White blood cell (WBC) cystine level tests are used to monitor treatment with cystine-depleting therapy (CDT).1 The prescribed CDT dosage may be adjusted based on WBC cystine levels rather than renal function.1 There are 2 WBC cystine testing options, and each has a different target cystine level.2-4
WBC cystine level test | Target cystine level range |
---|---|
Granulocytes | Below 1.9 nmol 1⁄2 cystine/mg protein |
Mixed leukocytes | Below 1.0 nmol 1⁄2 cystine/mg protein |
The tests are not interchangeable, and the same test should be ordered each time for comparability.2-4
Testing kits are available at WBCKit.com.
1. Ariceta G, Camacho JA, Fernández-Obispo M, et al. Cystinosis in adult and adolescent patients: recommendations for the comprehensive care of cystinosis. Nefrología. 2015;35(3):304-321. 2. Elmonem MA, Veys KR, Soliman NA, van Dyck M, van den Heuvel LP, Levtchenko E. Cystinosis: a review. Orphanet J Rare Dis. 2016;11:47. Published April 22, 2016. 3. Langman CB, Barshop BA, Deschênes G, et al. Controversies and research agenda in nephropathic cystinosis: conclusions from a “Kidney disease: improving global outcomes” (KDIGO) controversies conference. Kidney Int. 2016;89(6):1192-1203. 4. Gertsman I, Johnson WS, Nishikawa C, Gangoiti JA, Holmes B, Barshop BA. Diagnosis and monitoring of cystinosis using immunomagnetically purified granulocytes. Clin Chem. 2016;62(5):766-772.