Maria C Sighinolfi et al., 2024: External validation of a nomogram for outcome prediction in management of medium-sized (1-2 cm) kidney stones

Maria C Sighinolfi 1, Tommaso Calcagnile 1 2, Marco Ticonosco 2, Shaniko Kaleci 3, Stefano DI Bari 2, Simone Assumma 1, Luca Sarchi 1, Enrico Panio 1 2, Riccardo Ferrari 2, Adele Piro 2, Alberto Ragusa 4, Silvia Ciarlariello 5, Rodrigo D DA Silva 6, Roberto LA Rocca 7, Ester Illiano 7, Alessio Paladini 8, Francesco Persico 9, Davide Giraudo 10, Enrico DE Marzo 11, Riccardo Grisanti 12, Guglielmo Mantica 13, Esteban Emiliani 14, Massimo Madonia 15, Michele Salvetti 16, Pierfrancesco Bassi 17, Emanuele Montanari 18, Pierluigi Bove 19, Alchiede Simonato 20, Timothy D Averch 21, Francesco Porpiglia 22, Alessandro Calarco 23, Sebastiano Bruschetta 24, Fabio Manferrari 25, Francisco P Daels 26, Maria A Cerruto 27, Alessandro Antonelli 27, Giorgio Mazzon 28, Antonio Celia 28, Claudio Simeone 29, Stefano Zaramella 10, Alberto Saita 9, Elisabetta Costantini 8, Ettore Mearini 8, Mauro DE Dominicis 23, Vincenzo Mirone 7, Fernando J Kim 6, Stefania Ferretti 2, Stefano Puliatti 2, Bernardo Rocco 1, Salvatore Micali 30
1Department of Urology, ASST Santi Paolo e Carlo, Milan, Italy.
2Department of Urology, University of Modena and Reggio Emilia, Modena, Italy.
3Clinical and Experimental Medicine (CEM), Department of Surgical, Medical, Dental and Morphological Sciences with Interest in Transplant, Oncology and Regenerative Medicine, University of Modena and Reggio Emilia, Modena, Italy.
4Department of Urology, Campus Biomedico University of Rome, Rome, Italy.
5Department of Urology, Morgagni-Pierantoni Hospital, Forlì, Forlì-Cesena, Italy.
6Department of Urology, Denver Health Medical Center, Denver, CO, USA.
7Department of Urology, University of Naples Federico II, Naples, Italy.
8Department of Urology, University of Perugia, Perugia, Italy.
9Department of Urology, IRCCS Humanitas Research Hospital, Rozzano, Milan, Italy.
10Department of Urology, Ospedale degli Infermi, Biella, Italy.
11Department of Urology, Regional Health Care and Social Agency Civil Hospitals of Brescia, Brescia, Italy.
12Department of Urology, Nuovo Ospedale Civile, Sassuolo, Modena, Italy.
13Department of Urology, San Martino Research Hospital, Genoa, Italy.
14Department of Urology, Fundació Puigvert, Autonomous University of Barcelona, Barcelona, Spain.
15Department of Urology, Urologic Clinic, University Hospital of Sassari, Sassari, Italy.
16Department of Urology, Azienda ULSS8 Berica, Arzignano, Vicenza, Italy.
17Department of Urology, Agostino Gemelli University Hospital, Rome, Italy.
18Department of Urology, Polyclinic of Milan, Milan, Italy.
19Department of Urology, San Carlo of Nancy Hospital, Rome, Italy.
20Department of Surgical, Oncological and Stomatological Disciplines, University of Palermo, Palermo, Italy.
21Department of Urology, Prisma Health Midlands, Columbia, SC, USA.
22Department of Urology, San Luigi Gonzaga Hospital, University of Turin, Orbassano, Turin, Italy.
23Christ's Hospital, Rome, Italy.
24Casa di Cura San Camillo, Messina, Italy.
25Department of Urology, Ramazzini Hospital, Carpi, Modena, Italy.
26Department of Urology, Italian Hospital of Buenos Aires, Buenos Aires, Argentina.
27Department of Urology, Integrated University Hospital of Verona, Verona, Italy.
28Department of Urology, Civil Hospital of Bassano, Bassano del Grappa, Vicenza, Italy.
29Department of Urology, University of Brescia, Brescia, Italy.
30Department of Urology, University of Modena and Reggio Emilia, Modena, Italy

Abstract

Background: Stone nomogram by Micali et al., able topredict treatment failure of shock-wave lithotripsy (SWL), retrograde intrarenal surgery (RIRS) and percutaneous nephrolithotomy (PNL) in the management of single 1-2 cm renal stones, was developed on 2605 patients and showed a high predictive accuracy, with an area under ROC curve of 0.793 at internal validation. The aim of the present study is to externally validate the model to assess whether it displayed a satisfactory predictive performance if applied to different populations.

Methods: External validation was retrospectively performed on 3025 patients who underwent an active stone treatment from December 2010 to June 2021 in 26 centers from four countries (Italy, USA, Spain, Argentina). Collected variables included: age, gender, previous renal surgery, preoperative urine culture, hydronephrosis, stone side, site, density, skin-to-stone distance. Treatment failure was the defined outcome (residual fragments >4 mm at three months CT-scan).

Results: Model discrimination in external validation datasets showed an area under ROC curve of 0.66 (95% 0.59-0.68) with adequate calibration. The retrospective fashion of the study and the lack of generalizability of the tool towards populations from Asia, Africa or Oceania represent limitations of the current analysis.

Conclusions: According to the current findings, Micali's nomogram can be used for treatment prediction after SWL, RIRS and PNL; however, a lower discrimination performance than the one at internal validation should be acknowledged, reflecting geographical, temporal and domain limitation of external validation studies. Further prospective evaluation is required to refine and improve the nomogram findings and to validate its clinical value.

Minerva Urol Nephrol. 2024 Aug;76(4):484-490. doi: 10.23736/S2724-6051.24.05672-6. Epub 2024 May 10. PMID: 38727672