Comparison of Supersaturation Outputs from Different Programs and Their Application in Testing Correspondence with Kidney Stone Composition.

Introduction: Relative supersaturation (SS) for calcium oxalate (CaOx), calcium phosphate (CaP), and uric acid (UA) has been used for assessing urinary crystallization and estimated by programs, including EQUIL, Joint Expert Speciation System (JESS), and Lithorisk. We compared outputs from these programs and their correspondence with stone composition. Materials and Methods: SS of CaOx, CaP, and UA, using EQUIL, JESS, and Lithorisk were calculated from stone-forming patients. Pearson correlation coefficients were used to ascertain the correspondence between the outputs. Fractional regression models evaluated the relationship between SS and the percentage of each compound in the stones. Results: Two hundred eleven patients were included. Pearson correlation coefficients for CaOx ( r  ≥ 0.96), CaP ( r  ≥ 0.99), and UA SS ( r  ≥ 0.99) showed a high correspondence between all programs. We observed a significant correspondence between CaOx SS and the percentage of CaOx dihydrate in the stone ( p  < 0.001), as well as between the percentage of brushite and apatite and CaP SS. UA SS showed the strongest correspondence with the percentage of UA in the stones ( p  < 0.001). Conclusions: Good correlation between EQUIL, JESS, and Lithorisk was observed and good correspondence with stone composition. The magnitude of the association demonstrated by fractional regression models supports evidence for applying SS in clinical practice.