Validation of the S.T.O.N.E. Score for Predicting Stone-Free Rate in Patients with Ureteral Stones Undergoing Semirigid Pneumatic Ureteral Lithotripsy
Description
We conducted a retrospective study of 266 patients with ureteral stones who underwent ULT at IBB University Hospitals in Yemen, between April 2021 and September 2023. The S.T.O.N.E. score was calculated based on factors obtained from preoperative non-contrast computed tomography scans. A nomogram was created to predict the likelihood of SFR failure post-ULT.
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**Study Design:** A retrospective study at IBB University hospitals included 266 patients with ureteral stones who underwent semirigid pneumatic ureterolithotripsy (ULT) from April 2021 to September 2023. The study was approved by the IBB University ethics committee and conducted per the Helsinki Declaration. Due to its retrospective design, patient consent for chart review was not required. All data were anonymized. **Inclusion Criteria:** Adult patients (≥18 years) with ureteral calculi who had preoperative non-contrast computed tomography (CT-KUB) and subsequently underwent semirigid pneumatic ULT were included. **Exclusion Criteria:** Exclusions were made for patients with ureteral anatomical anomalies, active urinary tract infections, lack of preoperative CT-KUB images, pregnant women, and those with acute renal failure. **Sample Size:** The sample size was determined using G Power version 3 software, requiring at least 255 patients to ensure statistical significance, accounting for a 5% dropout rate based on prior studies reporting an overall success rate (SFR) of 80.5%. **S.T.O.N.E. Score:** The S.T.O.N.E. score utilized preoperative CT-KUB characteristics—size, topography, obstruction, number of stones, and HU—scored on a 1–3 point scale, indicating greater complexity and lower SFRs. Scores ranged from 5 to 15 points, with 186 samples allocated for training and 80 for testing. **Main Outcome:** The primary outcome assessed the S.T.O.N.E. score's utility in predicting SFR failure for semirigid pneumatic ULT, while secondary outcomes included identifying predictive factors for SFR failure. **Statistical Analysis:** Data were analyzed using IBM SPSS version 22. Continuous variables were reported as means with standard deviations, and categorical variables as frequencies and percentages. Independent t-tests and Mann-Whitney tests were applied as appropriate. Chi-square tests evaluated categorical variables. Univariate and multivariate logistic regression analyses determined predictors of SFR failure with a significance threshold of p < 0.05. A receiver operating characteristic (ROC) curve analyzed the S.T.O.N.E. score, establishing predictive performance metrics including the area under the curve (AUC) and corresponding sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). The optimal S.T.O.N.E. score point was defined by the maximum Youden index value.