External Validation and Evaluation of Reliability and Validity of the Triple D Score to Predict Stone-Free Status After Extracorporeal Shockwave Lithotripsy.

OBJECTIVE: The Triple D scoring system is defined as novel and simple nomogram using the main parameters (skin-to-stone distance, stone density, and volume) to indicate most appropriate patients for extracorporeal shockwave lithotripsy (SWL). We aimed to evaluate the accuracy of the Triple D scoring system in predicting SWL success rates.

PATIENTS AND METHODS: In two tertiary academic centers, charts were retrospectively analyzed of patients who had, between January 2014 and May 2016, been treated by SWL for radiopaque kidney stones. A total of 200 patients were enrolled into the study. Parameters were calculated for each of the three specified variables. Since one point was assigned for any parameter that was less than the cutoff value, Triple D scores ranged from 0 (worst) to 3 (best).

RESULTS: Stone-free status was achieved in 115 patients (57.5%), and 85 patients had one or more residual fragments (42.5%). Differences in stone characteristics, including stone location, density, and volume, were statistically significant in patients whether SWL achieved stone-free status or not (p < 0.001, p < 0.001, and p < 0.001, respectively). Triple D scores were significantly higher in patients treated with SWL compared with patients in whom SWL failed (p < 0.001). Triple D scores of 0, 1, 2, and 3 correlated with stone-free rates of 41.7%, 33.7%, 69.4%, and 97%, respectively. The multivariate analyses revealed that Triple D score and stone location were identified as independent factors affecting SWL success (p < 0.001 and p = 0.008, respectively). The mean number of SWL sessions was significantly higher in patients with SWL failure (p = 0.003).

CONCLUSION: Our study externally validates that the Triple D scoring system is associated with SWL success in the treatment of renal and ureteral stones. Further studies are warranted to assess clinical usefulness and the accuracy of this nomogram in different patient groups.