Davis Reaction

DAVIS REACTION (Davis) in malignant tumors, a color reaction of urine from patients with malignant tumors, published by the American D. in 1913. To 100 cm³ of fresh urine, 10 cm³ of pure hydrochloric acid is added, the mixture is heated to the beginning of boiling, then after cooling, 15 cm³ of sulfuric ether is added to the mixture, after which it is left for 16-24 hours, shaking several times. The results of the reaction are determined by the color of the urine, the ether, and the color of the precipitate formed after evaporation of the ether, determining the result as negative (ether pale), unclear (ether yellow), weakly positive (ether pale pink), positive (ether pink), and sharply positive (ether bright red). The chemical mechanism of the reaction has not yet been clarified. It is believed that the resulting pigment is close to hematoporphyrin. D. in cases of cancer or sarcoma never had a negative reaction result. Verification of the D. reaction by a number of authors gave positive results in cancer patients: from 73.4% (Vasiliev) to 83.8% (Rostock) and even up to 93% (Ragosa). At the same time, this reaction is also positive in other diseases (liver diseases, malaria, various hematurias) in 17.5% (Korzon), which significantly depreciates it as a diagnostic method.