Background: Sickle cell disease (SCD) is the most common hemoglobinopathy, occurring worldwide, and vaso-occlusive events (VOEs) are its paramount, hallmark clinical manifestation. Evidence exists that platelets play an important role in generating VOEs.
Objective: To assess the clinical benefits and harms of antiplatelet agents for preventing VOEs in patients with SCD.
Methods: We conducted searches of the Cochrane Central Register of Controlled Trials (CENTRAL; up to 2018, issue 3 of 12), PubMed/MEDLINE (up to April 20, 2018), and the Excerpta Medica database (EMBASE; from 1980 to week 16 of 2018). We also searched the Latin American and Caribbean Health Sciences Literature (LILACS) database, the US Food and Drug Administration (FDA) website, the European Medicines Agency (EMA) website, the World Health Organization International Clinical Trials Registry Platform (WHO ICTRP), and www.ClinicalTrials.gov. We checked the bibliographies of included studies and any relevant systematic reviews. Our systematic review included randomized clinical trials (RCTs) conducted in people who had SCD without VOEs at trial entry. Eligible trials compared a single or combination treatment regimen (with each treatment classified as a conventional or nonconventional antiplatelet agent) with conventional care, placebo, or another regimen. No restrictions were placed on the route of administration, dose, frequency, or duration of treatment. We selected RCTs, assessed the risk for bias, and extracted data in a duplicate and independent fashion. We estimated risk ratios for dichotomous outcomes and mean differences for continuous outcomes. We also subjected our analyses to a random-effects model, and Trial Sequential Analysis (TSA) was used. We used the grading of recommendations, assessment, development, and evaluation (GRADE) approach to assess the overall quality of data for each individual outcome.
Results: We identified 5 RCTs (N=747) that met our criteria. Of these, 4 trials were multicenter and multinational. The trials included patients of all ages and assessed prasugrel, ticagrelor, crizanlizumab, and aspirin vs either placebo or no intervention. The most frequent route of administration was oral. The trials were small and carried a high risk for bias, given that pharmaceutical companies sponsored 4 of them. None of the trials reported information on quality of life. No meta-analysis was performed owing to heterogeneity in the ages of the participants and in the interventions. No single trial showed evidence of certainty regarding all-cause mortality. One trial showed uncertainty in comparing prasugrel vs placebo for preventing VOEs in patients younger than 18 years (relative risk [RR], 0.92; 95% CI, 0.80 to 1.06; low quality of evidence). TSA for this outcome suggested that a new trial should be conducted. One trial found a difference in the size effect of uncomplicated VOEs, favoring high-dose crizanlizumab vs placebo (mean difference, -1.50; 95% CI, -2.61 to -0.39; very low quality of evidence). No difference in VOEs was found in studies that compared either ticagrelor in children or prasugrel in adults vs placebo. The overall incidence of harms in any intervention did not differ from that in the control.
Conclusions: The current evidence does not support or reject the use of any antiplatelet agent for preventing VOEs in people with SCD. This conclusion was based on small RCTs that carried a high risk for bias. No conclusive evidence exists regarding relevant clinical outcomes because the evidence is limited and of very low quality.