Children excluded a posteriori differed from those included: They were older (median age (IQR) 53 (12–155) versus 39 (6–141) months, p = 0.019), were less severely ill (median admission PRISM score 4 (0–6) versus 5 (2–9), p < 0.001), had less congenital heart disease (8.6% versus 23.1%, p < 0.001) and had a higher median Hb at PICU admission (122 (108–139) versus 110 (95–124) g/L, p < 0.001). The gene discussed is GSTM1; the disease is congenital heart disease.