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Authors’ Reply

Wang, Virginia1,2,3; Coffman, Cynthia J.1,4; O’Hare, Ann M.5,6; Maciejewski, Matthew L.1,2,3

Author Information

1Health Services Research and Development, Durham Veterans Affairs Health Care System, Durham, North Carolina;

2Department of Population Health Sciences,

3Division of General Internal Medicine, Department of Medicine, and

4Department of Biostatistics and Bioinformatics, Duke University School of Medicine, Durham, North Carolina;

5Center for Health Services Research in Older Adults, Puget Sound Health Care System, Seattle, Washington; and

6Department of Medicine, University of Washington, Seattle, Washington

Correspondence: Dr. Virginia Wang, Health Services Research and Development, Durham VA Health Care System (152), 508 Fulton Street, Durham, NC 27705. Email: [email protected]

JASN 30(7):p 1338-1339, July 2019. | DOI: 10.1681/ASN.2019040402
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We appreciate Dr. Yan’s letter1 and interest in our article.2 We agree on the importance of accounting for differences in survival by race and age, especially in the dialysis population. As noted, these potential confounders are included in our adjusted models to evaluate the average effect of dialysis setting on survival (the main goal of our analysis).

Although potentially important, an analysis of survival differences across settings by race and age would address a different research question. Below we present information on sample sizes and unadjusted 2-year mortality rates after stratification by age and race (Table 1). Although there are large differences in 2-year mortality rates across some of these groups, the trends largely mirror the patterns across dialysis settings reported in our article, with no indication of potential interaction effects by age or race, which we hope ameliorates Dr. Yan’s concerns about these factors.

Table 1. - Unadjusted 2-year mortality, by dialysis setting, stratified by age and race
Selected cohort characteristics (N=27,241) Dual VA-Only VA Purchased Care Only Medicare Only
Overall mortality, unadjusted 1104 (22.8%) 269 (24.5%) 925 (30.0%) 7621 (41.8%)
Overall mortality, adjusted [95% CI] 28.9% [27.4 to 30.4] 32.4% [29.2 to 35.4] 36.0% [34.0 to 38.0] 36.7% [36.0 to 37.4]
Race/ethnicity
 White 736 (28.9%) 153 (38.0%) 660 (37.8%) 6314 (46.3%)
 Black 291 (16.3%) 93 (16.8%) 196 (19.4%) 1004 (29.1%)
 Hispanic 51 (14.3%) 16 (14.4%) 36 (17.1%) 143 (21.9%)
 Other 26 (16.4%) Not shown (size <12) 33 (29.7%) 160 (33.3%)
Age, yr
 <55 90 (12.3%) 17 (9.5%) 61 (14.4%) 179 (16.8%)
 55–64 376 (17.7%) 82 (17.4%) 330 (24.0%) 644 (25.1%)
 65–74 295 (26.3%) 71 (30.9%) 242 (35.5%) 1646 (36.2%)
 75–84 272 (37.7%) 74 (42.5%) 234 (46.5%) 3465 (48.0%)
 ≥85 71 (45.8%) 25 (54.4%) 58 (59.8%) 1687 (59.6%)
Data are shown as n (%), unless otherwise indicated. Reported n are number of deaths and % deaths among cohort members within category. VA, Department of Veterans Affairs; 95% CI, 95% confidence interval.

Because of the large number of covariates in the model and smaller sample size in the Department of Veterans Affairs only cohort, formal stratified analysis could be problematic. With larger cohorts, examining the presence and magnitude of race/ethnicity and age differences in dialysis setting comparisons of patient outcomes are an important and promising area for future research.

Disclosures

Dr. Maciejewski reports ownership of Amgen stock from his spouse’s employment. Dr. O’Hare has received funding from the VA, CDC, and NIH, as well as honoraria/speaker fees from UpToDate, Fresenius Medical Care, Dialysis Clinics Inc., the University of Alabama at Birmingham, and the Coalition for the Supportive Care of Kidney Patients. All of the remaining authors have nothing to disclose.

The authors thank Dr. David Edelman and Dr. Paul Hebert for thoughtful comments.

This study was funded by the Department of Veterans Affairs (VA) Health Services Research and Development Service (grant IIR 12-342) and a VA Research Career Scientist award (RCS 10-391), and supported by the Center of Innovation for Health Services Research (grant CIN 13-410) at the Durham VA Health Care System.

The interpretation and reporting of these data are the responsibility of the authors and do not reflect the official policy or interpretation of the US Government or the Department of Veterans Affairs.

Published online ahead of print. Publication date available at www.jasn.org.

See related Letters to the Editor, “Confounding of Race/Ethnicity and Age in the Survival among Veterans Obtaining Dialysis in VA and Non-VA Settings,” on page .

References

1. Yan G: Confounding of Race/Ethnicity and Age in the Survival among Veterans Obtaining Dialysis in VA and Non-VA Settings. J Am Soc Nephrol 30: 1337, 2019
2. Wang V, Coffman CJ, Stechuchak KM, Berkowitz TSZ, Hebert PL, Edelman D, et al.: Survival among Veterans Obtaining Dialysis in VA and Non-VA Settings. J Am Soc Nephrol 30: 159–168, 2019
    Keywords:

    dialysis survival; confounding; Veterans Health Administration; comparative analysis

    Copyright © 2019 by the American Society of Nephrology