source: The American Society of Pediatric Hematology/Oncology

year: 2016

authors: Emily R. Meier, Paul Levett

Background: All patients with HbSS (SCA) share the same genetic mutation but the clinical phenotype is variable and difficult to predict early in life. The only available cure for SCA is hematopoeitic stem cell transplant (HSCT). Early trials of HSCT in SCA patients revealed that SCA patients have higher complication rates which increase with age than other patients undergoing HSCT. If a reliable severity predictor existed, HSCT could be performed in those patients with SCA who are at highest risk of SCA complications prior to the onset of vasculopathy and organ damage.

Objectives: The goal of this project was to systematically review the literature to determine which disease severity predictors have been validated in pediatric patients with SCA.

Design/Method: A search of PubMed, Cochrane Clinical Trials Register, and Scopus was performed using the following terms: sickle cell anemia or disease, complications, mortality, classification, prognosis, severity of illness, predictive value of test, risk, proportional hazards model, stroke risk, hematopoietic stem transplantation methods. Data were extracted using a standardized data collection form.

Results: The full text of 53 of the 590 (9.0%) references identified was reviewed based on the title/abstract. Thirty-three articles (62.3%) are included in this analysis; 20 articles were excluded based on pre-determined exclusion criteria. Fetal hemoglobin (HbF) and alpha globin gene number were the most commonly studied severity predictors (7 studies each) with hemoglobin (6), white blood cell count (5) and absolute reticulocyte count (4) rounding out the top 5 studied predictors in this systematic review. Nearly three quarters (5/7) of the HbF studies reported beneficial effects with increasing HbF levels; however, increased HbF levels were not associated with lower rates of hospitalization or stroke risk in two articles. Increasing ARC was positively associated with increasing risk of cerebro-vascular complications in all 3 of the reports in which it was studied, while alpha thalassemia trait was protective against stroke and abnormal TCD, but not rate of painful crisis.

Conclusion: The ability to predict SCA complications was mixed for all studied variables, including HbF. More reliable predictors of disease complications are urgently needed to guide therapeutic decisions in pediatric patients with SCA.

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