Interoperability of phenome-wide multimorbidity patterns: a comparative study of two large-scale EHR systems.

Background: Electronic health records (EHR) are increasingly used for studying multimorbidities. However, concerns about accuracy, completeness, and EHRs being primarily designed for billing and administration raise questions about the consistency and reproducibility of EHR-based multimorbidity research. Methods: Utilizing phecodes to represent the disease phenome, we analyzed pairwise comorbidity strengths using a dual logistic regression approach and constructed multimorbidity as an undirected weighted graph. We assessed the consistency of the multimorbidity networks within and between two major EHR systems at local (nodes and edges), meso (neighboring patterns), and global (network statistics) scales. We present case studies to identify disease clusters and uncover clinically interpretable disease relationships. We provide an interactive web tool and a knowledge base combing data from multiple sources for online multimorbidity analysis. Findings: Analyzing data from 500,000 patients across Vanderbilt University Medical Center and Mass General Brigham health systems, we observed a strong correlation in disease frequencies ( Kendall's τ = 0.643) and comorbidity strengths (Pearson ρ = 0.79). Consistent network statistics across EHRs suggest a similar structure of multimorbidity networks at various scales. Comorbidity strengths and similarities of multimorbidity connection patterns align with the disease genetic correlations. Graph-theoretic analyses revealed a consistent core-periphery structure, implying efficient network clustering through threshold graph construction. Using hydronephrosis as a case study, we demonstrated the network's ability to uncover clinically relevant disease relationships and provide novel insights. Interpretation: Our findings demonstrate the robustness of large-scale EHR data for studying complex disease interactions. The alignment of multimorbidity patterns with genetic data suggests the potential utility for uncovering shared etiology of diseases. The consistent core-periphery network structure offers a strategic approach to analyze disease clusters. This work also sets the stage for advanced disease modeling, with implications for precision medicine. Funding: VUMC Biostatistics Development Award, UL1 TR002243, R21DK127075, R01HL140074, P50GM115305, R01CA227481.

Real-World Effectiveness of Preventive Pharmacological Therapy in Patients With Urolithiasis: A Retrospective Cohort Study.

RATIONALE & OBJECTIVE: Data supporting the efficacy of preventive pharmacological therapy (PPT) to reduce urolithiasis recurrence are based on clinical trials with composite outcomes that incorporate imaging findings and have uncertain clinical significance. This study evaluated whether the use of PPT leads to fewer symptomatic stone events. STUDY DESIGN: Retrospective cohort study. SETTING & PARTICIPANTS: Medicare enrollees with urolithiasis who completed 24-hour urine collections that revealed hypercalciuria, hypocitraturia, low urine pH, or hyperuricosuria. EXPOSURE: PPT (thiazide diuretics for hypercalciuria, alkali for hypocitraturia or low urine pH, or uric acid lowering drugs for hyperuricosuria) categorized as (1) adherent to guideline-concordant PPT, (2) nonadherent to guideline-concordant PPT, or (3) untreated. OUTCOME: Symptomatic stone event occurrence (emergency department [ED] visit or hospitalization for urolithiasis or stone-directed surgery). ANALYTICAL APPROACH: Cox proportional hazards regression. RESULTS: Among 13,942 patients, 31.0% were prescribed PPT. Compared with no treatment, concordant/adherent PPT use was associated with a significantly lower hazard of symptomatic stone events for patients with hypercalciuria (HR, 0.736 [95% CI, 0.593-0.915]) and low urine pH (HR, 0.804 [95% CI, 0.650-0.996]) but not for patients with hypocitraturia or hyperuricosuria. These associations were largely driven by significantly lower rates of ED visits after initiating PPT among the concordant/adherent group versus untreated patients. Patients with hypercalciuria had adjusted 2-year predicted probabilities of a visit of 3.8% [95% CI, 2.5%-5.2%%] and 6.9% [95% CI, 6.0%-7.7%] for the concordant/adherent PPT and no-treatment groups, respectively. Among patients with low urine pH, these probabilities were 4.3% (95% CI, 2.9%-5.7%) and 7.3% (95% CI, 6.5%-8.0%) for the concordant/adherent PPT and no-treatment groups, respectively. LIMITATIONS: Potential bias from the possibility that patients prescribed PPT had more severe disease than untreated patients. CONCLUSIONS: Patients with urolithiasis and hypercalciuria who were adherent to treatment with thiazide diuretics as well as those with low urine pH adherent to prescribed alkali therapy had fewer symptomatic stone events than untreated patients. PLAIN-LANGUAGE SUMMARY: Despite multiple clinical trials demonstrating the efficacy of thiazide diuretics and alkali for secondary prevention of kidney stones, they are infrequently prescribed due in part to a lack of data about their effectiveness in real-world settings. We analyzed medical claims from older adults with kidney stones for whom urine chemistry data were available. We found that patients who took prescribed thiazide diuretics for elevated urine calcium levels or alkali for low urinary pH were less likely to experience symptomatic stone recurrences than untreated patients. This benefit was expressed as lower rates of emergency department visits after initiating therapy. Our findings should inform the prescription of and adherence to treatment with thiazide diuretics and alkali for the prevention of recurrent kidney stones.

