Inter-Observer Reliability and Reproducibility of CROES, Guy’s and STONE Nephrolithometry Scoring Systems for Predicting Percutaneous Nephrolithotomy Outcomes

Abstract

Objective: To assess inter-observer reliability and reproducibility of CROES, Guy’s and S.T.O.N.E. nephrolithometry scoring systems (NSS). Material and Methods: A total of 128 patients who underwent percutaneous nephrolithotomy (PNL) between January 2019 and January 2021 were included in the study. Calculation of the CROES, S.T.O.N.E, and Guy’s NSSs was made by three independent urologists with different academic levels. These were; a very experienced (>500 PCNL cases) endourologist (Rater 1), a urologist who had just finished (>100 PCNL cases) their urology education (Rater 2) and a 3rd year urology resident who had never performed a PCNL operation (Rater 3). All were blinded to the procedure outcomes. Results: An excellent correlation was found between three raters for Guy and S.T.O.N.E. scoring systems (kappa value 0.810-0.962). However, for the CROES score there is an excellent correlation between Rater 1 and Rater 2, but there were good correlations between Rater 1 vs Rater 3 and Rater 2 vs Rater 3 (kappa values 0.910 and 0.698-0.721 respectively). The highest correlation was between Rater 1 and Rater 2 for Guy score (kappa value 0.962) (Table 3). All intra-class correlations were statistically significant (p<0.001). The highest intra-class correlations were seen for the S.T.O.N.E. score (ICC: 0.980). Conclusion: The present study revealed that all three NSS frequently used in current urology practice have reproducible and reliable results. Additionally, we believe that the application of CROES NSS by more experienced clinicians will be effective in obtaining clearer results.