Corrected QT Interval Is Related to Markers of Hemolysis and Tricuspid Regurgitant Jet Velocity in a Young Cohort with Sickle Cell Disease.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 2258-2258
Author(s):  
Robert I. Liem ◽  
Luciana T. Young ◽  
Alexis A. Thompson

Abstract Recent evidence suggests that prolongation in QT interval may be a frequent finding in patients with sickle cell disease (SCD). Few studies, however, have examined the relationship between conduction abnormalities and other cardiac complications, such as left ventricular hypertrophy (LVH) and tricuspid regurgitant jet velocity (TRJV) elevation, in this population. Moreover, long QT may be a marker of increased mortality in conditions, other than SCD, associated with LVH. We therefore sought to evaluate QT interval and its relationship to echocardiographic findings, laboratory parameters and disease severity in a cohort of children and young adults with SCD. Methods We prospectively evaluated the corrected QT interval (QTc) on standard 12-lead ECG in a cross-sectional, convenience sample of 73 subjects (41 males, mean age 14.2±3 years, range 10 to 24) with Hb SS, SC and S-β0 thalassemia undergoing screening for TRJV elevation. Subjects on chronic transfusions were excluded and all studies were performed at baseline on the same day. A review of available medical records was also performed. Results In our cohort, QTc (mean 436±24 ms, range 387 to 531) was prolonged > 440 ms in 30/73 (41%) of subjects at steady state. We also found TRJV elevation ≥ 2.5 m/s in 24/73 (33%) and LVH by ECG or echocardiographic criteria in 32/73 (44%) subjects. Using Pearson’s correlation coefficient, we observed significant correlations between QTc and TRJV (r=0.38, p=0.002), WBC (r=0.37, p=0.001) and several markers of hemolysis, including LDH (r=0.46, p=0001), Hb (r=-0.32, p=0.005), retic (r=0.29, p=0.013), plasma Hb (r=0.27, p=0.03) and AST (r=0.38, p=0.001). Using Student’s t-test for independent samples, only TRJV (2.55±0.33 vs. 2.34±0.26 m/s, p=0.006), LDH (450±166 vs. 329±143 U/L, p=0.001), WBC (10.6±4.7 vs. 8.6±3.3×109/L, p=0.048), retic (14.4±9.2 vs. 10.6±6.1%, p=0.039) and AST (50±22 vs. 38±15 U/L, p=0.009) were significantly higher and Hb (9.1±1.3 vs. 9.9±1.7 g/dL, p=0.04) lower in subjects with QTc > 440 ms compared to those with QTc ≤ 440 ms. We found no significant relationship between QTc and age, LV mass, platelet count or fetal Hb. By χ2 analysis, a larger proportion of subjects with QTc > 440 ms also had a history of acute chest syndrome (p=0.007), gallstones (p=0.047), exchange transfusion (p=0.04) and to a less significant degree, TRJV elevation (p=0.112). Prolonged QTc was not affected by sex, hydroxyurea use or a history of LVH, frequent pain, asthma, splenectomy, priapism and tonsilloadenoidectomy. Given sample size limitations and data reduction methods, we found by logistic regression analysis that the combination of TRJV and history of acute chest syndrome best predicted QTc prolongation, correctly identifying 80% of cases and resulting in positive and negative predictive values of 76% and 81%, respectively. Conclusions We conclude that QTc prolongation is common in a prospectively screened cohort of young sickle cell patients at baseline and is associated with evidence of hemolysis and to a lesser degree, TRJV elevation. Our results contrast with findings in other conditions that link QTc prolongation primarily to LVH. Future studies will be critical to further define QTc variability, pathophysiologic determinants as well as the clinical consequences of conduction abnormalities, which may or may not relate to TRJV elevation, in the sickle cell population.

2021 ◽  
pp. 1-5
Author(s):  
Justin E. Juskewitch ◽  
Craig D. Tauscher ◽  
Sheila K. Moldenhauer ◽  
Jennifer E. Schieber ◽  
Eapen K. Jacob ◽  
...  

