The Boehringer Mannheim cholesterol esterase/cholesterol oxidase/peroxidase/3,4-dichlorophenol kinetic reagent was modified by the inclusion of TBHBA (2,4,6-Tribromo-3-hydroxybenzoic acid) which reacts with hydrogen peroxide and 4-aminophenazone to produce a quinone-imine dye with a greater molar absorptivity than that produced with phenol.