If it's not broken, don't fix it

EDITOR—Rushton et al suggest that reference ranges for men should be used to assess iron status in women of childbearing age.1 They do, however, make some incorrect assumptions and do not consider the practical implications of such a change.

Women must have sufficient iron stores to prevent iron deficiency from menstrual blood loss or pregnancy. However, one in 150 people in the United Kingdom are homozygous for the C282Y mutation of the HFE gene, which is associated with haemochromatosis.2 Although the clinical penetrance of this genotype is low, widespread measures to increase the intake of iron in younger women will also increase the intake of men and postmenopausal women. It is therefore important that any changes in lower limits of indices of iron status are firmly supported by clinical and experimental evidence.

Rushton et al are incorrect in assuming that different lower limits for ferritin are used for detecting iron deficiency in young men and women. Although reference ranges (95%) in healthy young adults differ—for example, 35-220 µg/l for men and 9-136 µg/l for women2—the limit for iron deficiency used by clinicians is around 15 µg/l for both men and women, a value originally established by determining the highest value found in patients with iron deficiency anaemia.3

The national dietary and nutritional survey reported a median value for haemoglobin concentration in British women of childbearing age of 132 g/l. Increasing the lower cut-off point to 130 g/l, as used for men, would therefore define half the premenopausal adult female population of the United Kingdom as anaemic. Zhu and Haas found …