Introduction: Patients with sickle cell disease (SCD) have repeated episodes of red blood cell (RBC) sickling and microvascular occlusion that manifest as pain crises, acute chest syndrome, and chronic hemolysis. These clinical sequelae usually increase during pregnancy. Given the racial distribution of SCD, patients with SCD are also more likely to have rarer RBC antigen genotypes than RBC donor populations. We present the management and clinical outcome of a 21-year-old pregnant woman with SCD and an RHD*39 (RhD[S103P], G-negative) variant. Case Presentation: Ms. S is B positive with a reported history of anti-D, anti-C, and anti-E alloantibodies (anti-G testing unknown). Genetic testing revealed both an RHD*39 and homozygous partial RHCE*ceVS.02 genotype. Absorption/elution testing confirmed the presence of anti-G, anti-C, and anti-E alloantibodies but could not definitively determine the presence/absence of an anti-D alloantibody. Ms. S desired to undergo elective pregnancy termination and the need for postprocedural RhD immunoglobulin (RhIG) was posed. Given that only the G antigen site is changed in an RHD*39 genotype and the potential risk of RhIG triggering a hyperhemolytic episode in an SCD patient, RhIG was not administered. There were no procedural complications. Follow-up testing at 10 weeks showed no increase in RBC alloantibody strength. Discussion/Conclusion: Ms. S represents a rare RHD*39 and partial RHCE*ceVS.02 genotype which did not further alloimmunize in the absence of RhIG administration. Her case also highlights the importance of routine anti-G alloantibody testing in women of childbearing age with apparent anti-D and anti-C alloantibodies.


Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 3759-3759
Author(s):  
Onyinye C. Onyekwere ◽  
Andrew Campbell ◽  
James Williams ◽  
Peter Gaskin ◽  
Sohail Rana ◽  
...  

Abstract Despite the high prevalence of PHTN in adults with SCD, the prevalence in the pediatric population with SCD is not known. We hypothesized that elevated pulmonary artery pressures may be found in SCD adolescents with history of pulmonary complications, such as acute chest syndrome (ACS), obstructive sleep apnea (OSA), asthma, and reactive airway disease. Thirty such sickle cell disease adolescents were screened at Howard University or University of Michigan for PHTN with Doppler echocardiography. We defined PHTN as a tricuspid regurgitant jet velocity (TRV) of at least 2.5 m/sec (corresponding to a pulmonary artery systolic pressure greater than 35 mm Hg). PHTN was found in 16 SCD patients (53.3%) and 5 (16.7%) had TRV > 3.0 m/sec. Clinical findings according to the presences or absence of PHTN are shown in the table. Potential factors contributing to PHTN in patients with SCD include chronic hemolysis and chronic hypoxia. Our results suggest that PHTN is common among SCD adolescents with a history of pulmonary complications. Consideration should be given to screening such patients for PHTN and exploring treatment options. Further studies are urgently needed to clarify the prevalence and mechanisms of PHTN in adolescents with SCD. Clinical and demographic data of 30 SCD adolescents with pulmonary findings who underwent echocardiography at Howard University Hospital or University of Michigan PHTN (N = 16) No PHTN (N = 14) P Age in years (mean +/− SD) 15.9 +/− 3.2 17.4 +/− 2.3 0.17 Females (no. and %) 5 (31.3) 7 (50) 0.5 Hemoglobin SS Phenotype (no and %) 14 (87.5 11 (78.6) 0.5 Hemoglobin concentration (mean +/− SD) 8.0 +/− 2.1 9.3 +/−1.9 0.11 White blood cells (mean +/− SD) 10.9 +/− 2.9 9.7 +/− 3.7 0.4 Platelet (mean +/− SD) 475 +/− 172 364 +/− 240 0.17 Hemoglobin F percent (mean +/− SD) 5.1 +/− 3.5 6.4 +/− 5.5 0.6 Lactate dehydrogenase (mean +/− SD) 505 +/− 162 264 +/− 50 0.002 Total bilirubin (mean +/− SD) 4.1 +/− 2.6 3.4 +/− 2.6 0.5 Creatinine concentration (mean +/− SD) 0.6 +/− 0.2 0.7 +/− 0.2 0.18 Aspartate transaminase (mean +/− SD) 48 +/− 27 36 +/− 16 0.18 Alanine transaminase (mean +/− SD) 51 +/− 37 39 +/− 20 0.3


Blood ◽  
2001 ◽  
Vol 97 (11) ◽  
pp. 3628-3632 ◽  
Author(s):  
Alina Ferster ◽  
Parvine Tahriri ◽  
Christiane Vermylen ◽  
Geneviève Sturbois ◽  
Francis Corazza ◽  
...  

