[Laboratory diagnosis of cystinuria]

Delayed diagnosis, apparently due to insufficient knowledge of partly simple methods of cystine determination and their practical application, is often a particular problem in the treatment of cystine lithiasis. The present paper gives a survey of a variety of laboratory methods to determine cystine in the urine both qualitatively and quantitatively. Their applicability in various diagnostic situations is discussed. In clinico-chemical routine, colorimetric cystine determinations using Brands test, but partibularly the nickel/dithionite reagent, is an established and reliable laboratory method. Possibilities of its use as quick screening assays are described.