Patients with sickle cell disease are frequently excluded from the benefits of transcranial doppler screening for the risk of stroke despite extensive and compelling evidence

Transcranial doppler as screening method for sickling crises in children with sickle cell anemia: a latin America cohort study

Background

Sickle cell anemia (SCA) is the leading cause of childhood stroke. We aimed to evaluate whether altered cerebral flow velocities, as measured by transcranial Doppler (TCD), are associated with vaso-occlusive complications in addition to stroke in pediatric SCA patients.

Methods

We evaluated 37 children aged between 2 and 16 years with SCA who underwent screening for TCD between January 2012 and October 2018. Genotypic profiles and demographic data were collected, TCD examinations were performed during follow-up, and the presence of sickling crises was compared. Survival analyses were performed using simple frailty models, in which each predictor variable was analyzed separately in relation to the occurrence of a sickling crisis.

Results

The variables related to sickle cell crises in the univariate analysis were peak systolic velocity (PSV) in the middle cerebral artery (MCA), hazard ratio (HR) 1.01 (1.00—1.02) p = 0.04; end-diastolic velocity (EDV) in the MCA, HR 1.02 (1.01—1.04) p = 0.01; time average mean maximum velocity (TAMMV) in the basilar artery (BA), HR 1.02 (1.00—1.04) p = 0.04; hemoglobin, HR 0.49 (0.38—0.65) p < 0.001; hematocrit, HR 0.78 (0.71—0.85) p < 0.001; leukocyte counts, HR 1.1 (1.05—1.15) p < 0.001; platelets counts, HR 0.997 (0.994—0.999) p = 0.02; and reticulocyte numbers, HR 1.14 (1.06—1.23) p < 0.001.

Conclusions

Our results indicate PSV and EDV in the MCA and TAMMV in the BA as markers of risk for the occurrence of sickling crises in SCA.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12887-022-03429-5.

Transcranial Doppler Velocities among Sickle Cell Disease Patients in Steady State

Transcranial Doppler (TCD) screening is an established tool to identify children with sickle cell disease at high risk of stroke. Our objective was to study TCD velocities among sickle cell disease patients while in a steady state. This cross-sectional study included 78 steady state sickle cell disease patients [31 Hb SS (β^S/β^S) (sickle cell anemia), 47 Hb S/β-thalassemia (HBB: c.20A>T/β-thal)], attending the Pediatric Hematology Clinic at Cairo University Children's Hospital, Cairo, Egypt. All patients underwent TCD velocity assessment as per the Stroke Prevention Trial in Sickle Cell Anemia (STOP) protocol. In our cohort, TCD velocities were comparable among Hb S/β-thal vs. SS patients. Hemolysis indicators correlated significantly to TCD velocities in Hb S/β-thal patients; positive correlation was found between total bilirubin level and right middle cerebral artery (MCA) and right distal internal carotid artery (dICA) TCD velocities (r = 0.428, p = 0.00, r = 0.360, p = 0.01), respectively as well as between reticulocyte count and right MCA, right dICA and right anterior cerebral artery (ACA) TCD velocities (r = 0.424, p = 0.01), (r = 0.40, p = 0.00), (r = 0.303, p = 0.04), respectively. On the other hand, statistically significant negative correlations were found between hemoglobin (Hb) level and right ACA, right dICA TCD velocities (r = -0.290, p = 0.05), (r = -0.324, p = 0.03). Although Hb F is considered an ameliorating factor for disease severity; hemolysis stands as an indicator of risk for TCD velocity elevation, and in turn, risk for stroke among sickle cell disease patients.

Asymmetric Dimethylarginine Levels and Its Correlation to Cerebral Blood Flow in Children with Sickle Cell Anemia

Asymmetric dimethylarginine (ADMA) level may play a role in the pathogenesis of cerebrovascular stroke in Children with Sickle Cell Anemia (SCA). To assess the plasma level of ADMA in children with SCA and its correlation to cerebral blood flow. This is a cross sectional study was carried out on 30 children with homozygous SCA under follow up in the Out Patients Clinic, Pediatric Department at Tanta University Hospital and 30 healthy children as a control group. Both groups had undergone the following investigations: Complete blood count, lactate dehydrogenase enzyme, and plasma level of ADMA by a commercial ADMA ELISA Kit. Trans-cranial Doppler were done for both groups. ADMA plasma level was significantly higher in-patient group in comparison to the control group (p < 0.001), with a mean value 1.43 ± 0.20 μmol/l, 0.48 ± 0.16 μmol/l respectively. The time-averaged mean maximum velocities for middle cerebral artery, anterior cerebral artery, inferior cerebral artery and posterior cerebral artery were significantly different between patient and control group, p < 0.05. Trans-cranial Doppler data revealed that, 86.7% of patients have low velocity (< 70 cm/s) and 13.3% having very low velocity (< 10 cm/s) while control group have normal velocity. There was a significant negative correlation between ADMA plasma levels and cerebral blood flow. Elevated ADMA levels may have a role in the pathogenesis of the decreased cerebral blood flow in children with SCA.

Changes in Transcranial Doppler Flow Velocities in Children with Sickle Cell Disease: The Impact of Hydroxyurea Therapy

BACKGROUND AND OBJECTIVES

Hydroxyurea (HU) was recently described as a substitute for chronic transfusion for children with sickle cell disease (SCD) and abnormal transcranial Doppler (TCD) velocities who have received at least 1 year of transfusions. However, the role of HU in reverting elevated TCD velocities in patients not treated with transfusion is still debatable. The objective of the study was to examine whether HU influences the progression of TCD velocities in children with SCD.

PATIENTS AND METHODS

Children with SCD with at least 2 TCDs not less than 6 months apart were evaluated over 51 months. Time-averaged maximum mean (TAMM) velocities for the initial and the last transcranial Doppler examinations were noted and differences compared between HU and HU-naive groups.

RESULTS

Overall, 68.8% of the HU-group with elevated TCD velocities compared with 40.0% of the HU-naive experienced TCD reversal (P = .047). A higher proportion of the HU-naive group, 7 (14.3%) versus 9.8% of the HU group experienced TCD conversion. Those with initial conditional velocities in the HU-group experienced a significant reduction in TAMM velocities (from 176.8 ± 5.3 to 162.7 ± 13.9 cm/s, difference of 14.1 cm/s; P = .001) unlike those in the HU-naive group (176.3 ± 5.3 to 170.0 ± 18.6 cm/s, difference of 6.3 cm/s; P = .148). The change in the TAMM velocities was also significantly higher among the HU-group (14.1 ± 12.4 cm/s versus 6.3 ± 18.5 cm/s, P = .015).

CONCLUSION

Our data suggest a beneficial role of HU in TCD velocity reduction in patients not treated with chronic transfusions, particularly among those with initial conditional TCD velocities.