The concentration of free and conjugated 3-hydroxyanthranilic acid in the urine of bladder tumour patients before and after therapy, measured with an enzymatic method.

The basal concentration of the tryptophan metabolite 3-hydroxyanthranilic acid (3OHA), which has carcinogenic properties, was measured with an enzymatic method of determination which allowed separate measurement of free and conjugated 3OHA. The concentration of free 3OHA in untreated bladder cancer patients was significantly (P <0·001) higher than in a healthy control group, but after local therapy the concentration was significantly lower than before treatment (P <0·01). The concentration of conjugated 3OHA was nearly constant in the three groups.