A risk of inaccuracy in biochemical analysis of urinary stone-forming salts

We investigated the occasional inaccuracy in the biochemical measurement of urine by comparing the values from untreated samples to those obtained following our experimental pre-treatment regimen, which prevents precipitation and dissolves visible crystals. Discrepancies were observed between some of the paired samples, especially with regard to calcium and uric acid (urate) concentrations. Moreover, considerable differences were recognized in fresh as well as stored urine specimens. Our findings demonstrate the need to develop accurate methods of processing urine for biochemical analysis with multichannel autoanalyzers.