Surgeon, and Institution Characteristics Associated Surgical Preferences in the Pediatric KIDney Stone Care Improvement Network.

OBJECTIVE: To reveal barriers and opportunities to implement evidence for the management of pediatric kidney stone disease, we determined surgeon and institutional factors associated with preferences for the type of surgical intervention for kidney and ureteral stones. METHODS: We conducted a cross-sectional study of urologists participating in the Pediatric KIDney Stone Care Improvement Network (PKIDS) trial. Questionnaires ascertained strengths of urologists' preferences for types of surgery as well as characteristics of participating urologists and institutions. The outcome was the strength of preferences for ureteroscopy, shockwave lithotripsy, and percutaneous nephrolithotomy for four scenarios for which two alternative procedures are recommended by the AUA guidelines: (1) 2 cm kidney stone, (2) 9 mm proximal ureteral stone, (3) 1.5 cm lower pole kidney stone, (4) 1 cm nonlower pole kidney stone. Principal component analysis was performed to identify unique clusters of factors that explain surgical preferences. RESULTS: One hundred forty-eight urologists at 29 sites completed surveys. Stated preferences were highly skewed except for the choice between ureteroscopy and percutaneous nephrolithotomy for a 1.5 cm kidney stone. Shockwave lithotripsy ownership and local practice patterns most frequently associated with the strength of surgeons' preferences for the type of surgery. Principal component analysis revealed that three clusters of stone, patient, and heterogenous characteristics explained 30% of the variance in preferences. CONCLUSION: There is wide variation in the strengths of preferences for surgical interventions supported by current guidelines that are partially explained by surgeon and institutional characteristics. These results reveal opportunities to develop strategies for guidelines that consider real-world drivers of care.

Preventive Pharmacological Therapy and Risk of Recurrent Urinary Stone Disease.

BACKGROUND: Urinary stone disease is a prevalent condition associated with a high recurrence risk. Preventive pharmacological therapy has been proposed to reduce recurrent stone episodes. However, limited evidence exists regarding its effectiveness, contributing to its underutilization by physicians. This study aimed to evaluate the association between preventive pharmacological therapy (thiazide diuretics, alkali therapy, and uric acid-lowering medications) and clinically significant urinary stone disease recurrence. METHODS: Using data from the Veterans Health Administration, adults with an index episode of urinary stone disease from 2012 through 2019 and at least one urinary abnormality (hypercalciuria, hypocitraturia, or hyperuricosuria) on 24-hour urine collection were included. The primary outcome was a composite variable representing recurrent stone events that resulted in emergency department visits, hospitalizations, or surgery for urinary stone disease. Cox proportional hazards regression was performed to estimate the association between preventive pharmacological therapy use and recurrent urinary stone disease while adjusting for relevant baseline patient characteristics. RESULTS: Among the cohort of patients with urinary abnormalities ( n =5637), treatment with preventive pharmacological therapy was associated with a significant 19% lower risk of recurrent urinary stone disease during the 12-36-month period after the initial urine collection (hazard ratio, 0.81; 95% confidence interval, 0.65 to 1.00; P = 0.0496). However, the effectiveness of preventive pharmacological therapy diminished over longer follow-up periods (12-48 and 12-60 months after the urine collection) and did not reach statistical significance. When examining specific urinary abnormalities, only alkali therapy for hypocitraturia was associated with a significant 26% lower recurrence risk within the 12-36-month timeframe (hazard ratio, 0.74; 95% confidence interval, 0.56 to 0.97; P = 0.03). CONCLUSIONS: When considering all urinary abnormalities together, this study demonstrates that the use of preventive pharmacological therapy is associated with a lower risk of clinically significant recurrent episodes of urinary stone disease in the 12-36 month timeframe after urine collection, although only the association with the use of alkali therapy for hypocitraturia was significant when individual abnormalities were examined.

