BACKGROUND: Recommendations on the optimal preservation of 24 h urine for the metabolic work-up in urolithiasis patients are very heterogeneous. In case two such tests with different storage condition recommendations are being analysed, multiple collections would be needed, challenging especially elderly and very young patients. We therefore aimed to evaluate the stability of urine constituents under different storage conditions. MATERIAL AND METHODS: We collected urine samples from ten healthy volunteers and prepared aliquots to be stored either at room temperature or 4 °C. Some aliquots were preserved using hydrochloric acid prior to storage, some thereafter, some using the BD Urine preservation tube and some were not preserved at all. Storage duration was 0, 24, 48 or 72 h. In all samples calcium, magnesium, phosphorus, creatinine, oxalate, citrate and uric acid were measured and compared to the according reference sample. RESULTS: We could not find any significant deviation for any of the analytes and preanalytical treatment conditions compared to the associated reference sample. CONCLUSION: Preservation of 24 h urine for the metabolic evaluation in stone formers might not be necessary for sample storage up to 72 h.

Clinical Department of Laboratory Medicine University Hospitals Leuven Leuven Belgium

Clinical Department of Laboratory Medicine University Hospitals Leuven Leuven Belgium; Department of Cardiovascular Sciences KU Leuven Leuven Belgium

Department of Clinical Biochemistry and Pharmacology The Tomas Bata Hospital in Zlín Havlíčkovo nábřeží 600 76275 Zlín The Czech Republic

Department of Laboratory Medicine Paracelsus Medical University Salzburg Austria

Department of Urology Barmherzige Brüder Hospital Salzburg Austria

Institute for Laboratory Medicine and Medical Microbiology Medizet München Klinik Munich Germany

Institute of Molecular Regenerative Medicine Paracelsus Medical University Salzburg Austria; Spinal Cord Injury and Tissue Regeneration Center Salzburg Paracelsus Medical University Salzburg Austria

UT SPSS Statistics Hallein Austria

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