To the Editor.
—I believe there is a potential for bias in the study of Port et al1 that has not been addressed.My primary concern is that the authors do not stratify patients for comorbid disease states that are known to affect survival.2,3 Their presumption must be that since all patients passed the screening examinations for renal transplant wait-listing, they had equal comorbidity. I believe this assumption may be false. Although most major organ system diseases would be eliminated, some would not. Additionally, comorbid disease states acquired after screening put wait-listed patients into higher risk categories. These higher-risk patients may have been passed over one or more times, yet remain on the active waiting list in the hope that they will eventually become well enough to undergo renal transplantation.An additional mechanism that could explain why sicker patients remain wait-listed and are withheld a renal allograft relates