Evaluation of genetic associations with clinical phenotypes of kidney stone disease.

Introduction and Objective: We sought to replicate and discover genetic associations of kidney stone disease within a large-scale electronic health record (EHR) system. Methods: We performed genome-wide association studies (GWASs) for nephrolithiasis from genotyped samples of 5,571 cases and 83,692 controls. Among the significant risk variants, we performed association analyses of stone composition and first-time 24-hour urine parameters. To assess disease severity, we investigated the associations of risk variants with age at first stone diagnosis, age at first procedure, and time from first to second procedure. Results: The main GWAS analysis identified 10 significant loci, each located on chromosome 16 within coding regions of the UMOD gene, which codes for uromodulin, a urine protein with inhibitory activity for calcium crystallization. The strongest signal was from SNP 16:20359633-C-T (odds ratio [OR] 1.17, 95% CI 1.11-1.23), with the remaining significant SNPs having similar effect sizes. In subgroup GWASs by stone composition, 19 significant loci were identified, of which two loci were located in coding regions (brushite; NXPH1 , rs79970906 and rs4725104). The UMOD SNP 16:20359633-C-T was associated with differences in 24-hour excretion of urinary calcium, uric acid, phosphorus, sulfate; and the minor allele was positively associated with calcium oxalate dihydrate stone composition (p<0.05). No associations were found between UMOD variants and disease severity. Conclusions: We replicated germline variants associated with kidney stone disease risk at UMOD and reported novel variants associated with stone composition. Genetic variants of UMOD are associated with differences in 24-hour urine parameters and stone composition, but not disease severity.

Understanding the Barriers to Preventive Pharmacological Therapy Use in Older Patients With Urinary Stone Disease.

INTRODUCTION: Despite compelling clinical trial evidence and professional society guideline recommendations, prescription rates of preventative pharmacological therapy (PPT) for urinary stone disease are low. We sought to understand how patient- and clinician-level factors contribute to the decision to prescribe PPT after an index stone event. METHODS: We identified Medicare beneficiaries with urinary stone disease who had a 24-hour urine collection processed by a central laboratory. Among the subset with a urine chemistry abnormality (ie, hypercalciuria, hypocitraturia, hyperuricosuria, or low urine pH), we determined whether PPT was prescribed within 6 months of their collection. After assigning patients to the clinicians who ordered their collection, we fit multilevel models to determine how much of the variation in PPT prescription was attributable to patient vs clinician factors. RESULTS: Of the 11,563 patients meeting inclusion criteria, 33.6% were prescribed PPT. There was nearly sevenfold variation between the treating clinician with the lowest prescription rate (11%) and the one with the highest (75%). Nineteen percent of this variation was attributable to clinician factors. After accounting for measured patient differences and clinician volume, patients had twice the odds of being prescribed PPT if they were treated by a nephrologist (odds ratio [OR], 2.15; 95% CI, 1.79-2.57) or a primary care physician (OR, 1.78; 95% CI, 1.22-2.58) compared to being treated by a urologist. CONCLUSIONS: These findings suggest that the type of clinician whom a patient sees for his stone care determines, to a large extent, whether PPT will be prescribed.

Factors Affecting Holmium Laser Efficiency: Comparison of Laryngeal Mask Airway and Endotracheal Intubation During Ureteroscopy for Renal Stones.

