Abstract
Purpose:
Recent observational studies reporting a lack of benefit from 24-hour urine testing for urinary stone disease (USD) prevention assumed testing included all components recommended from clinical guidelines. We sought to assess the completeness of 24-hour urine testing in the VA population.
Materials and methods:
From the VHA Corporate Data Warehouse (2012–2019), we identified patients with USD (n=198,621) and determined those who saw a urologist and/or nephrologist, and received 24-hour urine testing within 12 months of their index USD encounter. Through Logical Observation Identifiers Names and Codes, we evaluated each collection’s completeness, defined as including all of urine volume, calcium, oxalate, citrate, uric acid, and creatinine. We then fit a multilevel logistic regression model with random effects for VHA facility to evaluate factors associated with specialist follow-up, testing, and testing completeness.
Results:
Specialist follow-up occurred in 54.3% and was stable over time. Testing occurred in 8.4%, declining from 9.3% in 2012 to 7.2% in 2019. Of tests performed, 54.6% were complete (43.7% increasing to 62.7% from 2012–2019). In adjusted analysis, there was high between-facility variation in specialist follow-up (median OR 2.0; 95% CI 1.7–2.0), testing (median OR 2.2, 95% CI 1.9–2.4), and testing completeness (median OR, 6.0, 95% CI 4.5–7.3). Individual facilities contributed 52% (intraclass correlation coefficient, 0.52; 95% CI, 0.44–0.57) towards the observed variation in testing completeness.
Conclusions:
Approximately 1 in 12 U.S. Veterans with USD receive metabolic testing and half of these tests are complete. Addressing facility level variation in testing completeness may improve USD care.
Keywords: kidney, urolithiasis, secondary prevention, urine specimen collection
Introduction
Under contemporary practice guidelines for urinary stone disease (USD) prevention, 24-hour urine testing plays an important role in the management strategy to reduce future recurrence episodes. 1–3 While it is known that clinicians at least modify and tailor pharmacologic treatment based on testing,4 several recent observational studies have reported no differences in rates of recurrent stone events between patients with and without 24-hour testing.5–7 Accordingly, the American College of Physicians does not endorse testing,8 stating the evidence is insufficient to conclude testing is beneficial.
While it is possible that clinicians may have difficulty interpreting 24-hour urine results,9 a plausible explanation is that these studies assumed patients received testing for all components of the 24-hour urine as outlined by clinical guidelines.1 The omission of one or more components has the potential to limit the utility of metabolic evaluation. Providers may not have sufficient information to act upon testing results and formulate preventative interventions. Whether providers need to order each component of the 24-hour urine test individually or as part of a panel-based order set may be influenced by facility level factors.
Within this context, we conducted an observational study of adults with USD with data from the Veterans Health Administration (VHA) to examine whether testing and testing completeness were associated with facility-level variation in the evaluation for USD prevention. Additionally, since multiple clinical guidelines were introduced between 2014 and 2016,1–3,8 this motivated an examination of a contemporary cohort to evaluate time trends for rates of specialist follow-up – known to influence the likelihood of testing,10 24-hour urine testing, and 24-hour urine testing completeness, following a recent USD diagnosis. We hypothesized that the facility where a Veteran received their care influenced the completeness of their USD evaluation.
Materials and Methods
Data source and study population
We utilized files from the VHA Corporate Data Warehouse comprising inpatient and outpatient records from 23.5 million living and deceased U.S. Veterans who primarily use the VHA for their healthcare needs. First, we identified adults within the VHA who were 18 years or older with a recent USD episode between 2012 and 2019, defined as at least one inpatient or two outpatient evaluation and management encounters within a 12 month period or one surgical encounter for USD. We implemented a one-year washout, excluding those with a USD-related encounter in 2011. The relevant USD diagnosis and procedure codes are listed in the Appendix. For patients with multiple encounters for USD, we considered the first encounter as the index USD encounter.
