Endogenous lysozyme inactivation in EMIT-dau assays

Though extraction is probably the best method to remove interfering endogenous lysozyme activity, other methods have been suggested. Micropore filtering, 65 degrees C heat treatment and methanol precipitation, or a combination of these methods are ineffective. Heating urine samples to 85 degrees C for 30 minutes removed endogenous lysozyme activity, but unpredictably alters the responsiveness of the various drugs of abuse urine assays. It cannot be recommended for removal of endogenous lysozyme activity for all EMIT immunoassays in urine.