Introduction: Holmium laser lithotripsy is a standard energy source used for treatment of kidney stones during flexible ureteroscopy. Efficiency of laser surgery may be affected by patient and operator characteristics or perioperative management. Here, we sought to examine intraoperative data from patients undergoing high frequency dusting with high-powered holmium laser lithotripsy to evaluate surgical and demographic factors associated with lasing efficiency (LE). Methods: A total of 82 intraoperative reports were analyzed from an ongoing laser lithotripsy clinical trial evaluating the Lumenis Pulse™ 120H holmium laser with renal stones up to 20 mm in diameter with and without Moses 2.0 technology. For each case, the total pause time between lasing activations was corrected to remove lengthy pauses and divided by the total lasing time to calculate an efficiency percentage. This was then compared with patient demographics, anesthesia administration, stone burden, postoperative complications, and stone-free rates using both univariate and multivariate analyses. Results: Of the 82 included patients, 36 received endotracheal tube (ETT) intubation and 46 had a laryngeal mask airway (LMA). Patients with ETT had significantly higher LE (78.7%) compared to those with an LMA (73.3%) in our univariate analysis (p < 0.01) as well as in the multivariate model that adjusted for maximum stone size, number of stones, stone density, and patient body mass index (p < 0.05). There was also significantly higher mean LE in patients with no postoperative complications (76.3%) compared to those with any grade (I-V) Clavien-Dindo complication within 30 days after surgery (70.0%) (p < 0.05). Conclusions: Flexible ureteroscopy and laser lithotripsy cases with higher LE are associated with lower rates of postoperative complications. The data also support the use of ETT over LMA to improve overall LE; however, this remains one consideration among many for choosing anesthesia administration. Clinical Trial Registration number: NCT04505956.

Comparison of Class-Specific Side Effects Across Preventative Pharmacologic Therapies for Kidney Stone Disease.

INTRODUCTION: Clinical guidelines recommend monitoring for metabolic derangements while on preventive pharmacologic therapy for kidney stone disease. The study objective was to compare the frequency of side effects among patients receiving alkali citrate, thiazides, and allopurinol. METHODS: Using claims data from working-age adults with kidney stone disease (2008-2019), we identified those with a new prescription for alkali citrate, thiazide, or allopurinol within 12 months after their index stone-related diagnosis or procedure. We fit multivariable logistic regression models, adjusting for cohort characteristics like comorbid illness and medication adherence, to estimate 2-year measured frequencies of claims-based outcomes of acute kidney injury, falls/hip fracture, gastritis, abnormal liver function tests/hepatitis, hypercalcemia, hyperglycemia/diabetes, hyperkalemia, hypokalemia, hyponatremia, and hypotension. RESULTS: Our cohort consisted of 1776 (34%), 2767 (53%), and 677 (13%) patients prescribed alkali citrate, thiazides, or allopurinol, respectively. Comparing unadjusted rates of incident diagnoses, thiazides compared to alkali citrate and allopurinol were associated with the highest rates of hypercalcemia (2.3% vs 1.5% and 1.0%, respectively, P = .04), hypokalemia (6% vs 3% and 2%, respectively, P < .01), and hyperglycemia/diabetes (17% vs 11% and 16%, respectively, P < .01). No other differences with the other outcomes were significant. In adjusted analyses, compared to alkali citrate, thiazides were associated with a higher odds of hypokalemia (OR=2.01, 95% CI 1.44-2.81) and hyperglycemia/diabetes (OR=1.52, 95% CI 1.26-1.83), while allopurinol was associated with a higher odds of hyperglycemia/diabetes (OR=1.34, 95% CI 1.02-1.75). CONCLUSIONS: These data provide evidence to support clinical guidelines that recommend periodic serum testing to assess for adverse effects from preventive pharmacologic therapy.

Prospective Multicenter Evaluation of Pain Before and After Removal of Nonobstructing Renal Calculi: A CoRE Initiative.

