Beneficial Impact of Follow-Up 24-Hour Urine Testing on Adherence to Pharmacological Therapy for Kidney Stone Prevention

Purpose: Preventive pharmacological therapy (PPT) is recommended for certain patients with urinary stone disease to reduce their recurrence risk, but they frequently do not adhere. With causal inference methods, we evaluated whether follow-up urine testing could be used to improve PPT adherence. Materials and Methods: Using claims data from Optum’s deidentified Clinformatics Data Mart database (2008-2019), we identified patients with urinary stone disease who were prescribed PPT (thiazide diuretic, alkali therapy, or allopurinol) after baseline 24-hour urine testing and assessed their adherence with the proportion of days covered method. After distinguishing between patients who did and did not receive follow-up urine testing, we examined the association between follow-up testing and PPT adherence with logistic regression. We then emulated a target trial using propensity score matching, stratification, and doubly robust estimators to estimate the equivalent causal effect. Results: Among 4166 patients, 496 (11.9%) completed both baseline and follow-up testing. Follow-up testing was associated with a 9.0% increase in adherence odds after adjusting for sociodemographic, behavioral, and disease-related and treatment-related patient characteristics. Furthermore, we estimated a 7.1% increase in proportion of days covered caused by follow-up testing using causal inference methods. Subgroup analyses indicated the most significant effects are among women, those with low baseline medication adherence, and those not at high risk of stone formation. Conclusions: These data suggest that follow-up urine testing after starting PPT may have a beneficial effect on long-term medication adherence.