B-037 Configuration and validation of urine oxalate open channel assay on the Roche Cobas c503

Abstract Background Measuring urine oxalate is crucial for diagnosing hyperoxaluria, evaluating kidney stone risk, monitoring patients at risk for oxalate-related kidney injury and guiding their treatment plans. The objective of this study was to evaluate the performance characteristics of Trinity Biotech urine oxalate kit configured on a Roche cobas c503 analyzer. The validation followed Clinical Laboratory Standards Institute (CLSI) recommendations. Methods Assays parameters were modified based on reagent instructions for use recommendations where available (Trinity Biotech Product No. 591-D) to optimize the analytical performance on Roche cobas c503. Reagent preparation was modified to minimize the wastage due to dead volume requirements on the Roche cobas development channel cartridges (Cat No. 08463166190). The assay parameters were configured using the Roche cobas development channel file creator software. Precision was evaluated by running 3 replicates of 2 quality controls (QC) daily across 5 days. Correlation studies were performed by comparing Roche cobas c503 results to Roche cobas c502 (N=40) and Abbott Architect ci4100 (N=13) using patient urine samples. Linearity was assessed using a series of samples made via mixing of a concentrated high QC and water that spanned the analytical measuring range. Limit of detection (LoD) was determined by 6 replicates of a low concentration specimen. All patient samples were deidentified. Result Precision studies demonstrated acceptable performance with coefficient of variations of 1.68% and 0.72% for the low and high QC respectively. Correlation between the Roche cobas c502 and c503 was excellent (r = 0.9998, slope = 1.02, intercept = -5.90 µmol/L). An additional comparison study between Roche cobas c503 and Abbott Architect ci4100 shows an excellent correlation (r=0.9996; slope = 0.9963, intercept = 6.6219 µmol/L). Linearity studies demonstrated a linear assay up to concentrations of 2000 µmol/L. The LoD was determined to be 2.9 µmol/L. Conclusion We successfully established an assay configured on a Roche cobas c503 for urine oxalate analysis. The assay showed a robust performance and was found to be acceptable for use of patient testing.