24-hour urine testing and testing completeness
We identified receipt of 24-hour urine testing by the first instance of 24-hour urine testing of calcium, citrate, oxalate, or uric acid among patients with USD within 12 months after the index USD encounter using Logical Observation Identifiers Names and Codes (LOINC) (listed in the Appendix). We identified additional tests for urine volume, creatinine, potassium, sodium, and pH within 30 days of the initial test for calcium, citrate, oxalate, or uric acid.
We defined a complete 24-hour urine test as including all of urine calcium, oxalate, citrate, uric acid, volume, and creatinine within 30 days of the test for calcium, citrate, oxalate, or uric acid; and we considered tests that did not meet this criterion as incomplete. When we examined other guideline-recommended 24-hour urine tests, such as pH, sodium, and potassium,1 the full completeness rates for the overall population was 1.1%. We therefore chose to define a complete 24-hour urine test using the panel of common 24-hour urine tests.
Specialist follow-up after USD diagnosis
Next, we examined for urology and/or nephrology specialist evaluation within the first 12 months after the index USD encounter using clinic stop codes and provider codes. The relevant provider or clinic stop codes are listed in the Appendix.
Statistical analysis
For our initial analytic step, we obtained descriptive statistics on patients with USD overall, among those with specialist visits, 24-hour urine testing, and complete testing across a range of sociodemographic factors, including age, sex, race, ethnicity, high risk for USD recurrence status, year of index USD encounter, and geographic region (Northeast, South, Midwest, West).
We defined high risk status as the presence of at least one concomitant comorbid condition associated with USD risk within 12 months prior to the index USD encounter (see the Appendix for list of conditions). We performed bivariate statistics to compare patient, provider, and facility level factors between patients with and without specialist visits, 24-hour urine testing, and complete testing.
We then fit multilevel logistic regression models with random effects for facility to evaluate factors associated with specialist visits, any 24-hour urine test testing (any versus none), and complete urine testing (complete versus incomplete). We calculated intraclass correlation coefficients (ICC) and median odds ratios (MOR) and corresponding 95% confidence intervals (CIs) from the multilevel models to quantify the amount of variation in the outcomes attributed to the individual VHA facility. Median odds ratios represent the median difference in odds of the outcome comparing two randomly selected facilities.11 We controlled for patient age, sex, race, ethnicity, high risk status, year of index USD encounter, and geographic region. We excluded VHA facilities with fewer than five patients with USD, and facilities with fewer than five 24-hour urine tests for the completeness analysis. For each VHA facility, model adjusted predicted probabilities of 24-hour urine testing performed, specialist follow-up or complete urine testing, along with 95% CIs, were calculated and plotted in rank order.
We conducted all analyses using R version 4.0.5 (R Foundation, Vienna, AU). We performed two-sided significance testing with alpha set at 0.05. The study was approved by the Institutional Review Board of the VA Ann Arbor Healthcare System with a waiver of informed consent. All methods were performed in accordance with relevant guidelines and regulations.
Results
There were 198,621 individuals with an index USD encounter identified with mean ± SD age 61.6 ± 14.4 years, 93.4% male, 84.9% white race, and 27.6% with at least one or more concomitant conditions associated with USD recurrence risk (see Table 1). Most USD cases were identified in the South (46.6%). The number of USD cases per year remained stable from 13.6% in 2012 to 12.5% in 2019.
Table 1.
