Plasma lactoferrin in patients with neutropenia.

This study examines the role of plasma lactoferrin in the assessment of neutropenia. In particular, we have studied lactoferrin as an inhibitor of granulopoiesis and as an indicator of the size of the total blood granulocyte pool (TBGP). Plasma lactoferrin concentration was determined in a heterogeneous group of 30 patients with neutropenia. Serial plasma lactoferrin levels in a patient with cyclic neutropenia correlated with the cycles of the neutrophil count. Patients with splenomegaly had a grossly elevated lactoferrin:neutrophil ratio. Most chronic idiopathic neutropenia patients had no real clinical problems and a normal plasma lactoferrin level. The results provide further evidence to support the concept that plasma lactoferrin indicates the size of the TBGP and the lactoferrin: neutrophil ratio indicates the degree of granulocyte margination. There was no evidence to suggest that lactoferrin acting as a feedback inhibitor of granulopoiesis caused neutropenia in these patients.