PURPOSE: Flank pain associated with stone disease is typically caused by a stone that obstructs urine flow. However, it is plausible that nonobstructing kidney stones may still cause pain. We performed a multicenter, observational trial to evaluate whether treatment of small nonobstructing calyceal stones improves pain and kidney stone-specific health-related quality of life. MATERIALS AND METHODS: Patients aged 18 years or older with nonobstructing renal stone(s) up to 10 mm in longest diameter and moderate to severe pain were recruited. All participants completed 3 questionnaires: the Brief Pain Inventory (BPI), the Patient-Reported Outcomes Measurement Information System pain interference form 6a, and the Wisconsin Stone Quality of Life questionnaire. Thereafter, all participants underwent ureteroscopy for renal stone treatment. All 3 questionnaires were repeated at 2, 6 to 8, and at 12 weeks postprocedure. The primary outcomes were change in preoperative to 12-week postoperative mean BPI score and worst BPI pain score. RESULTS: A total of 43 patients with nonobstructing kidney stones and associated flank pain were recruited. All stones were removed. Preoperatively, BPI scores for mean pain and worst pain were 5.5 and 7.2, respectively which decreased to 1.8 and 2.8 respectively at 12 weeks postoperatively. Wisconsin Stone Quality of Life questionnaire mean score increased from 70.4 to 115.3 at 12 weeks postoperatively. A total of 86% and 69% of patients had at least a 20% and 50% reduction in their mean pain scores, respectively. CONCLUSIONS: This study determined that patients benefit significantly from the removal of calyceal nonobstructing kidney stones for at least 12 weeks with a reduction in pain and an increase in quality of life. Therefore, surgical removal of these stones in this patient population should be offered as a treatment option.

Mendelian Randomization Analysis of Genetic Proxies of Thiazide Diuretics and the Reduction of Kidney Stone Risk.

Importance: Clinical trial data have called into question the efficacy of thiazide diuretics for the prevention of kidney stones. Objective: To identify whether there is an association between genetic proxies of thiazide diuretics and the risk of kidney stones. Design, Setting, and Participants: This genetic association study undertook a mendelian randomization analysis of derived exposures and outcomes from genome-wide association study summary statistics. Genetic proxies of thiazide diuretics were derived from the International Consortium for Blood Pressure. Kidney stone cases and controls were derived from the Million Veteran Program, UK Biobank, and the FinnGen study. These cross-sectional designs do not report a duration of follow-up. Data analysis was performed in May 2023. Exposure: Genetic proxies of thiazide diuretics were genetic variants in the thiazide-sensitive sodium chloride cotransporter gene associated with systolic blood pressure. Genetic proxies of ß-blockers and systolic blood pressure served as negative controls. Main Outcomes and Measures: The main outcome was the odds of kidney stones. The secondary outcomes were serum laboratory values relevant to the treatment of kidney stones. Results: The main analysis included up to 1 079 657 individuals, including 50 832 kidney stone cases and 1 028 825 controls. In a meta-analysis of all cohorts, genetic proxies of thiazide diuretics were associated with a lower odds of kidney stones (OR, 0.85; 95% CI, 0.81-0.89; P < .001). Genetic proxies of ß-blockers (OR, 1.02; 95% CI, 0.96-1.07; P = .52) and systolic blood pressure (OR, 1.00; 95% CI, 1.00-1.01; P = .49) were not associated with kidney stones. Genetic proxies of thiazide diuretics were associated with higher serum calcium (ß [SE], 0.051 [0.0092]; P < .001) and total cholesterol (ß [SE], 0.065 [0.015]; P < .001), but lower serum potassium (ß [SE], -0.073 [0.022]; P < .001). Conclusions and Relevance: In this genetic association study, genetic proxies of thiazide diuretics were associated with reduced kidney stone risk. This finding reflects a drug effect over the course of a lifetime, unconstrained by the limited follow-up period of clinical trials.

PheMIME: An Interactive Web App and Knowledge Base for Phenome-Wide, Multi-Institutional Multimorbidity Analysis.

Motivation: Multimorbidity, characterized by the simultaneous occurrence of multiple diseases in an individual, is an increasing global health concern, posing substantial challenges to healthcare systems. Comprehensive understanding of disease-disease interactions and intrinsic mechanisms behind multimorbidity can offer opportunities for innovative prevention strategies, targeted interventions, and personalized treatments. Yet, there exist limited tools and datasets that characterize multimorbidity patterns across different populations. To bridge this gap, we used large-scale electronic health record (EHR) systems to develop the Phenome-wide Multi-Institutional Multimorbidity Explorer (PheMIME), which facilitates research in exploring and comparing multimorbidity patterns among multiple institutions, potentially leading to the discovery of novel and robust disease associations and patterns that are interoperable across different systems and organizations. Results: PheMIME integrates summary statistics from phenome-wide analyses of disease multimorbidities. These are currently derived from three major institutions: Vanderbilt University Medical Center, Mass General Brigham, and the UK Biobank. PheMIME offers interactive exploration of multimorbidity through multi-faceted visualization. Incorporating an enhanced version of associationSubgraphs, PheMIME enables dynamic analysis and inference of disease clusters, promoting the discovery of multimorbidity patterns. Once a disease of interest is selected, the tool generates interactive visualizations and tables that users can delve into multimorbidities or multimorbidity networks within a single system or compare across multiple systems. The utility of PheMIME is demonstrated through a case study on schizophrenia. Availability and implementation: The PheMIME knowledge base and web application are accessible at https://prod.tbilab.org/PheMIME/. A comprehensive tutorial, including a use-case example, is available at https://prod.tbilab.org/PheMIME_supplementary_materials/. Furthermore, the source code for PheMIME can be freely downloaded from https://github.com/tbilab/PheMIME. Data availability statement: The data underlying this article are available in the article and in its online web application or supplementary material.

