White cell cystine

Description: 
White cell cystine content is measured by liquid chromatography tandem mass-spectrometry (LC-MS/MS). The cystine value is indexed to the white cell protein content, which is determined spectrophotometrically using the Biuret and bicinchoninic acid reaction, to give the final white cell cystine concentration. Preparation of a white cell pellet from whole blood samples, is required prior to analysis.

This test is not currently included in the laboratory's UKAS scope of accreditation to ISO15189:2022
Clinical details: 
Cystinosis, or nephropathic cystinosis, is an autosomal recessive lysosomal storage disorder, which usually presents in the first 6-12 months of infancy with generalised proximal tubular dysfunction. Confirmation of elevated white cell cystine is essential for diagnosis, and for monitoring of cysteamine treatment in known cystinosis patients.
Related condition or disease: 
Cystinosis (infantile nephropathic form, juvenile nephropathic form, and adult ocular non-nephropathic form).
Reference range: 

Wild type homozygotes <0.3 nmol ½ cystine per mg protein. Heterozygote carriers for cystinosis 0.3 - 1.0 nmol ½ cystine per mg protein. Homozygous cystinosis >1.0 nmol ½ cystine per mg protein. For patients on cysteamine/cystagon, target range is <1, assuming that the dose-sample interval is 5-12 hours.

Synonyms or keywords: 
White cell cystine, leucocyte cystine, leukocyte cystine, cystine in white blood cells
Department: 
Genetics Department
Location: 
Guy's Hospital
St Thomas' Hospital
Sample type and Volume required: 
Lithium heparin whole blood, minimum volume of 3 mL required.
Turnaround time: 
2 weeks
Special sample instructions: 

Samples must be kept at ambient temperature. Please do NOT separate, spin, refrigerate or freeze samples. 

For patients taking cysteamine, please provide the dose of last cysteamine (in mg), and the date and time of last dose cysteamine.

Criteria for acceptance / rejections of sample
Storage and transport: 
Samples must be kept at ambient temperature (do not refrigerate/freeze), and must be received at the Biochemical Genetics laboratory less than 30 hours after collection/venesection.
Contacts:
Biochemical Genetics Laboratory at Guy's Hospital
Genetics Department
Tower Wing - 5th Floor
Guy's Hospital
Great Maze Pond
London SE1 9RT

T: 020 7188 2591/2592
F: 020 7188 7275
E: ViapathBiochemicalGenetics@gstt.nhs.uk
For clinical advice or interpretation of results, please contact the laboratory in the first instance.
Laboratory: 
Biochemical Genetics Laboratory at Guy's

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Last updated: 14/11/2025