Plasma levels of the calcium-binding L1 leukocyte protein: standardization of blood collection and evaluation of reference intervals in healthy controls.

Release of the calcium-binding protein L1 from blood granulocytes in vitro was found to be strongly influenced by anticoagulants and was accelerated during blood clotting. EDTA effectively inhibited this release. The material of choice for obtaining base-line L1 levels in blood is, therefore, EDTA plasma. Care should be taken to avoid admixture with cells from the buffy coat. The reference interval for L1 concentrations in plasma was established by testing samples from 533 blood donors. The L1 distribution proved in both sexes to be log-normal. The reference interval in females was 90 to 530 micrograms/l, and in males 120 to 660 micrograms/l. A positive correlation was found between the L1 level and the white blood cell count (r = 0.46, p = 0.0001).