Last reviewed 01/2018


  • plasma methionine and homocystine levels are elevated
  • homocystine is excreted in the urine
  • plasma cystine levels are reduced
  • positive urine cyanide-nitroprusside test

Urine or serum samples should be rapidly deproteinised prevent the formation of disulphide bonds between proteins and homocyst(e)ine.

Ref: Stantbury JB et al (1983). The Metabolic Basis of Inherited Disease, 5th edn. McGraw-Hill.