Method for the quantitative determination of proteinase inhibitors

A method for a quantitative determination of active and inactive proteinase inhibitors in a bodily fluid which comprises the steps of:

• a. obtaining a sample of a bodily fluid from a subject;
• b. preparing a first plurality of serial dilutions of the fluid of decreasing concentration;
• c. incubating the dilutions with varying concentrations porcine pancreatic elastase (PPE) and monitoring the catalytic activity which decreases linearly in relation to the dilutions of the fluid to a minimum point, after which the catalytic activity increases in relation to the dilution of the fluid;
• d. by means of regression analysis calculating the coordinates of the intersection of two linear lines, one of which is formed by the fluid concentration and the other by residual catalytic activity;
• and
• e. calculating the active and inactive proteinase inhibitor activity by computer-fit least squares regression analysis and comparing with a standard curve.