To directly examine whether social factors affect transplant recommendations, we surveyed a national random sample of adult and pediatric nephrologists. Random combinations of patient characteristics generated hypothetical case vignettes of children and adolescents with kidney failure, describing patient age, race, number of parents in the home, parents' educational level, and compliance. Physicians were asked whether or not they recommended transplantation for each of these case vignettes. With a 61% response rate, we found that race did not primarily affect pediatric renal transplant referral, however, the physicians' transplant recommendations varied in a graded fashion, with explicit labels describing parents' education and level of compliance. Children of more educated parents were more likely to be referred for transplantation. Patients described as ‘noncompliant’ were much less likely to be referred for transplantation than those labeled ‘compliant’. Furthermore, our analysis suggested a label of noncompliance had a stronger negative effect on transplant referral for white compared with black patients, while among patients labeled as compliant, white patients were statistically significantly more likely than black patients to be referred for transplantation. How do these findings shed light on the tangle of biologic, social and economic factors that contribute to ‘race-based barriers’ to kidney transplantation?
A number of authors have asserted that ‘sociocultural’ status, including educational attainment, influences medical decision making by health professionals (20,21). A patients' educational level may be known or subjectively assessed. As parents are responsible for carrying out the medical plan for pediatric transplant recipients, we included the parents' educational status in our case vignettes. Our study shows that when the level of parental education is made explicit, higher education is associated with increasing likelihood of referral for transplantation. Although little data exists directly measuring parental education in pediatric renal disease, among adult patients with ESRD substantial differences in the levels of education exist between black and white dialysis patients. In one large recent study, over 25% of black dialysis patients had not completed high school while only 17% of whites had less than a high school education (3). In that study, when the probability of referral for transplantation among blacks and white patients was adjusted for sociodemographic factors and type of dialysis facility, black–white differences became substantially smaller, suggesting that a large part of the observed racial difference could be attributed to differences in sociodemographic factors.
While labels of educational level were made explicit in our study, in clinical practice, patients' educational level is often subjectively assessed by their physician. Recent reports have shown that a physician's perception of a patients' education can be associated with patient race (22). Blacks are frequently perceived to be less educated than whites. Therefore, physician perceptions of level of parental education may correlate with race, and an increased referral rate for transplantation associated with higher levels of parental education may partly explain the previously described racial differences in referral for transplantation.
In our overall analysis, a label of noncompliance was the most important factor influencing transplant recommendations. Compliance, or adherence, to the immunosuppressive regimen is essential for long-term graft survival. The important consideration given to descriptions of compliance may therefore be appropriate in these case vignettes. In organ transplant recipients, noncompliance rates range between 20 and 50%, and at least in one study, 91% of patients who were noncompliant with medications suffered either graft rejection or death compared with 18% of compliant patients (20).
In our vignettes, cases were presented with labels of ‘compliant’, ‘questionably compliant’ or ‘not compliant’. In practice, subjective assessments on the part of the physicians would substitute for our explicit labels. Several studies have demonstrated that subjective physician assessments of compliance may be associated with race. In a study of the effect of race on a physician's recommendation for cardiac catheterization, physicians were asked to predict the likelihood that a patient would comply with therapy, and to judge the characteristics of patients believed to be predictors of patient compliance. Actors reading identical scripted symptoms played patients. In this study, black actor patients were deemed less likely to comply with therapy than whites (14). Another recent study of the effect of patient race and socioeconomic status on physicians' perceptions of patients, also showed that compared with white patients, black patients were deemed less likely to comply with medical advice, and less likely to participate in physician-prescribed rehabilitation (22). If physicians' perceptions of post-transplant compliance are not only important determinants of transplant referral, but also are associated with patient race, subtle differences in perceptions of compliance could contribute to systematic racial differences in access to transplantation. In our stratified analyses, when explicit descriptions of compliance were held constant, differences in transplant recommendations according to race existed among patients labeled as ‘compliant’. In this group, white patients were more likely to be recommended for transplantation than were black patients. This finding could be interpreted to show that among patients in whom physicians are confident of compliance, there is a bias against transplant recommendation for black compared with white patients. However, this association did not persist among those patients labeled as ‘questionably’ or ‘not’ compliant. It must also be cautioned that the multiple comparisons performed in our analysis may have raised to the level of significance a potentially random association between race, compliance and recommendation for transplantation.
The strengths of this study include the use of randomized, hypothetical case vignettes in which patient race, social and economic factors are randomly combined. In the study of actual dialysis patients, these factors are frequently closely linked, and their effects on referral for transplantation are difficult to separate. The experimental design of this study allowed us to isolate the effects of these characteristics on the nephrologists' treatment recommendations, as we used only vignettes of medically ‘appropriate’ transplant candidates with no contradictions for this procedure, and no stated patient preference. In analyses of observational patient data, it is difficult to tease out the relative contributions of patient preferences, physician recommendations and the nature of the interaction between the physician and patient, which cumulatively impact on treatment decisions in clinical practice.
Our conclusions are also strengthened by the national representation of the nephrologists in our sample. Stratified sampling by geographic location ensured that we sampled nephrologists from both urban and rural areas as geography may certainly influence treatment recommendations.
Our study has several limitations. Our response rate of 61% leaves open the possibility that respondents to our survey may differ in significant ways to nonrespondents and that our results will not be generalizable. We cannot judge the effects of the differential response of the pediatric compared with the adult nephrologists. However, transplant recommendations by the adult and pediatric nephrologists (82% vs. 78%) were similar. Additionally, our overall response rate surpasses the mean response rate of 54% for published physician surveys (23). Furthermore, the analyses comparing responders to nonresponders demonstrated no differences in response rate by geographic region. Although we saw that pediatric nephrologists were more likely than adult nephrologists to respond to our survey, this is likely related to the fact that the case vignettes included only patients up to 19 years of age. Although response rates were lower, the evaluation of the adult nephrologists' transplant recommendations in our survey was important to the generalizability of our results, as previous studies of USRDS data suggest that almost one-third of chronic pediatric ESRD patients are cared for in facilities that predominantly serve adults (24).
Although the use of case vignettes does not allow the clinician the wealth of clinical information gleaned in a genuine physician–patient interaction, and the response to the patient description on the printed page may vary from actual practice, the use of case vignettes is also a unique strength of our study. Case vignettes have been shown to approximate the gold standard of standardized patient interviews in studies focusing on the process of care provided in actual clinical practice (25).
It is important to remember that in this study of social factors affecting a nephrologist's transplant recommendations, the nephrologists surveyed recommended transplantation in an overwhelming majority (80%) of the cases presented to them. Our study suggests that nephrologists' perceptions of patient compliance and the level of parental education may impact transplant recommendations. Race did not directly affect transplant recommendations in this survey. However, if a physician's perception of patient compliance and education are linked with race, these factors could contribute to ‘race-based barriers’ to referral for transplantation. In disentangling the effects of race, parental education and compliance on nephrologists' recommendations for transplantation in hypothetical, clinically ‘appropriate’ transplant candidates, our study points to further research in the direction of targeted interventions to erase differential access to transplantation. These interventions may include efforts to eradicate education biases, and the development of standardized, objective measures of compliance with care as part of the transplant evaluation (26).