title: Calcium oxalate crystallization index (COCI): an alternative method for distinguishing nephrolithiasis patients from healthy individuals.
abstract: Urinary supersaturation triggers lithogenic crystal formation. We developed an alternative test, designated calcium oxalate crystallization index (COCI), to distinguish nephrolithiasis patients from healthy individuals based on their urinary crystallization capability. The effect of urine volume, oxalate, phosphate, citrate, potassium, and sodium on COCI values was investigated. COCI values were determined in 24-hr urine obtained from nephrolithiasis patients (n=72) and matched healthy controls (n=71). Increases in urine oxalate and phosphate and decreases in urine volume and citrate resulted in significantly increased COCI values. The urinary COCI in nephrolithiasis patients was significantly higher than that in healthy individuals. Two healthy subjects who had elevated COCI values were found to have asymptomatic kidney calculi. The receiver operating characteristic analysis showed an area under the curve of the urinary COCI test of 0.9499 (95%CI: 0.9131-0.9868) for distinguishing between nephrolithiasis and healthy subjects. At the cutoff of 165 mg oxalate equivalence/day, the urinary COCI test provided sensitivity, specificity, and accuracy amounts of 83.33%, 97.18%, and 90.21%, respectively. Urinary COCI values were primarily dependent on urine volume, oxalate, and phosphate. The test provided high sensitivity and specificity for clinically discriminating nephrolithiasis patients from healthy controls. It might be used to detect individuals with asymptomatic kidney calculi.
authors.affiliation: Department of Biochemistry, Faculty of Medicine, Chulalongkorn University, Bangkok.
authors.forename: Bowei
authors.initials: B
authors.lastname: Yang
authors.affiliation: Department of Biochemistry, Faculty of Medicine, Chulalongkorn University, Bangkok.
authors.forename: Thasinas
authors.initials: T
authors.lastname: Dissayabutra
authors.affiliation: Division of Urology, Sunpasit Prasong Hospital, Ubon Ratchathani Province.
authors.forename: Wattanachai
authors.initials: W
authors.lastname: Ungjaroenwathana
authors.affiliation: Department of Biochemistry, Faculty of Medicine, Chulalongkorn University, Bangkok.
authors.forename: Piyaratana
authors.initials: P
authors.lastname: Tosukhowong
authors.affiliation: Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok.
authors.forename: Monpichar
authors.initials: M
authors.lastname: Srisa-Art
authors.affiliation: Department of Biological Science, Faculty of Science, Ubon Ratchathani University, Ubon Ratchathani Province, Thailand.
authors.forename: Thavorn
authors.initials: T
authors.lastname: Supaprom
authors.affiliation: Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok.
authors.forename: Numpon
authors.initials: N
authors.lastname: Insin
authors.affiliation: Department of Biochemistry, Faculty of Medicine, Chulalongkorn University, Bangkok chanchai.b@chula.ac.th.
authors.forename: Chanchai
authors.initials: C
authors.lastname: Boonla
mesh_terms: D002129:Calcium Oxalate / Q000652:urine*; D003460:Crystallization; D006801:Humans; D053040:Nephrolithiasis / Q000175:diagnosis*; D012372:ROC Curve; D012015:Reference Standards; D012680:Sensitivity and Specificity; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D002129:Calcium Oxalate
keywords: COCI; calcium oxalate crystallization index; diagnosis; kidney stone; nephrolithiasis