A new method for the quantification of β-glucan in plasma and its application in the diagnosis of postoperative infection

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Abstract
In order to correctly diagnose and treat severe postoperative infections, it may be critical to detect and differentiate between endotoxin derived from Gram-negative bacteria and/or β-glucan derived from fungi. In addition to the chromogenic assay, the turbidimetric kinetic assay has been performed for the quantification of endotoxin in plasma usingLimulus amebocyte lysate as previously reported. However, it is also known that β-glucan triggers the coagulation ofLimulus amebocyte lysate. In the present study, the differentiation of β-glucan from endotoxin and its clinical application were studied. Endotoxin was able to be inactivated in plasma using one-tenth dilution by 10 per cent ethanol or distilled water, followed by heating at 100°C for 120 min, without affecting the activity of coexisting β-glucan. The treated sample was then subjected to the turbidimetric kinetic assay using Toxinometer ET-201®. Using this method, as little as 30 pg/ml of β-glucan in the plasma may be assayed separately, with the amount of circulating β-glucan in the plasma of normal subjects being less than 50 pg/ml. On the other hand, in patients with a fungal infection, the amount of β-glucan in their plasma was elevated significantly. Clinically, β-glucanemia may often occur in severe postoperative infection even if fungi are not detected.