Patient Characteristics Overall, and Those Receiving Specialist Follow-up and 24-Hour Urine Testing
| Overall (N=198621)* | Specialist Follow-up (N=107877) | 24 Hour Urine Testing (N=16702) | |
|---|---|---|---|
| Age, years | |||
| Mean (SD) | 61.6 (14.4) | 61.6 (13.7) | 59.2 (13.1) |
| Range | 18.0 – 104.0 | 19.0 – 104.0 | 19.0 – 94.0 |
| Age Quantiles, years | |||
| 18 – 52 | 47106 (23.7%) | 24318 (51.6%) | 4528 (9.6%) |
| 53 – 63 | 46280 (23.3%) | 26484 (57.2%) | 4430 (9.6%) |
| 64 – 70 | 54570 (27.5%) | 31244 (57.3%) | 4946 (9.1%) |
| 71 – 104 | 50665 (25.5%) | 25831 (51.0%) | 2798 (5.5%) |
| Sex | |||
| Female | 13199 (6.6%) | 7222 (54.7%) | 1517 (11.5%) |
| Male | 185422 (93.4%) | 100655 (54.3%) | 15185 (8.2%) |
| Race | |||
| American Indian or Alaskan Native | 1606 (0.9%) | 797 (49.6%) | 151 (9.4%) |
| Asian | 1530 (0.8%) | 892 (58.3%) | 229 (15.0%) |
| Black or African American | 23185 (12.4%) | 13465 (58.1%) | 1685 (7.3%) |
| Native Hawaiian or Other Pacific Islander | 1922 (1.0%) | 976 (50.8%) | 165 (8.6%) |
| White | 158995 (84.9%) | 85875 (54.0%) | 13519 (8.5%) |
| Ethnicity | |||
| Hispanic or Latino | 12788 (6.7%) | 7081 (55.4%) | 1119 (8.8%) |
| Not Hispanic or Latino | 179189 (93.3%) | 97314 (54.3%) | 15017 (8.4%) |
| High Risk Status of Kidney Stones | |||
| High Risk | 54873 (27.6%) | 29681 (54.1%) | 4768 (8.7%) |
| Not High Risk | 143748 (72.3) | 78196 (54.4%) | 11934 (8.3%) |
| Incident Event Year | |||
| 2012 | 26916 (13.6%) | 14130 (52.5%) | 2512 (9.3%) |
| 2013 | 24044 (12.1%) | 13056 (54.3%) | 2203 (9.2%) |
| 2014 | 24003 (12.1%) | 13056 (54.4%) | 2031 (8.5%) |
| 2015 | 23403 (11.8%) | 13504 (57.7%) | 2178 (9.3%) |
| 2016 | 23983 (12.1%) | 13358 (55.7%) | 2094 (8.7%) |
| 2017 | 24863 (12.5%) | 13718 (55.2%) | 1926 (7.7%) |
| 2018 | 26572 (13.4%) | 13722 (51.6%) | 1975 (7.4%) |
| 2019 | 24837 (12.5%) | 13333 (53.7%) | 1783 (7.2%) |
| Region | |||
| Midwest | 40858 (20.6%) | 22335 (54.7%) | 3613 (8.8%) |
| Northeast | 24563 (12.4%) | 13475 (54.9%) | 1676 (6.8%) |
| South | 92461 (46.6%) | 49433 (53.5%) | 6404 (6.9%) |
| West | 40739 (20.5%) | 22634 (55.6%) | 5009 (12.3%) |
For the three columns, the left column showing the Overall cohort contains column percents, and the middle and right columns display row percents
SD: standard deviation; VHA: Veteran’s Health Administration
Specialist follow-up with a urologist and/or nephrologist occurred in 54.3% overall (nephrology only 4.8%, urology only 90.0%, nephrology and urology 5.2%) within the first year after USD diagnosis and remained stable from 2012 to 2019 (see Table 1). There were notable differences in rates of specialist follow-up by race with highest rates observed in Asian (58.3%) and Black patients (58.1%). In the multilevel logistic regression model, there were differences in specialist follow-up by race, ethnicity, the presence of high-risk concomitant conditions, and year of diagnosis (Table 2). Large between-facility variation in specialist follow-up was observed (MOR, 1.97; 95% CI, 1.72 to 2.03), and individual facilities contributed 13% to the observed variation in specialist follow-up (ICC, 0.13; 95% CI, 0.09 to 0.14). The model adjusted predicted probability of specialist follow-up for each VHA facility is shown in Figure 1a with range of 5% to 74% and a median 57% follow-up rate.
