title: Which is better? Guy's versus S.T.O.N.E. nephrolithometry scoring systems in predicting stone-free status post-percutaneous nephrolithotomy.
abstract: OBJECTIVE
  The aim of the present study was to compare the accuracy of the Guy's and S.T.O.N.E. scoring systems in predicting percutaneous nephrolithotomy (PCNL) outcomes.
  
  
  METHODS
  After obtaining ethics approval, medical records of patients undergoing PCNL between 2009 and 2013 at a tertiary stone center were retrospectively reviewed. Guy's and S.T.O.N.E. scoring systems were calculated. Regression analysis and ROC curves were performed.
  
  
  RESULTS
  A total of 185 PCNLs were reviewed. The overall stone-free rate was 71.9 % with a complication rate of 16.2 %. When compared to patients with residual fragments, stone-free patients had significantly lower Guy's grade (2.7 vs. 2; p < 0.001) and S.T.O.N.E. score (8.3 vs. 7.4; p = 0.004). Logistic regression analysis showed that both Guy's and S.T.O.N.E. systems were significantly associated with stone-free status, OR 0.4 (p < 0.001), and OR 0.7 (p = 0.001), respectively. Furthermore, both scoring systems were significantly associated with the estimated blood loss (p = 0.01 and p = 0.005). There was good correlation between both scoring systems and operative time (r = 0.3, p < 0.001 and r = 0.4, p < 0.001) and length of hospital stay (r = 0.2, p = 0.001 and r = 0.3, p < 0.001). However, there were no significant associations between both scoring systems and complications (p = 0.7 and p = 0.6). There was no significant difference in the areas under the curves for the Guy's and S.T.O.N.E. scoring systems (0.74 [95 % CI 0.66-0.82] vs. 0.63 [95 % CI 0.54-0.72]; p = 0.06).
  
  
  CONCLUSIONS
  Both Guy's and S.T.O.N.E scoring systems have comparable accuracies in predicting post-PCNL stone-free status. Other factors not included in either scoring system may need to be incorporated in the future to increase their accuracy.
authors: Division of Urology, McGill University Health Centre, 687 Pine Ave. West, Suite S6.92, Montreal, QC, H3A 1A1, Canada.|Department of Urology, Benha University Hospital, Benha University, Benha, Egypt.
authors: Yasser A
authors: YA
authors: Noureldin
authors: Division of Urology, McGill University Health Centre, 687 Pine Ave. West, Suite S6.92, Montreal, QC, H3A 1A1, Canada.|Department of Urology, Suez Canal University, Ismailia, Egypt.
authors: Mohamed A
authors: MA
authors: Elkoushy
authors: Division of Urology, McGill University Health Centre, 687 Pine Ave. West, Suite S6.92, Montreal, QC, H3A 1A1, Canada. sero.andonian@muhc.mcgill.ca.
authors: Sero
authors: S
authors: Andonian
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D035843:Biomedical Research / Q000379:methods*; D018572:Disease-Free Survival; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007669:Kidney Calculi / Q000175:diagnosis / Q000601:surgery*; D007902:Length of Stay; D008297:Male; D008875:Middle Aged; D009403:Nephrostomy, Percutaneous / Q000379:methods*; D061646:Operative Time; D011184:Postoperative Period; D011379:Prognosis; D012372:ROC Curve; D012107:Research Design; D012189:Retrospective Studies; D012720:Severity of Illness Index; D014057:Tomography, X-Ray Computed; D055815:Young Adult
keywords: Percutaneous nephrolithotomy; Renal calculi; Scoring method