In this model, decisions to administer ESA are made on a biweekly basis and follow a simple set of rules mimicking an anemia manager’s or a treatment algorithm’s decision pattern based on measured patient Hb levels (Fig 2): If the patient’s Hb is located within a defined target window (which we here set to 10–11 g/dL), the previously administered ESA dose is maintained. This evidence concerns the gene GSTM1 and anemia.