Abstract: A method of assay for an enzyme catalysing the release of long chain fatty acids or, conversely, for an ester substrate for such enzymes is applicable to clinical samples and comprises removing substantially all the albumin from the clinical sample, incubating the sample after albumin removal with, for enzyme assay, an ester substrate or, for substrate assay, the enzyme, under conditions effective to release a fatty acid, causing the fatty acid to bind to a fatty acid binding protein and assaying the binding of the fatty acid to the binding protein.

Abstract: A method of quantitative assay for a substrate such as triglyceride capable of undergoing enzymatic hydrolysis to release long chain fatty acids in an albumin-containing clinical sample comprises incubating the albumin-containing clinical sample with an enzyme such as lipase which acts upon the substrate to be assayed under conditions effective to release fatty acid therefrom, causing the fatty acid thus released to bind to a fatty acid binding protein (FABP) and assaying the binding of the fatty acid to the FABP.