A Simple Modified Method for Urine Citrate Determination
Rabia Şeker, Vildan Fidancı, Demokan Erol, Okan Yalbuzdağ, Gülsevim Saydam, Mehmet Şeneş, Doğan Yücel



Objective: Measurement of urine citrate is used to assess the risk of urinary stone formation. We attempted to perform a modified, cheap and reliable colorimetric method for the analysis of urinary citrate and to compare it with an enzymatic method.
Methods: Urine citrate levels were measured with a colorimetric method and a commercially available enzymatic method in patients with urolithiasis (n=50) and in healthy controls (n=44). We modified the colorimetric method which was first developed by Millan with a subsequent modification of Lewis. Performance characteristics of the methods were compared.
Results: Urine citrate levels of patients were lower as compared to controls by both of the methods. However, the difference between patients and controls was insignificant by enzymatic method, whereas significant by in-house method (P&��0.05). Within-run imprecisions for colorimetric method were 2.1%, 3.06% and 0.52% and 3.19%, 0.91% and 2.99% for enzymatic method in low, intermediate and high citrate containing urinary pools; between-day imprecisions of the methods were 11.16%, 14.74%, 9.36%, and 17.45%, 19.94%, 23.93% in the same pools, respectively. Both of the methods were linear up to 5 mmol/L. The detection limits of colorimetric and enzymatic methods were 0.19 mmol/L and 0.357 mmol/L; mean recoveries were 88.7% and 89.46%, respectively. The coefficient of correlation between the methods was r=0.922.
Conclusion: Colorimetric method is superior to the enzymatic method. Colorimetric method more efficiently detects lower urine citrate levels in urolithiasis patients and discriminates patients from controls.

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