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Normal range: Negative

Comment: Urinary excretion of cystine is age –dependent. It is high in the first months then decreases thereafter. Elevated levels of cystine are found in cystinosis, cystinurias and the first trimester of pregnancy. Also, because cystine is relatively insoluble, precipitation of cystine results in the formation of calculi. Reduced levels are associated with sever burns

Sample: Spot urine or 24 hr urine