title: How practical is the application of percutaneous nephrolithotomy scoring systems? Prospective study comparing Guy's Stone Score, S.T.O.N.E. score and the Clinical Research Office of the Endourological Society (CROES) nomogram.
abstract: OBJECTIVE
  To prospectively compare the Guy's Stone Score (GSS), S.T.O.N.E. [stone size (S), tract length (T), obstruction (O), number of involved calices (N), and essence or stone density (E)] score and the Clinical Research Office of the Endourological Society (CROES) nephrolithometric nomogram to predict percutaneous nephrolithotomy (PCNL) success rate and assess the correlation with perioperative complications.
  
  
  METHODS
  We prospectively evaluated all consecutive PCNL patients at our institute between 1 November 2013 and 31 May 2015. The above scoring systems were applied to preoperative non-contrast computed tomography and the practical difficulties in such applications were noted. Perioperative complications and the stone-free rate (SFR) were also recorded. Receiver operating characteristic curves were drawn and the areas under curves were compared and appropriate statistical analysis done.
  
  
  RESULTS
  In all, 48 renal units were included in the study. The overall SFR was 62.2%. The presence of staghorn stones (β= 27.285, 95% confidence interval 1.19-625.35;P= 0.039) was the only significant variable associated with the residual stones on multivariate analysis. Stone-free patients had significantly lower median GSS (2 vs 4) and S.T.O.N.E. scores (6 vs 10) and higher median CROES scores (83% vs 63%) (allP< 0.001) compared to residual-stone patients. All scoring systems were significantly associated with SFR (allP< 0.001). There was no significant difference in the areas under curves of the scoring systems (0.858, 0.923, and 0.931, respectively). Furthermore, all scoring systems had weak correlations with Clavien-Dindo classified complications (r= 0.29,P= 0.045;r= 0.40,P= 0.005 andr= -0.295,P= 0.04, respectively). We found no standardisation for the measurement of stone dimensions, tract length, Hounsfield units, and staghorn definition.
  
  
  CONCLUSIONS
  All scoring systems equally predicted SFR and had a weak correlation with Clavien-Dindo complications. Standardisation is needed for the variables in which they have been found deficient.
authors.affiliation: Department of Urology, Postgraduate Institute of Medical Education and Research (PGIMER) and Dr. Ram Manohar Lohia Hospital, Baba Kharak Singh Marg, New Delhi, Delhi, India.
authors.forename: Anurag
authors.initials: A
authors.lastname: Singla
authors.affiliation: Department of Urology, Postgraduate Institute of Medical Education and Research (PGIMER) and Dr. Ram Manohar Lohia Hospital, Baba Kharak Singh Marg, New Delhi, Delhi, India.
authors.forename: Nikhil
authors.initials: N
authors.lastname: Khattar
authors.affiliation: Department of Urology, Postgraduate Institute of Medical Education and Research (PGIMER) and Dr. Ram Manohar Lohia Hospital, Baba Kharak Singh Marg, New Delhi, Delhi, India.
authors.forename: Rishi
authors.initials: R
authors.lastname: Nayyar
authors.affiliation: Department of Radio-diagnosis, Postgraduate Institute of Medical Education and Research (PGIMER) and Dr. Ram Manohar Lohia Hospital, Baba Kharak Singh Marg, New Delhi, Delhi, India.
authors.forename: Shibani
authors.initials: S
authors.lastname: Mehra
authors.affiliation: Department of Urology, Postgraduate Institute of Medical Education and Research (PGIMER) and Dr. Ram Manohar Lohia Hospital, Baba Kharak Singh Marg, New Delhi, Delhi, India.
authors.forename: Hemant
authors.initials: H
authors.lastname: Goel
authors.affiliation: Department of Urology, Postgraduate Institute of Medical Education and Research (PGIMER) and Dr. Ram Manohar Lohia Hospital, Baba Kharak Singh Marg, New Delhi, Delhi, India.
authors.forename: Rajeev
authors.initials: R
authors.lastname: Sood
keywords: 3D, three-dimensional; ACS, acute angle, complicated calyx and stone size; AUC, area under curve; BMI, body mass index; CCI, Charlson Comorbidity Index; CROES, Clinical Research Office of the Endourological Society; Clinical Research Office of the Endourological Society (CROES); GSS, Guy’s Stone Score; Guy’s Stone Score; HU, Hounsfield unit; IQR, interquartile range; KUB, plain abdominal radiograph of the kidneys, ureters and bladder; NCCT, non-contrast CT; PCNL, percutaneous nephrolithotomy; Percutaneous nephrolithotomy (PCNL); ROC, receiver operating characteristic; Renal stone; S.O.N., stone size, obstruction and number of involved calyces; S.T.O.N.E. score; S.T.O.N.E., stone size (S), tract length (T), obstruction (O), number of involved calices (N), and essence or stone density (E); SFR, stone-free rate; SFS, stone-free status; SPSS, Statistical Package for the Social Sciences; SSD, skin-to-stone distance; SWL, shockwave lithotripsy; US, ultrasonography