Role of Fourier transform infrared (FT-IR) spectroscopy in the evaluation of urinary stone disease

Nephrolithiasis is a common disease occurring in both industrialized and developing countries and mainly affecting adults aged 20-60 years. The determination of crystalline and molecular composition and the quantification of all stone components are helpful to establish the etiology of urinary stone disease. Different methodologies exist for the analysis of renal stones. In our laboratory, we used the chemical spot test, which is the most popular method for routine stone analysis. However, this method is relatively inaccurate and does not allow distinguishing between the crystalline phases. In this paper, we evaluated the quantitative FT-IR spectroscopy technique for a possible introduction in our laboratory. We analyzed 100 urinary stones, divided into 3 groups: pure stones, mixed stones, and pure stones with substances in trace. Results of each group were compared with those obtained with chemical spot test. A total or partial disagreement between the two methods was observed in 59% of pure stones, in 86.6% of mixed stones and in 100% of pure stones with substances in trace, respectively, suggesting the replacement of the chemical test with FT-IR spectroscopy.