LCAT inhibitors interfere with the enzymatic determination of cholesterol and triglycerides

5,5-Dithiobis-(2-nitrobenzoic acid) (DTNB) and p-chloro-mercuriphenylsulfonic acid (PCMPS) are well-known sulfhydryl inhibitors that are used to inhibit lecithin: cholesterol acyltransferase (LCAT). They were each found to interfere with the enzymatic assays of cholesterol and triglycerides. DTNB falsely reduced the measured plasma cholesterol content, and falsely increased triglyceride readings. The interference with the triglyceride assay could be largely prevented by blanking for glycerol. PCMPS had only a slight effect on the cholesterol assay, but falsely lowered the triglyceride readings to a great extent, even with glycerol-blanking. Thus, these inhibitors should be avoided when plasma samples are to be enzymatically analyzed for cholesterol or triglycerides.