Development and Clinical Evaluation of Immunoluminometric Assays for Lactoferrin and Elastase-α1-Proteinase Inhibitor Complexes in Body Fluids with Special References to Bronchoalveolar Lavage and Neonatal Sepsis

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Abstract
Immunoluminometric assays for lactoferrin and elastase-.alpha.1-proteinase inhibitor complexes were developed using solid-phase methodology, which has already been published from this laboratory. The aim of the study was to develop a rapid method to see whether elevated granulocyte activity was present in the lung, as for example in neonatal sepsis. The lactoferrin assay gave reliable results within 30 minutes, the elastase-.alpha.1-proteinase inhibitor complexes, within 5 hours. The correlation between both analytes was good, so that the lactoferrin assay could replace the elastase-.alpha.1-proteinase inhibitor assay in emergency cases. The lactoferrin assay was used for rapid answer, the elastase-.alpha.1-proteinase inhibitor complex assay for "fine" monitoring of the progress of the disease. Both assays could be used to measure concentrations in plasma or bronchoalveolar lavage using a 10 .mu.l sample. Plasma for the elastase-.alpha.1-proteinase inhibitor complex determination had to be diluted 1:50 before being assayed. Only EDTA plasma was used in the assay, as either heparin plasma or serum resulted in granulocyte destruction, thus giving rise to elevated, and non-reproducible results. The results from bronchoalveolar lavage show an excellent correlation between elastase-.alpha.1-proteinase inhibitor complexes and lactoferrin. No interference was seen from lipaemic or icteric plasma samples. Results from haemolytic samples i.e. where lysis of erythrocytes and leukocytes had occurred, had to be treated with care if no clinical indication of intravascular haemorrhage was present. The assays lend themselves to perinatal diagnosis, as the total volume of plasma or lavage needed is theoretically under 50 .mu.l, i.e. ethically acceptable for regular monitoring of neonates. As far as could be determined, both assays were specific and robust. The elastase-.alpha.1-proteinase inhibitor immunoliminometric assay correlated well with the commercial ELISA test kit in EDTA plasma (ELISA = (0.93 .times. ILMA) - 41, n = 52, r = 0.93), showing that both assays measured similar complexes.