10 - 14 days
White blood cell cystine
Leukocyte Cystine Shadow
Looking to order a test?
We’ve provided helpful links to make ordering easy.Find a Requisition
All specimens should be accompanied by a requisition.Submitting Specimens
Learn about how to properly label and where to ship specimens.Order Kits and Supplies
MLabs provides all the supplies necessary for the collection of specimens.Test FAQ
Visit our provider FAQ and learn about common questions to ordering tests.
Competitive protein binding assay.
The intracellular cystine content of acid-stabilized white blood cells may be used to evaluate the cystine-depleting effect of Cystagon or to diagnose (or rule out) new cystinosis patients. White cells are used because cystine is not elevated in red cells or plasma of cystinosis patients. (It is elevated in urine also, but this is not diagnostic.) The normal value is generally less than 0.2 nmol half cystine/mg white cell protein. The cystinosis value is generally greater than 2 nmol half cystine/mg white cell protein.
Interpretive report provided.
* Reference ranges may change over time. Please refer to the original patient report when evaluating results.
Contact MLabs Client Services Center prior to collection of specimen for instructions regarding sample preparation or to confirm that UMHS specimen processing tech will be available. Blood must be collected 5-6 hours after a dose of Cystagon and processed immediately for the white cell cystine measurements to be meaningful.