With the normal primer set, a blue color solution indicating a positive reaction was observed after amplification of genomic DNA from a normal subject (αα/αα), SEA trait (--SEA/αα) and THAI trait (--THAI/αα), while the solution turned colorless (no amplification) when Hb Bart’s hydrops fetalis DNA (--SEA /--SEA) was used as the genomic material (Fig. 2A). Here, GSTM1 is linked to hydrops fetalis.