Cystine in white cells

Chemical Pathology

Notes

• White cell cystine levels are measured for the diagnosis and monitoring of treatment of cystinosis, a rare autosomal recessive lysosomal storage disease.
  
• Cystinosis is characterised by accumulation of the amino acid cystine in lysosomes leading primarily to renal damage (Fanconi syndrome) and retinopathy.
  
• There are three distinct types of cystinosis with slightly different presentations.
  
• Cystinosis is usually treated with cysteamine to reduce build up of cystine levels.
  

Sample requirements

Essential to contact the duty biochemist at least 24 hours before sample collection as timing of sampling and transport arrangements have to be made in advance due to the limited stability of this analyte.

For patients on cysteamine treatment samples should be collected 5-6 hours post dose.

For adults, 6 ml of blood taken into a lithium heparin tube

For children, a minimum of 3 ml of lithium heparin blood is required.

Storage/transport

Do not store. Sample should be sent immediately to the laboratory for urgent transport to the assaying laboratory.

Required information

Relevant clinical details including whether for diagnosis or for monitoring, and time of sample collection relative to last dose of cysteamine.

Turnaround times

The samples are sent by courier to Great Ormond Street Hospital, with results expected back within 8 weeks.

Reference ranges

• Less than 0.3 1/2 cyst/mg ptn (nmol of half cystine per mg protein)
  
• For samples collected 5 - 6 hours post cysteamine levels should be less than 1 1/2 cyst/mg ptn
  
• Haemodialysis decreases cysteamine levels but not white cell cystine.
  

Further information

To learn more access Genetics Home Reference - Cystinosis

Page last updated 23/02/2015