Table 2.
Mixed Effect Models with Random Intercept for VHA Facility for Specialist Follow-up and 24-Hour Urine Testing
| Specialist Follow-up | 24-Hour Urine Testing | |||
|---|---|---|---|---|
| Odds Ratio | 95% CI | Odds Ratio | 95% CI | |
| VHA Facility Median Odds Ratio | 1.97 | 1.72 – 2.03 | 2.15 | 1.94 – 2.36 |
| VHA Facility Intra-Class Correlation | 0.13 | 0.09 – 0.14 | 0.17 | 0.13 – 0.19 |
| Age, Scale by Decades | 1.00 | 0.99 – 1.00 | 0.89 | 0.88 – 0.90 |
| Sex | ||||
| Male (Reference: Female) | 0.99 | 0.95 – 1.03 | 0.78 | 0.73 – 0.83 |
| Race | ||||
| American Indian or Alaska Native (Reference: White) | 0.86 | 0.77 – 0.95 | 0.96 | 0.80 – 1.14 |
| Asian | 1.32 | 1.18 – 1.48 | 1.39 | 1.20 – 1.62 |
| Black | 1.18 | 1.15 – 1.22 | 0.90 | 0.84 – 0.95 |
| Native Hawaiian or Other Pacific Islander | 1.06 | 0.96 – 1.17 | 0.96 | 0.81 – 1.14 |
| Ethnicity | ||||
| Hispanic or Latino (Ref: Not Hispanic or Latino) | 1.09 | 1.04 – 1.15 | 0.97 | 0.90 – 1.05 |
| Risk of Kidney Stones | ||||
| High Risk (Reference: Not High Risk) | 0.96 | 0.94 – 0.98 | 1.09 | 1.04 – 1.13 |
| Incident Event Year | ||||
| 2013 (Reference: 2012) | 1.08 | 1.04 – 1.12 | 0.97 | 0.91 – 1.03 |
| 2014 | 1.07 | 1.03 – 1.11 | 0.88 | 0.82 – 0.94 |
| 2015 | 1.23 | 1.19 – 1.28 | 0.96 | 0.90 – 1.02 |
| 2016 | 1.13 | 1.08 – 1.17 | 0.91 | 0.85 – 0.97 |
| 2017 | 1.09 | 1.05 – 1.13 | 0.8 | 0.75 – 0.85 |
| 2018 | 0.96 | 0.93 – 1.00 | 0.77 | 0.72 – 0.82 |
| 2019 | 1.02 | 0.98 – 1.06 | 0.73 | 0.69 – 0.78 |
| Region | ||||
| Northeast (Reference: Midwest) | 0.97 | 0.65 – 1.45 | 0.74 | 0.47 – 1.18 |
| South | 0.90 | 0.64 – 1.25 | 0.72 | 0.49 – 1.06 |
| West | 0.83 | 0.57 – 1.21 | 1.18 | 0.77 – 1.81 |
CI: confidence interval; VHA: Veteran’s Health Administration
Figure 1a.
Caterpillar Plot of Model Adjusted Predicted Probability of Specialist Follow-up by VHA Facility
VHA: Veteran’s Health Administration; Median predicted probability: 0.57
Overall rates of 24-hour urine testing occurred in 8.4% within the first year after the index USD encounter (see Table 1). Rates of testing declined from 9.3% in 2012 to 7.2% in 2019. Those receiving tests were younger (mean age 59.2 years), and proportionally more female than male (11.5% of females vs 8.2% of males). Asians most commonly received testing (15.0%), and regional differences in rates of testing were observed. Receipt of 24-hour urine testing was associated with sex, race, the presence of high-risk concomitant conditions, and year of testing (see Table 2). Between-facility variation in testing was observed (MOR, 2.15, 95% CI, 1.94 to 2.36), and individual facilities contributed 17% to the observed variation in 24-hour urine testing (ICC, 0.17; 95% CI 0.13 to 0.19). The model adjusted predicted probability of 24-hour urine testing for each VHA facility is shown in Figure 1b with range of 3% to 67% and with a median 20% testing rate.
