title: External validation and evaluation of reliability and validity of the S-ReSC scoring system to predict stone-free status after percutaneous nephrolithotomy.
abstract: OBJECTIVE
  The 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.
  
  
  METHODS
  A 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.
  
  
  RESULTS
  The 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.
  
  
  CONCLUSIONS
  The S-ReSC scoring system is useful in predicting the post-PCNL SFR and in describing the complexity of renal stones.
authors.affiliation: Department of Urology, Seoul National University Hospital, Seoul, Korea.
authors.forename: Min Soo
authors.initials: MS
authors.lastname: Choo
authors.affiliation: Department of Urology, Seoul National University Hospital, Seoul, Korea.
authors.forename: Chang Wook
authors.initials: CW
authors.lastname: Jeong
authors.affiliation: Department of Urology, Seoul National University Hospital, Seoul, Korea.
authors.forename: Jae Hyun
authors.initials: JH
authors.lastname: Jung
authors.affiliation: Department of Urology, Seoul National University Boramae Medical Center, Seoul, Korea.
authors.forename: Seung Bae
authors.initials: SB
authors.lastname: Lee
authors.affiliation: Department of Urology, Seoul National University Boramae Medical Center, Seoul, Korea.
authors.forename: Hyeon
authors.initials: H
authors.lastname: Jeong
authors.affiliation: Department of Urology, Seoul National University Boramae Medical Center, Seoul, Korea.
authors.forename: Hwancheol
authors.initials: H
authors.lastname: Son
authors.affiliation: Department of Urology, Seoul National University Hospital, Seoul, Korea.
authors.forename: Hyeon Hoe
authors.initials: HH
authors.lastname: Kim
authors.affiliation: Department of Urology, Seoul National University Hospital, Seoul, Korea.
authors.forename: Seung-June
authors.initials: SJ
authors.lastname: Oh
authors.affiliation: Department of Urology, Seoul National University Boramae Medical Center, Seoul, Korea.
authors.forename: Sung Yong
authors.initials: SY
authors.lastname: Cho
mesh_terms: D002138:Calibration; D003710:Demography; D005260:Female; D006801:Humans; D007669:Kidney Calculi / Q000473:pathology / Q000601:surgery*; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009403:Nephrostomy, Percutaneous / Q000379:methods*; D015588:Observer Variation; D015203:Reproducibility of Results; D012107:Research Design