GSTM1 and pulmonary arterial hypertension: The Hb values following blood transfusions were corrected by decreasing the elevation in Hb level that was measured following blood transfusion; control [mean 0.9 ± 1 g/dl (median 0.7 g/dl, IQR 0.2–1.3 g/dl), occult PPH 2 ± 1.4 g/dl (1.7, 1–2.8 g/dl)] and overt PPH [3.2 ± 1.8 g/dl (3.2, 1.8–4.4 g/dl), p < 0.0001].