Non-adherence to stone meds raises hospitalization risk

London-When it comes to urinary stone disease, it appears that prescribers know what they’re doing. According to a study presented at the World Congress of Endourology and SWL in London, non-adherence to kidney stone medications led to a significant increase in adverse health outcomes. 

“Adherence to preventative pharmacologic therapy agents in urinary stone disease is associated with decreased rates of emergency department (ED) visits, hospitalizations, and stone-directed surgery,” reported co-author Yooni Yi, MD, urology resident at the University of Michigan, Ann Arbor, who worked on the study with first author Casey Dauw, MD, senior author John Hollingsworth, MD, and colleagues.

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As Dr. Yi explained, urinary stone disease is best viewed as a chronic condition in which secondary prevention plays an important role. However, the effect of non-adherence to preventive pharmacologic therapy on adverse health outcomes is unknown. For this study, the goal of the authors was to evaluate the rates of stone-related ED visits, hospitalizations, and stone-directed surgery within 2 years of diagnosis between adherent and non-adherent patients with urinary stone disease.

Using MarketScan data from 2002 to 2006, the authors identified 8,890 patients with a diagnosis of nephrolithiasis who were prescribed preventive pharmacologic therapy with a 2-year follow-up. Dr. Yi and colleagues measured adherence using the proportion of days covered (PDC) formula, with adherent defined as PDC >80%.

According to Dr. Yi, only 51.1% of patients were found to be adherent to therapy.

“Adherent patients tended to be older, less healthy, and from the Midwest,” said Dr. Yi. “They also were more likely to be salaried, work part-time, and have comprehensive health insurance.”

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When compared to non-adherent patients, those who were adherent were also found to have lower odds of ED visits, stone-directed surgery, or hospital admission.

“Patients adherent to preventative pharmacologic therapy had 27% lower ED visits, 41% lower odds of hospital readmission, and 23% lower odds of stone-directed surgery. This indicates a significant impact that adherence has on health outcomes,” said Dr. Yi.

NEXT: Predicting adherence difficulty

Predicting adherence difficulty

While the authors observed common factors among adherent patients, which may influence treatment duration, Dr. Yi acknowledged the difficulty of predicting adherence in advance.

“It’s truly difficult to assess why or why not these patients were adherent,” she said, “so I think that might be the next thing that we look at. I’d like to determine whether or not patients are adherent because of the frequency of medications or side effects of medications or some other cause. In the meantime, these results at least provide a means of conversation between the physician and the patient that will hopefully incentivize them when it comes to their stone therapy in the future.”

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Despite the obvious statistical improvement in outcomes related to adherence, one member of the audience expressed surprise that the gap between adherent and non-adherent patients was not more pronounced. When questioned about the relatively small difference in the need for surgery between adherent and non-adherent groups, Dr. Yi said the difference was not unexpected.

“But one thing that you might consider is that this is only a 2-year follow-up,” she responded. “If you were to extend this study out to a 5-year follow-up, maybe there would be more of an impact.”