Marrow fibrosis studied by ferrokinetics

Abstract

A 40-yr-old white male was admitted for evaluation of anemia. Physical examination revealed pallor and marked splenomegaly. Laboratory studies revealed Hb 7.5 g/dl, Hct 21%, WBC 19,000/cu mm, platelets 557,000/cu mm, and serum iron 225 pg/dl. Ferrokinetic studies (Fig. 1) disclosed: plasma iron disappearance t~/2 350 min; plasma iron turnover 0.25 mg/kg/day; maximum RBC incorporation 5%8% at day 5; liver>spleen>sacrum. A bone marrow biopsy revealed fibrous tissue with hypocellularity, erythroblastopenia, and tear-drop cells charasteristic of erythroid hypoplasia. Ferrokinetics testing is based on the incorporation of 59Fe into hemoglobin and subsequently into the forming erythrocytes. It provides information relating to the mechanisms of anemia and helps pinpoint a diagnosis of the hematologic disorder. Ferrokinetics study includes several indices: (1) plasma iron clearance (tl/2); (2) plasma iron turnover rate (rag/day) = [Plasma iron (mg/liter) • plasma volume (liters) • 0.693 • 1440] + Plasma iron clearance tl/2 (min); (3) maximum red blood cell incorporation of 59Fe = [(Maximum activity/ml whole blood + venous hematocrit) x Red cell mass (ml) x 100] + Total activity injected; (4) marrow:liver:spleen ratio; (5) whole body iron scan, when feasible. The performance of a ferrokinetics study requires the intravenous injection of 5-10 pCi of SgFe-ferrous citrate either directly or after incubation with 20-30 ml autologous plasma. An aliquot is kept for dose standardization. Blood samples are obtained at 0, 10, 30, 60, 120, 180, and 240 min after injection. Blood samples are