The short-term beneficial effect of hydroxyurea (HU) in sickle cell disease (SCD) has been proven by randomized studies in children and adults. The Belgian registry of HU-treated SCD patients was created to evaluate its long-term efficacy and toxicity. The median follow-up of the 93 patients registered is 3.5 years; clinical and laboratory data have been obtained for 82 patients at 1 year, 61 at 2 years, 44 at 3 years, 33 at 4 years, and 22 after 5 years. On HU, the number of hospitalizations and days hospitalized dropped significantly. Analysis of the 22 patients with a minimum of 5 years of follow-up confirm a significant difference in the number of hospitalizations (P = .0002) and days in the hospital (P < .01), throughout the treatment when compared to prior to HU therapy. The probabilities of not experiencing any event or any vaso-occlusive crisis requiring hospitalization during the 5 years of treatment were, respectively, 47% and 55%. On HU, the rate per 100 patient-years of severe events was estimated to be 3.5% for acute chest syndrome, 1.2% for aplastic crisis, 0.4% for splenic sequestration; it was 0% for the 9 patients with a history of stroke or transient ischemic attack followed for an average of 4 years. No important adverse effect occurred. Long-term chronic treatment with HU for patients with SCD appears feasible, effective, and devoid of any major toxicity; in patients with a history of stroke, HU may be a valid alternative to chronic transfusion support.


Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 4909-4909
Author(s):  
Timothy Klouda ◽  
Nataly Apollonsky ◽  
Deepti Raybagkar ◽  
Bruce Bernstein

Abstract Title: Hematological Changes from Baseline in Children with Sickle Cell Disease Admitted for Acute Chest Syndrome Compared to Acute Pain Crisis Authors: Timothy Klouda1, Deepti. Raybagkar2, Bruce Bernstein1, Nataly Apollonsky2, Institutes:1Pediatrics, St Christopher's Hospital for Children, Philadelphia, PA, United States, 2Hematology, St Christopher's Hospital for Children, Philadelphia, PA, United States, Introduction: Children with Sickle Cell Disease suffer from multiple complications including acute pain crisis (VOC) and acute chest syndrome (ACS). Nearly 30% of children with SCD have had one episode of ACS, with the incidence higher in early childhood. The proposed pathophysiology of ACS is thought to be multi-factorial, with pulmonary fat embolism or infectious etiology being identified in a large number of patients. Increased sickling due to hypoxemia or pain has been shown to place patients at risk for ACS development., Studies have shown an increase in inflammatory markers including leukocytes and neutrophils, along with a decreased hemoglobin in SCD children who developed ACS, but no studies to date have compared laboratory changes during the acute illness to their baseline values. We hypothesized that children with SCD who are admitted for ACS will have a larger decrease in hemoglobin from baseline and a higher increase in white blood cell count from baseline when compared to those admitted for an acute pain crisis. Methods: Through retrospective chart review of patients with SCD admitted to St.Christopher's Hospital for Children we identified 45 patients with ACS. Laboratory data collected on admission from chart review included SCD genotype, age, BMI, hemoglobin, white blood cell count, absolute neutrophil count, absolute eosinophil count, platelets, reticulocyte count, hemoglobin F, vital signs and medication history. All 45 children had laboratory data collected from an acute pain crisis that occurred during a different admission for comparison. Collected data was compared to baseline laboratory data, collected during routine visit at sickle cell clinic within 1 year of admission. Changes in laboratory data from baseline during admission for ACS were compared to changes during admission for uncomplicated VOC. Results: Children with SCD who were admitted or developed ACS during admission had a larger increase in leukocyte count (6.99 vs 4.18, p=0.027) and neutrophil count (6.3 vs 3.74, p=0.04) from baseline compared to those admitted for VOC alone. Patients with ACS development also had a larger decrease in platelets (-124.74 vs -56.21, p=.047) from baseline when compared to VOC admissions. There was no statistically significant change from baseline labs when comparing hemoglobin (p=0.10), eosinophil count (p=.382), reticulocyte count (p=0.754), AST (p=0.061) and ALT (p=0.082) in the ACS and VOC groups. Children with a history of 2 or more lifetime ACS were more likely to have OSA (p=0.021), 3 or more VOCs in the past year (p=0.002), and a history of splenectomy, but it was not found to be statistically significant (p=0.155) Conclusion: Children with SCD who developed or were admitted with ACS had a significant increase in leukocyte and neutrophil count from baseline, and a decrease in platelets when compared to VOC admissions. There was no significant change from baseline in hemoglobin, reticulocyte and eosinophils detected. Future larger and multi-center prospective studies need to be performed to confirm the various changes identified in hematological markers seen in ACS vs VOC. Disclosures No relevant conflicts of interest to declare.


