A solid-phase radioimmunoassay for the measurement of lactoferrin in human plasma: variations with age, sex, and disease.

A solid-phase radioimmunoassay is described for measuring lactoferrin levels in normal human plasma. The sensitivity of the assay was 6 ng. per milliliter with an intraassay coefficient of variation of 4 per cent and an interassay value of 9 per cent. Healthy adult males had a mean plasma level of 1.62 mug per milliliter which was significantly higher than adult females, 1.07 mug per milliliter. Postmenopausal females had levels similar to men, 1.74 mug per milliliter, while younger women had a significantly lower mean value, 0.75 mug per milliliter. Two menstruating women and 2 pregnant women had moderately elevated levels. Consistently elevated levels were found in patients with untreated or relapsing chronic myeloid leukemia--all over 12.0 mug per milliliter, while patients on marrow suppressant therapy tended to have subnormal levels. The collection of serum specimens as opposed to plasma, resulted in inconsistently elevated levels: EDTA was the anticoagulant of choice, as heparin interfered in the radioimmunoassay system.