“…The database search identified 149 citations; as shown in our flowchart ( Figure 1 ), we finally considered 44 articles, 42 of which were full papers [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 ] plus one thesis [ 53 ] and one abstract [ 54 ] that examined the relationship between HC, MTHFR, and SCD and that were included in our systematic review and meta-analysis. In particular, Table 1 shows the studies that investigated plasma HC in SCD (22 case-control and 2 cohort studies), Table 2 shows the studies that investigated MTHFR TT and cystathionine beta synthase (all case-control), and Table 3 shows the studies that investigated the MTHFR TT genotype in relation to clinical features of SCD (all cohort studies).…”