Quick Sequential Organ Failure Assessment Score Is a Better Predictor of Septic Shock After Percutaneous Nephrolithotomy: A Secondary Analysis of Two Multicenter Prospective Trials.

Introduction: Recent retrospective literature suggests that the quick sequential organ failure assessment (qSOFA) scoring tool is a potentially superior tool over use of the systemic inflammatory response syndrome (SIRS) criteria to predict septic shock after percutaneous nephrolithotomy (PCNL) surgery. Here we examine use of qSOFA and SIRS to predict septic shock within data series collected prospectively on PCNL patients as part of a greater study of infectious complications. Materials and Methods: We performed a secondary analysis of two prospective multicenter studies including PCNL patients across nine institutions. Clinical signs informing SIRS and qSOFA scores were collected no later than postoperative day 1. The primary outcome was sensitivity and specificity of SIRS and qSOFA (high-risk score of greater-or-equal to two points) in predicting admission to the intensive care unit (ICU) for vasopressor support. Results: A total of 218 cases at 9 institutions were analyzed. One patient required vasopressor support in the ICU. The sensitivity/specificity was 100%/72.4% (McNemar's test p < 0.001) for SIRS and was 100%/90.8% (McNemar's test p < 0.001) for qSOFA. Conclusion: Although positive predictive value for both qSOFA and SIRS in prediction of post-PCNL septic shock is low, prospectively collected data demonstrate use of qSOFA may offer greater specificity than SIRS criteria when predicting post-PCNL septic shock.

Associations Between Provider Specialty and Use of Follow-up Testing Among Patients on Preventive Pharmacological Therapy for Urinary Stone Disease.

INTRODUCTION: The AUA Medical Management of Kidney Stones guideline outlines recommendations on follow-up testing for patients prescribed preventive pharmacological therapy. We evaluated adherence to these recommendations by provider specialty. METHODS: Using claims data from working-age adults with urinary stone disease (2008-2019), we identified patients prescribed a preventive pharmacological therapy agent (a thiazide diuretic, alkali citrate therapy, allopurinol, or a combination thereof) and the specialty of the prescribing physician (urology, nephrology, and general practice). Next, we identified patients who completed a 24-hour urine collection prior to their prescription fill. We then measured adherence to 3 recommendations outlined in the AUA guideline. Finally, we fit multivariable logistic regression models evaluating associations between prescribing provider specialty and adherence to recommended follow-up testing. RESULTS: Among 2,600 patients meeting study criteria, 1,523 (59%) adhered to ≥1 follow-up testing recommendation, with a significant increase over the study period. Nephrologists had higher odds of adherence to ≥1 follow-up test compared to urologists (odds ratio, 1.52; 95% confidence interval, 1.19-1.94; P < .01). Significant differences in adherence to the 3 individual guideline recommendations were also observed by specialty. CONCLUSIONS: Following initiation of preventive pharmacological therapy, adherence to guideline-recommended follow-up testing was low overall. There exist meaningful specialty-specific differences in the use of this testing.

Feasibility of stone recurrence risk stratification using the recurrence of kidney stone (ROKS) nomogram.

