Cyanide-Nitroprusside Colorimetric Assay: A Rapid Colorimetric Screen for Urinary Cystine
| Autor: | Callen D. Giesen, Dimitar Gavrilov, Clayton T. Brady, John C. Lieske, Robin S. Chirackal, Nikolay Voskoboev, Ryan M. Flanagan |
|---|---|
| Rok vydání: | 2017 |
| Předmět: |
0301 basic medicine
Detection limit chemistry.chemical_classification Creatinine Chromatography Reabsorption 030232 urology & nephrology Cystine General Medicine Cystinuria Tandem mass spectrometry medicine.disease Standard curve 03 medical and health sciences chemistry.chemical_compound 030104 developmental biology 0302 clinical medicine chemistry medicine Thiol |
| Zdroj: | The Journal of Applied Laboratory Medicine. 2:55-64 |
| ISSN: | 2475-7241 2576-9456 |
| DOI: | 10.1373/jalm.2016.022582 |
| Popis: | Background Cystinuria is an autosomal recessive disorder resulting in poor proximal tubule reabsorption of cystine in the nephron, increasing the risk of cystine stone formation. A fast, inexpensive assay to screen for urinary cystine is needed because cystine stones are difficult to noninvasively differentiate from more common calcium-containing ones. Tandem mass spectrometry (MS/MS) is sensitive and specific but is labor-intensive and costly. Alternatively, a colorimetric assay is fast and cost-effective; however, creatinine interference is an issue. Methods A published cyanide-nitroprusside colorimetric assay was modified for a high-throughput microplate format. Creatinine interference was reduced using 0.1 mol/L PBS and a standard reaction time of 60 s and was further corrected using a formula derived from the slope of multiple creatinine standard curves. Results The limit of blank was determined to be 2.6 mg/L, the limit of detection 11.9 mg/L, and the limit of quantitation 15.3 mg/L. The analytic measurement range was established as 15.3–100 mg/L cystine. Intraassay and interassay CV was calculated to be 9.6% and 8.0%, respectively, for a high-level cystine concentration (83.6 mg/L). Low-level cystine (36.4 mg/L) intraassay and interassay CV was determined to be 18.1% and 17.6%, respectively. Passing–Bablok regression analysis of colorimetric vs LC-MS/MS results revealed a slope of 1.10 and y intercept of −7.14 mg/L, with an overall bias of 2% by Bland–Altman plot analysis. Conclusions We analytically validated a rapid colorimetric assay suitable to quantify urinary cystine. The effect of thiol drugs on this assay remains to be determined. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|