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ID:995 White Cell Cystine
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DescriptionUsed in the monitoring and diagnosis of cystinosis, which is characterised by early renal impairment, polyuria, polydypsia,failure to thrive, fanconi syndrome, etc. Cystinosis is NOT the same disease as cystinuria (a cause of renal stones).
Indication Diagnosis and monitoring of cystinosis
Additional InfoHeterozygotes are phenotypically normal. Homozygotes usually present around 1-2 years old with polyuria, polydypsia, failure to thrive, rickets and Fanconi syndrome (generalised aminoaciduria with phoshaturia and glycosuria). They are treated with Cystagon which reduces lysosomal cystine accumulation and thereby preserves e.g renal function. Therapeutic ranges < 2.0 nmol 1/2 cystine/mg protein is adequate with < 1.0 nmol 1/2 cystine/mg protein being ideal. If untreated renal failure ensues.
Concurrent Testsna
Dietary Requirementsna
InterpretationNote: Results between 1-2 nmol 1/2 cystine/mg protein may still be consistent with cystinosis. Note overlap between heterozygote and homozygote reference ranges.

DepartmentSpecialist Laboratory Medicine
Tube Picture
Collection Conditions All samples must be received within 24 hrs of venepuncture and between Mon 9AM to Friday 2pm. Monitoring uses trough levels.
Min. Vol 3mL

Ref. Range (Male) See note
Ref. Range (Female)
Ref. Range (Paed)
Ref. Range Notes Normal < 0.5 nmol 1/2 cystine/mg protein Heterozygote < 1.0 nmol 1/2 cystine/mg protein Homozygote cystinosis usually > 2.0 nmol 1/2 cystine/mg protein.
Units - Not Defined -
IP Acute TAT- Not Defined -
IP Routine TAT28 days
GP Acute TAT- Not Defined -
GP Routine TAT28 days
Turnround CommentNA

Originally edited by : CE. Review due on 03/05/2020 10:51:34. Published By RB on 03/05/2019 10:51:34.