Prepared by Alice A. Greene, Ph.D.
Photography: Francis Schanberger
Date: October 1998
The proper preparation of white blood cells for cystine analysis is essential for the diagnosis and management of cystinosis. Let me explain why this is.
Cystinosis is an inherited metabolic disease in which the free amino acid, cystine, accumulates in every cell which has lysosomes. The kidneys are severly affected leading to the need for a kidney transplant. A therapeutic treatment (Cystagon) has been developed, which depletes cells of the accumulated cystine. To preserve kidney funtion the patients must be maintained on a proper dose of Cystagon. In order to know whether the dose is appropriate and whether the patient is taking this foul-tasting medicine, we monitor the cystine level in white blood cells. We use blood because it is relatively easy to obtain, but we must separate the white blood cells because they, and not the red cells, contain lysosomal cystine. In this disease, the serum concentration of cystine in normal.
We depend upon you, the local laboratory personnel, to prepare the white cells from your patients and send the frozen, acid-stablized pellet to us for analysis. The quality of the preparation affects the results of our assay. To help with training for this white cell preparation, we have produced this short manual. It's easy once you get the knack.
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