Figure 1b.
Caterpillar Plot of Model Adjusted Predicted Probability of 24-Hour Urine Testing by VHA Facility
VHA: Veteran’s Health Administration; Median predicted probability: 0.20
Individuals meeting completeness criteria was observed in 54.6% of those receiving 24-hour urine testing (see Table 3). Rates of testing completeness increased from 43.7% in 2012 to 62.7% in 2019. Those with complete urine testing were more often male (55.0% compared to 51.7% of females) and without high-risk concomitant conditions. Asians had the highest percentage of complete testing at 75.1%. Hispanics had higher levels of complete testing compared to non-Hispanics. Testing completeness was most commonly observed in the West. Unadjusted rates of 24-urine completeness among VHA facilities ranged from as low as 0% to as high as 98%. In the multilevel logistic regression model shown in Table 3, there were adjusted differences in testing completeness between age, sex, ethnicity, presence of high-risk concomitant conditions, year of diagnosis, and region. In the adjusted analysis, there was high between-facility variation in 24-hour urine completeness (MOR, 5.96; 95% CI, 4.53 to 7.34). Collectively, individual facilities contributed 52% (ICC, 0.52; 95% CI, 0.44 to 0.57) to the observed variation in 24-hour urine completeness. The model adjusted predicted probability of complete testing for each VHA facility is shown in Figure 2 with a range of 0% to 96% and a median 21% testing rate.
Table 3.
Patient Characteristics for Those Receiving Complete 24-Hour Urine Testing and Mixed Effect Models with Random Intercept for VHA Facility
| Complete 24 Hour Urine Testing (N=9130) * | Complete 24-Hour Testing | ||
|---|---|---|---|
| Odds sRatio | 95% CI | ||
| VHA Facility Median Odds Ratio | 5.96 | 4.53 – 7.34 | |
| VHA Facility Intra-Class Correlation | 0.52 | 0.44 – 0.57 | |
| Age, Scaled by decades | 0.95 | 0.92 – 0.98 | |
| Age, years | |||
| Mean (SD) | 58.9 (13.2) | ||
| Range | 19 – 94 | ||
| Age Categories, years | |||
| 18 – 52 | 2558 (56.5%) | ||
| 53 – 63 | 2367 (53.4%) | ||
| 64 – 70 | 2695 (54.5%) | ||
| 71 – 104 | 1510 (54.0%) | ||
| Sex | |||
| Female | 784 (51.7%) | Reference | |
| Male | 8346 (55.0%) | 1.24 | 1.07 – 1.45 |
| Race | |||
| American Indian or Alaska Native | 96 (63.6%) | 0.96 | 0.62 – 1.49 |
| Asian | 172 (75.1%) | 1.05 | 0.71 – 1.56 |
| Black or African American | 840 (49.9%) | 0.93 | 0.81 – 1.07 |
| Native Hawaiian or Other Pacific Islander | 102 (61.8%) | 0.84 | 0.54 – 1.30 |
| White | 7332 (54.2%) | Reference | |
| Ethnicity | |||
| Hispanic or Latino | 649 (58.0%) | 1.28 | 1.05 – 1.57 |
| Not Hispanic or Latino | 8121 (54.1%) | Reference | |
| Risk of Kidney Stones | |||
| High Risk | 2409 (50.5%) | 0.8 | 0.73 – 0.88 |
| Not High Risk | 6721 (56.3%) | Reference | |
| Incident Event Year | |||
| 2012 | 1098 (43.7%) | Reference | |
| 2013 | 1008 (45.8%) | 1.07 | 0.92 – 1.25 |
| 2014 | 1013 (49.9%) | 1.48 | 1.26 – 1.74 |
| 2015 | 1215 (55.8%) | 2.03 | 1.73 – 2.39 |
| 2016 | 1233 (58.9%) | 2.66 | 2.25 – 3.14 |
| 2017 | 1205 (62.6%) | 3.56 | 3.00 – 4.22 |
| 2018 | 1240 (62.8%) | 3.41 | 2.88 – 4.03 |
| 2019 | 1118 (62.7%) | 3.36 | 2.82 – 4.00 |
| Region | |||
| Midwest | 1401 (38.8%) | Reference | |
| Northeast | 849 (50.7%) | 1.96 | 0.65 – 5.89 |
| South | 2898 (45.3%) | 1.03 | 0.42 – 2.54 |
| West | 3982 (79.5%) | 8.07 | 2.93 – 22.26 |
The proportions are calculated using the respective counts from those receiving any 24-hour urine collections as the denominator (as displayed in the right-most column in Table 1).
