and abnormal TCD velocities without a history of stroke on chronic transfusions. Data showed that hydroxyurea at maximal tolerated dose was noninferior to chronic transfusions for maintaining TCD velocities as primary stroke prophylaxis (choice C). This patient has a history of ischemic stroke, so the results of TWiTCH do not apply to her.

The Stroke with Transfusions Changing to Hydroxyurea (SWiTCH) study was designed as a phase III multicenter trial to determine the efficacy of hydroxyurea/phlebotomy, compared with transfusions/chelation for children with SCA, stroke, and iron overload in secondary stroke prophylaxis. The primary endpoint was a composite of noninferiority for stroke prevention and superiority for reduction of liver iron content. The trial was terminated at the first scheduled interim analysis for futility for the composite endpoint, which required superiority of phlebotomy over iron chelation for reducing excess iron stores. The incidence of stroke on the hydroxyurea plus phlebotomy arm was higher (7 of 67 patients; 10.4%) than in the transfusion plus chelation arm (1 of 66 patients; 1.5%). These results, though not powered for inferiority, showed a trend towars increased stroke risk with transition to hydroxyurea. In patients with prior stroke, cessation of transfusion therapy is currently not recommended.

Whether chronic transfusion therapy can be stopped after a longer period of transfusions in a patient with a prior stroke remains unclear even though risk of recurrent stroke remains high in adolescence and young adulthood. In patients older than 16 years, TCD velocity criteria to determine stroke risk is not reliable (choice D).

In the Prophylaxis with Oral Penicillin in Children with Sickle Cell Anemia trial, children with SCA were randomly assigned to receive oral prophylactic penicillin or placebo PROPS 1986). The trial ended eight months early after the occurrence of 15 cases of pneumococcal sepsis, 13 in the placebo group and two in the penicillin group, showing an 84 percent reduction in pneumococcal sepsis with penicillin prophylaxis. The follow-up study, PROPS II, did not show an increased risk in pneumococcal infections with discontinuation of prophylactic penicillin after age 5 years. Therefore, prophylactic penicillin is not recommended in adults with SCA (choice B).

The trajectory of ferritin in this patient has not been established and an increase in oral iron chelation is not indicated at this time.

Case Study submitted by Marquita Nelson, MD, of University of Chicago, Chicago, IL.

References

  1. Hirst C, Owusu-Ofori S Prophylactic antibiotics for preventing pneumococcal infection in children with sickle cell disease. Cochrane Database Syst Rev. 2014 6:CD003427.
  2. Valadi N, Silva GS, Bowman LS, et al Transcranial Doppler ultrasonography in adults with sickle cell disease. Neurology. 2006 22:572-574.
  3. Ware RE, Davis BR, Schultz WH, et al Stroke with transfusions changing to hydroxyurea (SWiTCH). Blood. 2012 119:3925-3932.
  4. Kumar N, Gross JB Jr, Ahlskog JE TCD with transfusions changing to hydroxyurea (TWiTCH): hydroxyurea therapy as an alternative to transfusions for primary stroke prevention in children with sickle cell anemia. Blood. 2015 126:3.
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