A modified technique for determining uric acid in blood and urine.

The methods most commonly used for the determination of uric acid are those of Benedict, Behre, and Folin described in almost all textbooks of clinical biochemical technique. The Folin method has been in use in this laboratory for some time, where uric acid determinations are often carried out three or four times a day on the same patient, but it was realized that this method was not sufficiently reliable to enable such repeated determinations to be carried out with accuracy. It was found that, using the same batch of reagents, the colour intensity produced varied from day to day, and even from one set of determinations to another, so that the preparation of a standard curve was impossible. At least two standard determinations had to be carried out in parallel with the tests in order to cover the usual working range of 2-10 mg.% of uric acid (in blood plasma). One of the chief causes of error seemed to be concerned with the boiling time, and it was therefore decided to find a method which would eliminate the necessity for boiling and be sufficiently constant in its results to enable us to prepare a standard curve. In a personal communication Dr. Wolfson, of the Michael Rees Hospital, Chicago, U.S.A., indicated a method for determining uric acid as used in his laboratory, and the modified technique outlined below is based upon this method.