Lactoferrin in plasma measured by an ELISA technique: evidence that plasma lactoferrin is an indicator of neutrophil turnover and bone marrow activity in acute leukaemia.

This study describes an ELISA technique with high specificity, sensitivity, accuracy and reproducibility for measurements of plasma lactoferrin. The detection limit was 0.001 microgram/ml and the median value obtained in EDTA plasma from 47 healthy adults was 0.100 microgram/ml (0.05 fractile: 0.046 microgram/ml, 0.95 fractile: 0.257 microgram/ml). The lactoferrin concentration in serum was on the average 2 1/2 times higher than in plasma. The ambient temperature did not influence the plasma concentration during the first 6 h from blood sampling to separation of plasma from the cells. In 8 patients with untreated acute leukaemia plasma lactoferrin was positively correlated to the peripheral neutrophil count. An almost parallel course in plasma lactoferrin and peripheral neutrophil number was observed in 4 patients with AML during chemotherapy. In 2 patients achieving complete remission, plasma lactoferrin increased about 6 d before the concomitant increase in neutrophil count, suggesting plasma lactoferrin as an early predictor of bone marrow regeneration.