Luminometric assays of seven acute-phase proteins in minimal volumes of serum, plasma, sputum, and bronchioalveolar lavage.

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Abstract
We describe immunoluminometric assays for seven acute-phase proteins, which can be determined in minimal volumes of plasma, serum, sputum, and bronchioalveolar lavage. The theoretical volume of serum or plasma required to measure all seven analytes in duplicate is 130 nL, although in practice the smallest volume of sample was enough to fill a hematocrit tube (about 25 microL of blood), collected from neonates by the heel-prick method. The assays could be performed with 10 microL of sputum or with 100 microL of bronchioalveolar lavage. We measured alpha 1-antitrypsin, alpha 2-macroglobulin, alpha 1-acid glycoprotein, thyroxin-binding prealbumin, C-reactive protein, and total and secretory immunoglobulin A. The assays are rapid enough for all results to be returned to the ward on the same day and are suitable for monitoring neonatal sepsis. All coefficients of variation, derived from compound precision profiles, were less than 7% for clinically relevant analyte concentrations. Correlation with commercially available nephelometric assays was good.