“…Folate and vitamin B12 were detected via chemiluminescence immunoassays in three studies [15,22,28], radioimmunoassays in four studies [23,24,25,30], ELISA in two studies [26,31], a specific immunochemical method in one study [29], and the IMx assay in one study [16]. Three studies did not include the mean age of patients and controls [15,16,23], and one study included the median age of patients and controls [23]. Of the 12 included studies, six studies were conducted in Asia [15,22,24,26,28,31], four in Europe [16,23,25,30], one in America [27], and one in Africa [29].…”