Comparison of Different Methods for Measuring Urinary Oxalate and Citrate: An Observational Study

This observational study aims to compare three different laboratory methods for measuring urine oxalate and citrate concentrations. The primary objective is to evaluate whether an improved High-Performance Liquid Chromatography (HPLC) method-using a novel derivatization reagent-can achieve similar accuracy to the gold standard Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) while offering advantages in cost, speed, and ease of use in routine clinical settings.

The study will involve the collection of morning urine samples from both healthy volunteers and patients with urolithiasis (urinary stones). Each urine sample will be tested using the following three methods:

1. Modified High-Performance Liquid Chromatography (HPLC): This method builds on traditional HPLC technology by incorporating a novel derivatization reagent to enhance the sensitivity and accuracy of detecting oxalate and citrate. The improved HPLC method is designed to be less time-consuming and more cost-effective, which could make it a viable option for regular clinical use. 2. Ion Chromatography (IC): Widely used in many hospital laboratories, the IC method detects urine oxalate and citrate without the need for a derivatization step. While this method is straightforward and convenient, its sensitivity and accuracy are expected to be lower compared to LC-MS/MS and the modified HPLC method. 3. Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS): LC-MS/MS is currently considered the gold standard for measuring urine oxalate and citrate due to its high sensitivity and specificity. However, the method requires expensive equipment and involves complex procedures, limiting its routine application in most clinical laboratories.

Participants will provide urine samples, which will be divided and analyzed using all three methods simultaneously. The study will assess the correlation and consistency between the methods, with a particular focus on comparing the modified HPLC method to LC-MS/MS. Statistical analyses, including Bland-Altman analysis and linear regression, will be used to determine the agreement between the measurement techniques.

This study is non-interventional and involves only the collection of urine samples, posing minimal risk to participants. Informed consent will be obtained from all participants after they are fully briefed about the study objectives, procedures, and any potential risks. All collected data will be managed confidentially and analyzed rigorously to ensure the reliability of the findings.

If the modified HPLC method demonstrates comparable accuracy to LC-MS/MS, it could provide a more accessible, cost-effective, and timely option for routine clinical measurement of urinary oxalate and citrate. Such an improvement in laboratory diagnostics may support better clinical decision-making in the prevention and management of urinary stone disease, ultimately benefiting patient care.