Author(s):  
Akaba Kingsley ◽  
Edu C. Betta ◽  
Akaba Edakabasi ◽  
Essien Ofonime ◽  
Bibia Glory Philemon

Background: Sickle cell disease (SCD) patients have greater susceptibility to infections, they are reckoned to be vulnerable patients during the current COVID-19 pandemic. SCD patients are commonly affected by pulmonary complications such as acute chest syndrome (ACS), pulmonary embolism (PE) and pneumonia that contribute significantly to mortality risks. Aim: The study was aimed at showing the impact of SARS-COV viral pandemic on SCD patients. Presentation of Case: A 42-year-old male known sickle cell disease patient, who presented with a 5 days’ history of chest pain and difficulty in breathing with a pain score of 8/10. Pain was said to be localized and, subside on the ingestion of analgesics (Tab DF118/60mg and PCM 1000mg) with no known aggravating factor, but there was associated history of difficulty in breathing. The patient was being managed as a case of vaso-occlusive crises R/O acute chest syndrome, and was commenced on adequate hydration, oxygen saturation was between 95-85%. On examination, respiratory rate was 20 cycles per minute, pulse rate – 96 beats/minute, BP and chest examination were essentially normal. CBC showed the Packed Cell Volume of 31%, White Blood Cells 15.04 x 109/L, Neutrophils 7.51x103/µL Lymphocyte 6.50 x103/µL, Monocyte 0.76 x103/µL Eosinophils 0.20x103/µL, Basophils 0.05x103/µL, Platelet 358. The electrolytes (Na-135 mmol/L, K 3.5mmol/L, HCO3-20), urea -10 mmol/L and creatinine (88mmol/L) were normal, the chest x-ray showed cardiomegaly but the lung fields were clear. The patient was administered ceftriaxone (prophylactic antibiotics – 1 g daily).  The patient tested positive to COVID-19 and was immediately transferred to the isolation centre for proper management. He was commenced on oral medication, azithromycin, dexamethasone, ivermectine, amoxicillin/clavulanic acid, vitamin C, clexane and the analgesic was changed to paracetamol and dihydrocodeine to alternate 3 hourly with accordance to the national guidelines. In addition, he was administered subcutaneous enoxaparin due to the hypercoagulability state of SCD. The patient’s health status improved within 24hours of commencement of the above medications and remained stable all through the period of isolation and a repeat covid-19 test was done 15 days of admission using and reverse transcriptase PCR and was discharged home according to the National protocol. Conclusion: Studies and clinical trials are essential to evaluate effective diagnostic and management options for SCD patients and other high-risk conditions like diabetes hypertension, cancer patients and so on that are associated with fatal complications when infected with COVID-19 and similar diseases.


2019 ◽  
Vol 2019 ◽  
pp. 1-3 ◽  
Author(s):  
Christoph Sossou ◽  
Ogechukwu Chika-Nwosuh ◽  
Christopher Nnaoma ◽  
Jose Bustillo ◽  
Asad Chohan ◽  
...  

Acute chest syndrome (ACS) is a feared complication of sickle cell disease. Here is a case of a patient who presented with symptoms suggestive of acute chest syndrome yet had a delayed diagnosis presumably due to the lack of documented history of sickle cell disease of the patient, consequently evolving into acute respiratory distress syndrome (ARDS). He was subsequently diagnosed with heterozygous sickle cell SC disease on hemoglobin electrophoresis. After appropriate management with mechanical ventilator, broad-spectrum empiric intravenous antibiotics, exchange transfusion, and intravenous fluid resuscitation, the patient was medically optimized and safely discharged home, with significant improvement noted on successive follow-up visits.


