External Validation and Evaluation of Reliability and Validity of the S-ReSC Scoring System to Predict Stone-Free Status after Percutaneous Nephrolithotomy |
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Authors: | Min Soo Choo Chang Wook Jeong Jae Hyun Jung Seung Bae Lee Hyeon Jeong Hwancheol Son Hyeon Hoe Kim Seung-june Oh Sung Yong Cho |
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Institution: | 1. Department of Urology, Seoul National University Hospital, Seoul, Korea.; 2. Department of Urology, Seoul National University Boramae Medical Center, Seoul, Korea.; Eberhard-Karls University, Germany, |
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Abstract: | ObjectivesThe Seoul National University Renal Stone Complexity (S-ReSC) scoring system was developed to predict the stone-free rate (SFR) after single-tract percutaneous nephrolithotomy (PCNL). This study is an external validation of this scoring system.Materials and methodsA retrospective review included 327 patients who underwent PCNL at 2 tertiary referral centers. The S-ReSC score was assigned from 1 to 9 based on the number of sites involved. The stone free status was defined as either complete clearance or clinically insignificant residual fragments <4 mm in size at 1 month follow-up imaging. Inter-observer and test-retest reliabilities were evaluated. The statistical performance of the prediction model was assessed by its predictive accuracy, predictive probability, and clinical usefulness.ResultsThe overall SFR was 65.4%. SFRs were 83.9%, 47.6%, and 21.4% in low (1–2), intermediate (3–4), and high (5–9) score groups, respectively, with significant differences (P<0.001). Inter-observer and test-retest reliabilities revealed almost perfect agreements. External validation of the S-ReSC scoring system revealed an AUC of 0.731 (95% CI 0.675–0.788). The AUC of 3-titered S-ReSC score groups was 0.691 (95% CI, 0.629–0.753). The calibration plot showed that the predicted probability of SFR had a concordance comparable to that of the observed frequency. The Hosmer–Lemeshow goodness-of-fit statistic revealed an adequate performance of the predictive model (P = 0.10). Inter-observer and test-retest reliability showed a good level of agreement.ConclusionsThe S-ReSC scoring system is useful in predicting the post-PCNL SFR and in describing the complexity of renal stones. |
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