Test Overview
Test Methodology

Competitive protein binding assay.

Test Usage

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.

Reference Range *

Interpretive report provided.

Test Details
Days Set Up
Monday - Thursday
Analytic Time

10 - 14 days

Soft Order Code
MiChart Code
Cystine, Leukocytes (MMGL)
  • Cystine, Leukocytes
  • Cystine, Leukocyte
  • White blood cell cystine
  • Leukocyte Cystine Shadow
  • Leukocyte Preparation
Reference Laboratory
UCSD Cystine Determination Lab
Special Testing
Specimen Requirements
Collection Instructions

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.

Special Handling

Contact the MMGL laboratory at 734-615-2429 for instructions prior to collection of specimen.
Page 0603 immediately for sample pick-up by laboratory if at the UMHS hospital complex.

Normal Volume
5 mL whole blood
Minimum Volume
3 mL whole blood
Storage Temperature
Processing required prior. (F)frozen product.
Rejection Criteria
Sample not received within required time interval.
Additional Information

Test sent to University of California, San Diego, Department of Pediatrics, Cystine Determination Laboratory.

CPT Code
Fee Code
NY State Approved