Ferrokinetics and erythropoiesis in man: an evaluation of ferrokinetic measurements.

The plasma iron clearance half-time and plasma iron turnover have usually been interpreted as measures of total erythroid activity and the red-cell utilization of 59Fe has been equated with effective red-cell production. Erythrocyte iron turnover has sometimes been calculated as the product of plasma iron turnover and percentage utilization. We have assessed these measurements as estimates of erythroid activity by comparing them with total marrow iron turnover and red-cell iron turnover determined by the method of Ricketts et al (1975) in 10 normal subjects and 51 patients with an uncomplicated haematological disorder. The results show that the plasma iron clearance half-time does not reflect erythroid activity and that plasma iron turnover can be particularly misleading in patients with reduced marrow activity. Red-cell utilization and erythrocyte iron turnover give a distorted reflection of effective erythropoiesis except in patients with erythroid hypoplasia. Marrow iron turnover and red-cell iron turnover provide more realistic and generally applicable assessments of the degree and effectiveness of erythroid activity.