CI: confidence interval; SD: standard deviation; VHA: Veteran’s Health Administration
Figure 2.
Caterpillar Plot of Model Adjusted Predicted Probability of Complete 24-Hour Urine Testing by VHA Facility
VHA: Veteran’s Health Administration; Median predicted probability 0.21
Discussion
In this study of U.S. Veterans who use the VHA for their USD, we identified several important key findings. First, specialist follow-up with a nephrologist and/or urologist within the first year after initial diagnosis was observed in over half of patients, which was relatively stable over the study period. Second, metabolic 24-hour urine testing rates occurred in approximately 1 in 12 of individuals, and this figure is similar to the testing rate previously reported for those with employer-based insurance.12 Rates of testing within the VHA had a declined two percentage points over the study interval, despite the introduction of clinical guidelines during it.1–3,8 Third, among those receiving 24-hour urine testing, approximately half had complete testing, and this figure increased from approximately 40% in 2012 to 60% in 2019. Finally, we observed that facility level variation significantly contributes to the observed variation independent of patient characteristics. In other words, where Veterans with USD receive their care strongly influences whether 24-hour urine testing is performed and whether testing includes a full panel of urinary analytes.
While other studies have reported specialist care among privately insured patients with USD,12,13 this is the first study to examine completeness of 24-hour urine parameters among patients with USD. Within the VHA population, Song et al. examined patients with USD from 2007 to 2013 and reported rates of 24-hr urine abnormalities, medication use, and subsequent clinical outcomes.4,5 Our findings in this more contemporary cohort show that before and after clinical guidelines were published, there was a decline of 24-hour urine testing over time, although rates for testing completeness increased during the same period. Notably, the AUA guidelines recommend 24-hour urine testing in high-risk or interested first-time stone formers, and recurrent stone formers - not every patient with a kidney stone diagnosis.1 These observations, coupled with the observed variation for 24-hour urine testing and testing completeness, may reflect the uncertainty regarding the clinical utility of 24-hour urine testing for stone prevention.
The findings of this study are relevant for improving the quality of care for individuals with USD. High rates of incomplete 24-hour urine testing raise questions of whether this is true of non-VHA populations. Several prior published studies reporting on the limited utility of 24-hour urine testing in VHA and non-VHA have assumed that the administrative billing code for a single or a limited list of 24-hour urine components (e.g. urine oxalate) was a sufficient indicator for complete 24-hour urine testing.5–7,14 Here, we show that at least in the VHA population, providers may not have sufficient information to act upon testing results and formulate preventative interventions. In 2014, the AUA published guidelines recommending the components of 24-hour testing at minimum should include total volume, pH, calcium, oxalate, uric acid, citrate, sodium, potassium, and creatinine.1 In addition, the availability of a complete set of urinary values can allow for calculation of supersaturation for specific stone types, which has been shown to indicate risk for future stone episodes.15,16 For this analysis, when we examined a full set of values that additionally included pH, sodium, and potassium as recommended in clinical guidelines,1 the full completeness rates for the overall cohort was 1.1%. We therefore chose here to focus on a more broadly defined subset.
