Inter-observer variability amongst surgeons and radiologists in assessment of Guy's Stone Score and S.T.O.N.E. nephrolithometry score: A prospective evaluation

Aneesh Srivastava; Priyank Yadav; Kumar Madhavan; Sanjoy K Sureka; Uday P Singh; Rakesh Kapoor; M S Ansari; Hira Lal; Prabhakar Mishra

doi:10.1080/2090598X.2019.1703278

Inter-observer variability amongst surgeons and radiologists in assessment of Guy's Stone Score and S.T.O.N.E. nephrolithometry score: A prospective evaluation

Arab J Urol. 2019 Dec 18;18(2):118-123. doi: 10.1080/2090598X.2019.1703278.

Authors

Aneesh Srivastava¹, Priyank Yadav¹, Kumar Madhavan¹, Sanjoy K Sureka¹, Uday P Singh¹, Rakesh Kapoor¹, M S Ansari¹, Hira Lal², Prabhakar Mishra³

Affiliations

¹ Department of Urology and Renal Transplantation, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India.
² Department of Radiology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India.
³ Department of Biostatistics, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India.

Abstract

Objective: (a) To assess the inter-observer variability amongst surgeons performing percutaneous nephrolithotomy (PCNL) and radiologists for the Guy's Stone Score (GSS) and S.T.O.N.E. (stone size [S], tract length [T], obstruction [O], number of involved calyces [N], and essence or stone density [E]) nephrolithometry score; (b) To determine which scoring system of the two is better for predicting the stone-free rate (SFR) after PCNL.

Patients subjects and methods: Patients undergoing PCNL between February 2016 and September 2016 were prospectively enrolled. Preoperative computed tomography was done in all patients. The GSS and S.T.O.N.E. nephrolithometry score were independently calculated by eight surgeons and four radiologists. The patients were operated on by one of the surgeons (all were consultants). The Fleiss' κ coefficient was used to assess agreement independently between the surgeons and radiologists. Receiver operating characteristic (ROC) curves were constructed for predicting the SFR using the average of the scores of the surgeons and radiologists separately.

Results: A total of 157 patients underwent PCNL. The SFR was 71.3% (112/157 patients). The Fleiss' κ scores ranged from 0.51 to 0.88 (overall 0.79) for the S.T.O.N.E. score and 0.53-0.91 for the GSS, suggesting moderate to very good agreement. The ROC curve for the S.T.O.N.E. nephrolithometry scores of surgeons (area under the curve [AUC] = 0.806) as well as the radiologists (AUC = 0.810) had a higher predictive value for the SFR than the GSS of the surgeons (AUC = 0.738) and the radiologists (AUC = 0.747).

Conclusion: There is overall good agreement between surgeons and radiologists for both the GSS and S.T.O.N.E. nephrolithometry score. The S.T.O.N.E. score had a higher predictive value for the SFR than the GSS.

Abbreviations: AUC: area under the curve; GSS: Guy's Stone Score; KUB: kidneys, ureters and bladder; NCCT: non-contrast CT; PCNL: Percutaneous nephrolithotomy; ROC: receiver operating characteristic; SFR: stone-free rate; S.T.O.N.E.: stone size [S], tract length [T], obstruction [O], number of involved calyces [N], and essence or stone density [E].

Keywords: Guy’s Stone Score; Inter-observer variability; S.T.O.N.E. nephrolithometry score.