Table 2.

The strength and credibility of the previously discussed studies concerning traditional treatment options for SCD

Study ID	Study method	Strength and credibility
Gluckman et al., 201758	Observational and retrospective	The strength of the study is the large sample size with a long follow-up period, International collaboration which includes 106 centers in 23 countries, and comprehensive analysis. The limitations of the studies are retrospective study subject to selection bias, limited to HLA identical siblings transplant, heterogeneity of treatment protocols
Brazauskas et al., 202059	international, retrospective, registry-based survey	The study’s strengths include specific inclusion criteria and a large sample size with a long follow-up period. The limitations of the study are selection bias, reliance on registry-based data, and the potential of missing data.
Baronciani et al., 201660	retrospective non-interventional study	The strength of the data includes a large sample size with long follow-up and multicenter data and standardized data collection. The limitations of the study include variability in clinical practices, limited information on secondary transplants,
Pawlowska et al., 201861	retrospective observational study	The strength of the study includes innovative approach such as novel pretransplant immunosuppressive strategy (PTIS) combined with T cell–replete grafts and PTCY-based GVHD prophylaxis and detailed case analysis. The limitations of the study include a small sample size, a short follow-up period, and a single-center study.
Krishnamurti, 202162	Observational study	The strength of the study includes comprehensive data collection, relevance to clinical practice, and data from a diverse population. The limitations of the study include lack of a control group and Potential Socioeconomic and Regional Disparities.

GVHD, graft-versus-host-disease; HLA, human leukocyte antigen; PTCY, post transplantation cyclophosphamide; SCD, sickle cell disease.