In which of the following laboratory tests would you expect to find the greatest disparity in reference intervals between men and (non-pregnant) women?
High-Yield Explanation
Men have higher reference intervals than women in tests related to iron and hemoglobin (Hb) concentration in blood. The normal reference interval for Hb concentration in women is lower (12.0-16.0 gm/dL) than that for men (13.5-17.5 gm/dL) due to lower serum testosterone levels (testosterone is higher in men and stimulates erythropoiesis) and blood loss during menses. Fuhermore, women normally have about 400 mg of iron (as ferritin) in their bone marrow iron stores versus an average of 1000 mg of iron for men. In the absence of inflammation, the small circulating fraction of ferritin correlates well with ferritin stores in the bone marrow. Hence, men have different reference intervals for serum ferritin than do women (15-200 ng/mL in men versus 12-150 ng/mL in women). The mean corpuscular volume, serum alkaline phosphatase, serum glucose, and serum sodium are similar in both sexes. Ref: Beutler E. (2010). Chapter 42. Disorders of Iron Metabolism. In J.T. Prchal, K. Kaushansky, M.A. Lichtman, T.J. Kipps, U. Seligsohn (Eds), Williams Hematology, 8e.