This study seeks to evaluate the recurrence of kidney stones (ROKS) nomogram for risk stratification of recurrence in a retrospective study. To do this, we analyzed the performance of the 2018 ROKS nomogram in a case-control study of 200 patients (100 with and 100 without subsequent recurrence). All patients underwent kidney stone surgery between 2013 and 2015 and had at least 5 years of follow-up. We evaluated ROKS performance for prediction of recurrence at 2- and 5-year via area under the receiver operating curve (ROC-AUC). Specifically, we assessed the nomogram's potential for stratifying patients based on low or high risk of recurrence at: a) an optimized cutoff threshold (i.e., optimized for both sensitivity and specificity), and b) a sensitive cutoff threshold (i.e., high sensitivity (0.80) and low specificity). We found fair performance of the nomogram for recurrence prediction at 2 and 5 years (ROC-AUC of 0.67 and 0.63, respectively). At the optimized cutoff threshold, recurrence rates for the low and high-risk groups were 20 and 45% at 2 years, and 50 and 70% at 5 years, respectively. At the sensitive cutoff threshold, the corresponding recurrence rates for the low and high-risk groups were of 16 and 38% at 2 years, and 42 and 66% at 5 years, respectively. Kaplan-Meier analysis revealed a recurrence-free advantage between the groups for both cutoff thresholds (p < 0.01, Fig. 2). Therefore, we believe that the ROKS nomogram could facilitate risk stratification for stone recurrence and adherence to risk-based surveillance protocols.

Potential for Urolithiasis-related Research Using the Novel Medicare-Litholink Database.

INTRODUCTION: To overcome the data availability hurdle of observational studies on urolithiasis, we linked claims data with 24-hour urine results from a large cohort of adults with urolithiasis. This database contains the sample size, clinical granularity, and long-term follow-up needed to study urolithiasis on a broad level. METHODS: We identified adults enrolled in Medicare with urolithiasis who had a 24-hour urine collection processed by Litholink (2011 to 2016). We created a linkage of their collections results and paid Medicare claims. We characterized them across a variety of sociodemographic and clinical factors. We measured frequencies of prescription fills for medications used to prevent stone recurrence, as well as frequencies of symptomatic stone events, among these patients. RESULTS: In total, there were 11,460 patients who performed 18,922 urine collections in the Medicare-Litholink cohort. The majority were male (57%), White (93.2%), and lived in a metropolitan county (51.5%). Results from their initial urine collections revealed abnormal pH to be the most common abnormality (77.2%), followed by low volume (63.8%), hypocitraturia (45.6%), hyperoxaluria (31.1%), hypercalciuria (28.4%), and hyperuricosuria (11.8%). Seventeen percent had prescription fills for alkali monotherapy, and 7.6% had prescription fills for thiazide diuretic monotherapy. Symptomatic stone events occurred in 23.1% at 2 years of follow-up. CONCLUSIONS: We successfully linked Medicare claims with results from 24-hour urine collections performed by adults that were processed by Litholink. The resulting database is a unique resource for future studies on the clinical effectiveness of stone prevention strategies and urolithiasis more broadly.

Association between obstructive sleep apnea and 24-h urine chemistry risk factors for urinary stone disease.

The effect of obstructive sleep apnea (OSA) on 24-h urine parameters and resultant kidney stone risk is unknown. We sought to compare urinary lithogenic risk factors among patients with kidney stone disease with and without OSA. We performed a retrospective cohort study of adult patients with nephrolithiasis undergoing both polysomnography and 24-h urine analysis. Measures of acid load including gastrointestinal alkali absorption, urinary titratable acid, and net acid excretion were calculated from 24-h urine. We performed univariable comparisons of 24-h urine parameters between those with and without OSA and fit a multivariable linear regression model adjusting for age, sex, and BMI. Overall, there were 127 patients who underwent both polysomnography and a 24-h urine analysis from 2006 to 2018. There were 109 (86%) patients with OSA and 18 (14%) without. Patients with OSA were more commonly male, had greater BMI and had higher rates of hypertension. Patients with OSA had significantly higher levels of 24-h urinary oxalate, uric acid, sodium, potassium, phosphorous, chloride, and sulfate; higher supersaturation of uric acid; higher titratable acid, and net acid excretion; and lower urinary pH and supersaturation of calcium phosphate (p < 0.05). The difference in urinary pH and titratable acid, but not net acid excretion, remained significant when adjusting for BMI, age, and gender (both p = 0.02). OSA is associated with changes in urinary analytes that promote kidney stone formation, similar to those observed with obesity. After accounting for BMI, OSA is independently associated with lower urine pH and increased urinary titratable acid.