There are several limitations to this study. Administrative data are susceptible to omitted variable bias and misclassification bias. Due to the observational study design, we lack information on granular details that may shed more information on which provider and facility factors relate to when testing is performed and testing completeness. These data are limited to care provided within the VA, so care provided (e.g., specialist follow up or urine tests) outside of the VA would not be captured. However, we identified patients whose initial episode USD was diagnosed and/or treated within VA, so it is likely that this population is enriched with patients primarily using VA for their USD care. It is possible that we did not fully capture results from VA facilities that send urine testing to outside laboratories.14 Additionally, the decline of within-facility testing may be due to an increase in outside lab testing over time. We cannot exclude the possibility of unmeasured confounding, though the main finding of facility-level contribution to testing completeness is likely robust given the strength of association. Additionally, these data from U.S. adult Veterans may not be generalizable to other populations.
Not with standing these limitations, our study has important clinical implications. Namely, when 24-hour urine components cannot be ordered together as a panel, providers may need to order each component individually, which can be burdensome and time intensive. Not all clinical laboratories can perform the complete set of testing recommend as part of USD metabolic evaluations, and often multiple commercial 3rd party laboratories are utilized for panel-based testing. With the widespread use of electronic health records and order entry, panel-based testing can be developed at the facility level, as suggested by our observation of some facilities with very high rates of testing completion.
Conclusions
Among U.S. Veterans with USD, specialist follow-up with a urologist and/or nephrologist occurs in over half of individuals, and such referrals remained stable over time. The prevalence of metabolic 24-hour urine testing within the first year of USD diagnosis is low and declined from 2012 to 2019. Completeness of 24-hour urine testing occurs in approximately half and increased over the study period. Individual facilities contribute a substantial degree to the observed variation in specialist follow-up, 24-hour urine testing, and testing completeness. Reducing facility level variation in testing completeness may improve USD preventative care. Further studies could examine whether testing completeness is highly prevalent in non-VHA populations with USD. Finally, understanding what providers do with the information gained from testing is an area of need, as would whether increasing testing completeness leads to reduction in USD recurrence rates.
Supplementary Material
Acknowledgements
Supported by National Institutes of Health Grant 1R01DK121709-01A1. Supported in part by Department of Veterans Affairs Merit Review (I01 HX003091 to ACP and JTL).
Contributor Information
Ryan S. Hsi, Department of Urology, Vanderbilt University Medical Center, Nashville, Tennessee
Autumn N. Valicevic, Department of Internal Medicine, Veterans Administration, Veterans Affairs Medical Center, Ann Arbor, Michigan
Sanjeevkumar R. Patel, Nephrology Division of Internal Medicine, University of Michigan School of Medicine, Ann Arbor, Michigan Department of Internal Medicine, Veterans Administration, Veterans Affairs Medical Center, Ann Arbor, Michigan.
Mary K. Oerline, Dow Division of Health Services Research, Department of Urology, University of Michigan
Alan C. Pao, Division of Nephrology, Department of Medicine, Stanford University School of Medicine, Stanford, California Veterans Affairs Palo Alto Health Care System, Palo Alto, California; Department of Urology, Stanford University School of Medicine, Stanford, California.
John T. Leppert, Division of Nephrology, Department of Medicine, Stanford University School of Medicine, Stanford, California Veterans Affairs Palo Alto Health Care System, Palo Alto, California; Department of Urology, Stanford University School of Medicine, Stanford, California.
John M. Hollingsworth, Dow Division of Health Services Research, Department of Urology, University of Michigan
Vahakn Shahinian, Dow Division of Health Services Research, Department of Urology, University of Michigan; Division of Nephrology, Department of Internal Medicine, University of Michigan.
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Associated Data
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