Abstract: TH-PO1081

ROKS II Nomogram: Predicting Future Symptomatic Stone Episodes

Session Information

Category: Mineral Disease

  • 1204 Mineral Disease: Nephrolithiasis

Authors

  • Vaughan, Lisa E., Mayo Clinic, Rochester, Minnesota, United States
  • Enders, Felicity T., Mayo Clinic, Rochester, Minnesota, United States
  • Lieske, John C., Mayo Clinic, Rochester, Minnesota, United States
  • Vrtiska, Terri J., Mayo Clinic, Rochester, Minnesota, United States
  • Mehta, Ramila A., Mayo Clinic, Rochester, MN, Rochester, Minnesota, United States
  • Rule, Andrew D., Mayo Clinic, Rochester, Minnesota, United States
Background

We previously developed a prediction tool for symptomatic recurrence after the first stone event (ROKS nomogram). A more generalizable prediction tool is needed that can also be applied in stone formers with more than one prior stone episode.

Methods

We performed a population-based cohort study of validated incident kidney stone formers in Olmsted County, Minnesota, from 1984-2012 and followed them for all subsequent episodes through 2017. Predictors for symptomatic recurrence were identified from clinical characteristics at each stone episode. A nomogram was developed from a multivariable cox proportional hazards model using robust standard errors.

Results

There were 3,364 validated first-time kidney stone formers with 4,951 stone episodes. The stone recurrence rates per 100 person-years were 3 after the first stone episode, 7 after the second episode, 12 after the third episode, and 18 after the fourth episode or higher. A parsimonious model included the following risk factors for recurrence: younger age per 10 years (HR=0.88, p<0.001), male sex (HR=1.25, p=0.002), higher body mass index per 5 kg/m2 (HR=1.07, p=0.004), family history of stones (HR=1.36, p<0.001), pregnancy during last episode (HR=1.82, p=0.005), asymptomatic stone prior to the first validated episode (HR=1.35, p=0.008), suspected stone episode prior to the first validated episode (HR=1.75, p<0.001), brushite, struvite or uric acid stone ever (HR=1.24, p=0.16), no known calcium oxalate monohydrate stone ever (HR=0.89, p=0.08), pelvic or lower pole stone (HR=1.39, p<0.001), no ureterovesicular junction stone on imaging (HR=0.84, p=0.01), number of kidney stones on imaging (0 ref.; 1 HR=1.30, p<0.001; 2+ HR=2.03, p<0.001), and diameter of largest kidney stone on imaging (<3 mm or none ref.; 3-6 mm HR=1.25, p=0.021, >6 mm HR=0.96, p=0.79). The risk of recurrence also increases with number of past episodes (p<0.001).The final model had a C-index of 0.653; with bootstrapping, the C-index corrected for optimism was 0.643.

Conclusion

The ROKS II nomogram was developed to aid physicians in identifying patients at high versus low risk for symptomatic stone recurrence and is more generalizable than the current ROKS nomogram. With an estimate of the risk of recurrence, physicians and patients can make informed decisions on dietary and medical interventions.

Funding

  • NIDDK Support