Creatinine in urine – a method comparison. Issue 10 (3rd March 2017)

• Record Type: Journal Article
• Authors: Luginbühl, Marc; Weinmann, Wolfgang
• Is Part Of: Drug testing and analysis. Volume 9:Issue 10(2017)
• Page Start: 1537
• Page End: 1541
• Publication Date: 2017-03-03
• Subjects: creatinine -- urine analysis -- drug testing -- point‐of‐care testing -- urine manipulation; Drugs -- Analysis -- Periodicals; Drug testing -- Periodicals; Chemistry, Forensic -- Periodicals; 615.1901
• DOI: 10.1002/dta.2166
• Languages: English
• ISSNs: 1942-7603

Abstract

Abstract : Drug screening in urine is widely applied in forensic toxicology. Contrary to blood analysis, excessive or reduced fluid intake can substantially alter the concentration of substances in urine. As a standard to detect urinary dilution, creatinine concentrations are analyzed. A sample with a concentration below 20 mg/dL is generally defined as too diluted to provide a valid result in abstinence control samples. This work investigates the potential of three different methods for the determination of creatinine concentrations in urine samples: A ZIC®‐HILIC‐based liquid chromatography–tandem mass spectrometry (LC–MS/MS) method, a spectrophotometric method on an AU 480 chemistry system, and a portable, chemical‐reaction‐based, point‐of‐care testing device were compared by measuring 200 urine samples. When comparing the two laboratory methods, LC–MS/MS and spectrophotometry, a mean difference of 3.7 ± 14 mg/dL was found, indicating that the spectrophotometric method slightly overestimates the creatinine concentration. When comparing the LC–MS/MS method with the point‐of‐care testing device, a mean concentration difference within the calibration range for POCT (>20 mg/dL (excluding 16 samples) and <500 mg/dL (excluding 4 samples)) of 21 ± 37 mg/dL was found, indicating that the point‐of‐care testing device overestimates the measured creatinine concentration. A point‐of‐care testing device as used during this study can provide valuable information for on‐site analysis. However, reported concentrations above 500 mg/dL should be further evaluated, for example by dilution of the sample. Copyright © 2017 John Wiley & Sons, Ltd. Abstract : Three different methods for the determination of creatinine concentrations in urine are carefully investigated. LC–MS/MS proved to be advantageous compared to a spectrophotometric or point‐of‐care testing based analysis method.