Chest Imaging ◽  
2019 ◽  
pp. 141-145
Author(s):  
Constantine Raptis

“Sickle cell disease” describes the spectrum of pathology in patients with at least one HbS chain and one other abnormal β‎ globin chain. Although patients with sickle cell disease often present with a simple community acquired pneumonia, acute chest syndrome must be considered in patients presenting with chest pain and fever, as it carries an increased risk of mortality, especially in adults. A few other entities, including rib infarction and subdiaphragmatic pathologies, can mimic the symptoms of acute chest syndrome. Finally, the findings of sickle cell disease on chest radiography will be discussed. Radiologists must be familiar with these findings in order to accurately interpret imaging studies, especially when the history of sickle cell is not provided.


Blood ◽  
1993 ◽  
Vol 81 (12) ◽  
pp. 3422-3427 ◽  
Author(s):  
WR Rackoff ◽  
N Kunkel ◽  
JH Silber ◽  
T Asakura ◽  
K Ohene-Frempong

The observation of low transcutaneous arterial oxygen saturation (SaO2) in otherwise well sickle cell patients has lead to questions about the interpretation of pulse oximetry values in these patients. We undertook a prospective study of children with sickle cell disease to (1) determine the prevalence of, and factors associated with, low transcutaneous SaO2 in clinically well patients, (2) develop an algorithm for the use of pulse oximetry in acutely ill patients, and (3) assess the accuracy of pulse oximetry in these patients. Eighty-six clinically well children with hemoglobin (Hb) SS had a lower mean transcutaneous SaO2 than 22 Hb SC patients and 10 control subjects (95.6% v 99.1% v 99.0%, respectively; p < .001). In Hb SS patients, a history of acute chest syndrome and age greater than 5 years were associated with lower transcutaneous SaO2 (mean 93.8% for those with a history of acute chest syndrome v 97.8% for those without a history of acute chest syndrome, and 94.0% for patients = 5 years old v 97.2% for those < or = 5 years old; P < .001). These associations were not seen in Hb SC patients. During acute illness, Hb SS patients with acute chest syndrome had transcutaneous SaO2 values that were less than 96% and at least 3 points lower than measurements made when they were well. A nomogram was designed to aid in the interpretation of transcutaneous SaO2 in acutely ill Hb SS patients when a comparison value is not available. The accuracy of pulse oximetry was shown by the correlation between SaO2 measured by pulse oximetry and calculated by using the patient's oxygen dissociation curve and PaO2 (r = .97). This study provides evidence that Hb oxygen desaturation is not a universal finding among children with sickle cell disease and identifies factors associated with Hb oxygen desaturation. We conclude that pulse oximetry may be useful to assess whether progressive pulmonary dysfunction begins at an early age in Hb SS patients, and to assess acutely ill patients for the presence of hypoxemia associated with acute chest syndrome.


Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 3117-3117
Author(s):  
Sherraine Della-Moretta ◽  
William Marshall ◽  
Rui Li ◽  
Erin Cleary ◽  
Philip Samuels ◽  
...  

