Randomised trial of two strategies offering women mobile screening for breast cancer.

erythropoietin. Transferrin saturation is a good indicator of the current balance of supply and demand of plasma iron, although it is an inadequate indicator of the amount of iron stored. In addition, Bainton and Finch showed that once the transferrin saturation falls below 16% iron supply for erythropoiesis may be inadequate.4 Our data also suggest that, during treatment with erythropoietin, monitoring of transferrin saturation is more reliable for detecting functional iron deficiency than is monitoring of serum ferritin concentration. We believe that functional iron deficiency will become an increasing problem as treatment with erythropoietin is used more widely unless prophylactic iron is given parenterally when indicated-that is, when transferrin saturation falls below 20%. This iron supplementation should also optimise the cost effectiveness of the drug.