Characterization and elimination of a factor in serum that interferes with turbidimetry and nephelometry of lipase.

We studied a serum component ("pseudolipase") that interferes with both turbidimetric and nephelometric lipase measurements. Pseudolipase activity in serum was found in the presence of rheumatoid factor and in other disorders of active immune processes. The incidence of this interferent in sera seems to be greater than reported previously. We describe a method for eliminating its effect without affecting pancreatic lipase activity, by precipitating some of the proteins, including IgM, with polyethylene glycol.