Simplified photometric copper-soap method for rapid assay of serum lipase activity

We modified the method of Yang and Biggs [Clin. Chem. 17, 512 (1971)] for greater speed and simplicity. Serum is incubated with an emulsified olive oil substrate, the fatty acids extracted, the copper soap formed, and phases separated, all in a single tube. An aliquot of the organic phase is removed for color development. One analysis can be completed in 35 min, 20 in less than 2 h. The method is accurate and precise. Results correlate well with the unmodified colorimetric method, and with the classical titrimetric lipase procedure. The reference interval (normal range) is 20 to 180 U/liter.