title: Infrared vibrational spectroscopy: a rapid and novel diagnostic and monitoring tool for cystinuria.
abstract: Cystinuria is the commonest inherited cause of nephrolithiasis (~1% in adults; ~6% in children) and is the result of impaired cystine reabsorption in the renal proximal tubule. Cystine is poorly soluble in urine with a solubility of ~1 mM and can readily form microcrystals that lead to cystine stone formation, especially at low urine pH. Diagnosis of cystinuria is made typically by ion-exchange chromatography (IEC) detection and quantitation, which is slow, laboursome and costly. More rapid and frequent monitoring of urinary cystine concentration would significantly improve the diagnosis and clinical management of cystinuria. We used attenuated total reflection - Fourier transform infrared spectroscopy (ATR-FTIR) to detect and quantitate insoluble cystine in 22 cystinuric and 5 healthy control urine samples. Creatinine concentration was also determined by ATR-FTIR to adjust for urinary concentration/dilution. Urine was centrifuged, the insoluble fraction re-suspended in 5 μL water and dried on the ATR prism. Cystine was quantitated using its 1296 cm-1absorption band and levels matched with parallel measurements made using IEC. ATR-FTIR afforded a rapid and inexpensive method of detecting and quantitating insoluble urinary cystine. This proof-of-concept study provides a basis for developing a high-throughput, cost-effective diagnostic method for cystinuria, and for point-of-care clinical monitoring.
authors.affiliation: Glynn Laboratory of Bioenergetics, Institute of Structural and Molecular Biology, University College London, Gower Street, London WC1E 6BT, United Kingdom.
authors.forename: Katherine V
authors.initials: KV
authors.lastname: Oliver
authors.affiliation: Mass Spectrometry and Proteomics, Institute of Biosciences and Bioresources, National Research Council of Italy, Naples, Italy.
authors.forename: Annalisa
authors.initials: A
authors.lastname: Vilasi
authors.affiliation: Glynn Laboratory of Bioenergetics, Institute of Structural and Molecular Biology, University College London, Gower Street, London WC1E 6BT, United Kingdom.
authors.forename: Amandine
authors.initials: A
authors.lastname: Maréchal
authors.affiliation: UCL Centre for Nephrology, Royal Free Hospital, Pond Street, London NW3 2QG, United Kingdom.
authors.forename: Shabbir H
authors.initials: SH
authors.lastname: Moochhala
authors.affiliation: UCL Centre for Nephrology, Royal Free Hospital, Pond Street, London NW3 2QG, United Kingdom.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Unwin
authors.affiliation: Glynn Laboratory of Bioenergetics, Institute of Structural and Molecular Biology, University College London, Gower Street, London WC1E 6BT, United Kingdom.
authors.forename: Peter R
authors.initials: PR
authors.lastname: Rich
mesh_terms: D003404:Creatinine / Q000652:urine; D003555:Cystinuria / Q000175:diagnosis* / Q000652:urine; D057166:High-Throughput Screening Assays; D006801:Humans; D019095:Point-of-Care Systems; D012680:Sensitivity and Specificity; D017550:Spectroscopy, Fourier Transform Infrared / Q000191:economics / Q000379:methods*; D014556:Urine / Q000737:chemistry*
chemical_list: D003404:Creatinine