Abstract Background Approximately 100,000 Americans are affected by sickle cell disease (SCD), an inherited hematologic disorder. In women with sickle cell disease, pregnancy is associated with increased maternal and fetal adverse outcomes (Elenga et al). However, there is a paucity of data on risk factors for adverse events in this population. This retrospective study seeks to add to the deficient repertoire of information regarding maternal and fetal outcomes in patients with sickle cell disease and their children. Methods We retrospectively evaluated pregnancy outcomes of women with SCD who had previously undergone echocardiography from the year 2000-2021. The associations between clinical variables and adverse hematologic (AHE), cardiac (ACE), obstetric (AOE) and fetal/neonatal (ANE) events were evaluated by the Generalized Linear Model (GLM). The adverse hematologic events were vaso-occlusive crisis (VOC) antepartum and postpartum, acute chest syndrome, venous thromboembolism antepartum and postpartum, and transfusion antepartum. Results We identified 43 women/59 pregnancies with a median maternal age 27 years old (interquartile range [IQR] 20), pre-pregnancy BMI 25 kg/m2 (IQR 16). Maternal sickle cell genotype was SS in 31 (72%) women/37 (63%) pregnancies, SC in 8 (18%) women/18 (31%) pregnancies, and other genotype in 4 (9%) women/4 (7%) pregnancies. Prior venous thromboembolism was present in 12 (27%) women/15 (25%) pregnancies and prior acute chest syndrome (ACS) in 33 (80%) women/41 (75%) pregnancies. In the year before pregnancy, 24 (56%) women were admitted at least once for VOC. There were no maternal deaths during pregnancy or up to 1 year postpartum. AHE (n = 171) occurred in 43 (73%) pregnancies (Figure A), with a median of 2 (range 0-13) AHE per pregnancy. AHE were more common with genotype SS, history of ACS, history of ³ 10 lifetime transfusions, admission for VOC in the year before pregnancy, tricuspid regurgitation velocity (TRV) &gt;2.5 m/s on echocardiogram, and increased maternal age, and less common with increased hemoglobin (Figure B). ACE were rare (n = 3) (Figure A) and weakly associated with increased maternal age (Figure C). AOE (n = 37) occurred in 27 (45%) pregnancies (Figure A) and were associated with lower pre-pregnancy maternal BMI (Figure D). ANE (n = 54) occurred in 27 (46%) of pregnancies, and were associated with maternal hypertensive disorders of pregnancy (Figure E). Conclusions We found that AHE during pregnancy in women with SCD were associated with genotype SS, history of ACS, ³ 10 lifetime transfusions, admission for VOC in the year before pregnancy, higher maternal age, and inversely related to hemoglobin. In addition, AHE during pregnancy were associated with TRV &gt;2.5 m/s on echocardiogram, which has not been previously shown in women with SCD. These data may be useful to identify women at increased risk during pregnancy. Data show that patients with sickle cell disease who have more disease-related complications including history of acute chest syndrome, frequent pain crisis, elevated TRV on echocardiogram, and lower hemoglobin are at greater risk for AHE. This suggests that disease severity is directly related to outcomes. The association between increased maternal age and ACE has been demonstrated in the past in women without SCD (DeViti et al). The same can be noted for the association of AOE with lower maternal BMI (Verma et al), and ANE being associated with maternal hypertensive disorders of pregnancy (Lugobe et al). In the future, prevention of these complications will be key. Future directions include determining the effect of disease-modifying therapy on these outcomes, though safety during pregnancy has not yet been demonstrated for more novel agents such as voxelotor and crizanlizumab. With more information on these risk factors, we hope that modification and treatment can result in better outcomes. Figure 1 Figure 1. Disclosures Desai: Pfizer: Other: Publication Fee, Research Funding; Foundation for Sickle Cell Research: Honoraria; Forma: Consultancy; Novartis: Research Funding, Speakers Bureau; Global Blood Therapeutics: Honoraria, Research Funding.


Blood ◽  
1994 ◽  
Vol 83 (4) ◽  
pp. 1124-1128
Author(s):  
EP Vichinsky ◽  
BH Lubin

Hydroxyurea can increase fetal hemoglobin (HbF) and improve the clinical course of sickle cell disease (SCD) patients. However, several issues of hydroxyurea therapy remain unresolved, including differences in patients' drug clearance, predictability of drug response, reversibility of sickle cell disease-related organ damage by hydroxyurea, and the efficacy of elevated HbF. We treated two patients with hydroxyurea for periods of 1 to 4 years, monitoring clinical course and laboratory parameters at regular intervals. The first patient (patient A) had a history of chronic pain and extensive hospitalizations. The second patient (patient B) had a history of stroke and refused to continue with chronic transfusion therapy and chelation. Both patients showed a fivefold to tenfold increase in HbF (5% to 25%, 3% to 31%). However, patient A developed an acute chest syndrome, despite an HbF level of 20%. After red blood cell transfusions for hypoxia, the HbF level decreased to 5%. When hydroxyurea dosage was increased, pancytopenia developed and was not resolved until 2 months after hydroxyurea was discontinued; Patient B developed a cerebral hemorrhage on hydroxyurea; he died shortly thereafter. His HbF level was 21% before death. We noted an increase in HbF and a general improvement in the two patients. However, both experienced major SCD-related complications despite HbF levels over 20%. Our findings also suggest that the progressive vascular changes associated with SCD are unlikely to be dramatically affected by increased HbF levels. Because neither the efficacy nor the toxicity of hydroxyurea have been thoroughly investigated, physicians should be cautious in prescribing hydroxyurea for patients with SCD before completion of the National Clinical Trial.


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