Objective: To externally validate Guy's stone score system and estimate its predictive accuracy.
Patients and methods: An analysis of 282 consecutive patients, who underwent a percutaneous nephrolithotomy, was performed. The association between Guy's stone score and several pre-, intra-, and postoperative parameters was assessed. A univariate and multivariate analysis was conducted to identify the independent predictors for stone-free rates. Area under the curve was used for predictive accuracy estimation.
Results: Stone burden, multiple stone locations, number of stones, number of implicated caliceal groups, and Guy's stone score were significantly associated with stone-free outcomes. The multivariate analysis showed that Guy's stone score, number of stones, and number of implicated caliceal groups are independent predictors of stone-free status. Receiver operating characteristic curve analysis revealed a significant predictive accuracy for the Guy's stone score.
Conclusions: The present study externally validated Guy's stone score. Significant predictive ability combined with great predictive accuracy was found.