Popiolek M. et al., 2023: Finding the optimal candidate for shock wave lithotripsy: external validation and comparison of five prediction models.
Department of Urology, Faculty of Medicine and Health, Örebro University, 701 85, Örebro, Sweden. .
Department of Radiology, Faculty of Medicine and Health, Örebro University, Örebro, Sweden.
Department of Urology, Faculty of Medicine and Health, Örebro University, 701 85, Örebro, Sweden.
Department of Clinical Sciences, Division of Infection Medicine, Lund University, Lund, Sweden.
Department of Urology Helsingborg Hospital, Helsingborg, Sweden.
We aimed to externally validate five previously published predictive models (Ng score, Triple D score, S3HoCKwave score, Kim nomogram, Niwa nomogram) for shock wave lithotripsy (SWL) single-session outcomes in patients with a solitary stone in the upper ureter. The validation cohort included patients treated with SWL from September 2011 to December 2019 at our institution. Patient-related variables were retrospectively collected from the hospital records. Stone-related data including all measurements were retrieved from computed tomography prior to SWL. We estimated discrimination using area under the curve (AUC), calibration, and clinical net benefit based on decision curve analysis (DCA). A total of 384 patients with proximal ureter stones treated with SWL were included in the analysis. Median age was 55.5 years, and 282 (73%) of the sample were men. Median stone length was 8.0 mm. All models significantly predicted the SWL outcomes after one session. S3HoCKwave score, Niwa, and Kim nomograms had the highest accuracy in predicting outcomes, with AUC 0.716, 0.714 and 0.701, respectively. These three models outperformed both the Ng (AUC: 0.670) and Triple D (AUC: 0.667) scoring systems, approaching statistical significance (P = 0.05). Of all the models, the Niwa nomogram showed the strongest calibration and highest net benefit in DCA. To conclude, the models showed small differences in predictive power. The Niwa nomogram, however, demonstrated acceptable discrimination, the most accurate calibration, and the highest net benefit whilst having relatively simple design. Therefore, it could be useful for counselling patients with a solitary stone in the upper ureter.
Urolithiasis. 2023 Apr 7;51(1):66. doi: 10.1007/s00240-023-01444-4.PMID: 37027057
The clinical value of different predictive nomograms for the outcome of SWL can be questioned. And there are indeed too many nomograms in the literature. This situation probably is unique for treatment of patients with urinary tract stones.
Based on results obtained and reported following SWL, it is well recognized that stone size, stone hardness (HU), to some extent the degree of hydronephrosis, and SSD are important determinants for SWL success or failure. Therefore, it should not come as a surprise that the two nomograms comprising most of these variables were the best. It was already known that triple-D score was inferior to a later presented quadruple-D score in which a factor for stone location was added.
The authors concluded that the Niwa-nomogram was most useful for patient counselling, but that other methods should be considered for future studies. Such a step probably is of little value, because the best way to select patients for SWL is to apply accumulated clinical experience. Without inclusion of operator skill, every nomogram will come short. Moreover, SWL results are highly dependent on the attention to every technical detail in the SWL procedure.