Abstract:Objective: To carry out an external validation of the modified S.T.O.N.E. nephrolithometry scoring system, and to evaluate its effectiveness in predicting the stone-free rate (SFR) of flexible ureteroscopic lithotripsy (FURL). Methods: Clinical data of 396 patients with nephrolithiasis undergoing FURL from May 2018 to October 2021 were collected, and the modified S.T.O.N.E. nephrolithometry scoring system was evaluated. The correlation of modified S.T.O.N.E. nephrolithometry scoring system scores and each variables with one-phase SFR was analyzed. The receiver operating characteristic curve (ROC) was computed to estimate the value of the predictive models, and Hosmer-Lemeshow goodness-of-fit test was used to examine the calibration of the prediction models. Results: All 396 cases of FURL operation were performed successfully, and the one-phase SFR was 76.8%. The median of the modified S.T.O.N.E. nephrolithometry scoring system score was 6 (4 to 12) in this cohort. The modified S.T.O.N.E. nephrolithometry scoring system score showed significant correlation with the postoperative SFR of FURL (OR=6.627, 95%CI=3.620-12.131, P=0.001). The area under curve of ROC in the state of stone clearance after FURL operation was 0.778 (95%CI=0.723-0.834). Hosmer-Lemeshow goodness-of-fit test showed that the modified S.T.O.N.E scoring system had satisfactory calibration in predicting SFR (χ2=0.824, P=0.844). Conclusion: The modified S.T.O.N.E. nephrolithometry scoring system can accurately predict postoperative stone-free status of FURL, and provide assistance in pre-operative evaluation and clinical decision-making.
