Do You Need to Stay in School to Get a Kidney Transplant?

Kidney transplantation is the preferred form of renal replacement for many patients with end-stage renal disease (ESRD).1 Despite the demonstrated benefits of kidney transplantation over dialysis, the number of patients who receive a transplant falls short of what is needed, and a majority of patients on the wait-list remain there too long without an organ. Moreover, a substantial number of ESRD patients are neither presented with kidney transplantation as an alternative to dialysis nor evaluated for a kidney transplant. Several barriers have been identified to transplantation and to placement on the waitlist for a kidney transplant. While the root causes that influence transplant referrals vary and are often interrelated, commonly cited factors include race and ethnicity, socioeconomic status, and the practice patterns of dialysis providers2, 3; however, reports on such factors usually fail to identify the element within these broader characteristics that can explain the failed access to transplantation.

In this issue of AJKD, Schaeffner et al, expanding on prior evidence that socioeconomic status has been shown to influence transplantation rates and referral, examine the effect of educational status—one component of socioeconomic status—on access to a kidney transplant. The authors conducted a retrospective analysis of the second wave of the Dialysis Morbidity and Mortality Study (DMMS), which was comprised of incident hemodialysis and peritoneal dialysis patients enrolled in 1996 and 1997. After exclusion of a substantial portion of the cohort from analysis, 692 of the remaining 3,245 participants were wait-listed for transplant; of note, we are not told how many of the cohort received a living-donor transplant. The authors report that 670 patients from the incident cohort received a transplant over the observation period ending in 2004, but it is not clear which of these transplant recipients came from the wait-list. Approximately 34% of the DMMS Wave 2 participants had fewer than 12 years of education while 15% held a college degree. However, there were no further details on the amount of education among individuals with fewer than 12 years of education. College graduates had more than a 3 times higher likelihood of being placed on the wait-list than DMMS Wave 2 participants with fewer than 12 years of education, but, once listed, were equally likely to receive a first transplant at any time after placement on the wait-list. Not surprisingly, as a result of selection bias, education did not confer a highly significant or consistent benefit on transplant outcomes. There is no information as to how many participants in the cohort died while on the transplant waiting list.

The conclusions of the study are appropriately cautionary, stating that achieved educational level is associated with access to kidney transplantation. It is reasonable to conclude that educational achievement is one aspect of the wider factor of socioeconomic status that accounts for the variation in transplant referrals and outcomes in the United States. However it is important to ask whether educational status is a likely explanatory variable influencing access to transplant. Is it plausible that a patient whose formal education is limited to multiplication tables or verb tenses is less likely to adhere to treatment regimens or to be selected by a physician for transplant evaluation than another patient who took calculus or literature in college? I suspect that educational status is as blunt an instrument in epidemiological research as socioeconomic status. One potential strategy to better assess the relationship between educational status and transplant access in this cohort is the use of propensity scoring to match individuals who are similar in most respects aside from education. Using this methodology, the authors could adjust for poorly measured factors that are linked with educational status or socioeconomic status; however, several researchers, including an author of this study, have stated that propensity scoring adds little to multivariate models that adequately incorporate relevant covariates.4 The authors correctly point out that many of the covariates available in this study for analysis, including comorbid conditions, may be on the causal pathway between educational status and illness and could potentially bias their findings. Moreover the factors adjusted for in the analysis did not include important contextual or ecological information that may have a role in the outcome of interest. It is true that using propensity scoring does not assure that study participants matched for their likelihood of having a certain exposure—in this case a certain educational status—are also matched on other unmeasured covariates. Yet, this approach is likely to be more effective in aligning participants who have similar social “circumstances” and thereby adjust for factors that might coexist with education and are not included in multivariable models.

A better predictor of health outcomes than achieved educational level may be health literacy. The Institute of Medicine report entitled Health Literacy: A Prescription to End Confusion has defined health literacy as the degree to which individuals can comprehend health information that they may need to make appropriate health decisions.5 The Institute of Medicine report made the point that educational achievement does not equate with health literacy and the latter should be measured and accounted for in the health care setting. Several tools exist for measurement of health literacy, including surveys such as the Test for Functional Health Literacy in Adults (TOFLA) and the Rapid Estimate of Adult Literacy in Medicine (REALM). Using such tools, health literacy has been shown to be a major determinant of health outcomes. For example, among patients with type 2 diabetes who have been tested using the TOFLA, those who score poorly are less likely to achieve tight glycemic control and are more likely to report retinopathy than those who score well.6 Similar findings have been reported for other chronic diseases.7, 8

Patients with ESRD face several daunting challenges when attempting to live with kidney failure; these include seeking access to and advocating for kidney transplantation. While the rates of organ donation vary widely, the prevailing standard is to make this option available to all those who are eligible. The process of gaining access to a transplant or placement on a waiting list requires a committed health care team, but also a motivated and well-informed patient who has the ability to be a major stakeholder in the process. The findings of Schaeffner and colleagues may not come as a surprise to the nephrology community, but we must recognize that education and more difficult to measure patient-specific factors, including health literacy, are often not modifiable. Therefore, our disease management strategies must adapt to the realities of our disease population and their needs.