Association between sex and kidney transplant referral, living donor contacts, waitlisting and kidney transplant: a population-based cohort study

Background — Studies from several jurisdictions suggest that compared to male individuals, female individuals are less likely to get placed on the waiting list for kidney transplantation and less likely to receive a transplant. However, we poorly understand where sex disparities arise within four key steps in the pathway to kidney transplant.

Objective — To measure how sex influences key steps to kidney transplantation.

Design — We conducted a population-based cohort study using linked administrative healthcare databases.

Setting — Ontario, Canada.

Patients — The study included people with kidney failure. This group comprised patients approaching the need for dialysis and those receiving maintenance dialysis from November 1, 2017, to December 31, 2021 (with follow-up to March 31, 2023). All patients had no recorded contraindications to receiving a kidney transplant.

Measurements — We assessed patient access to four key steps toward kidney transplant: (1) referral to a transplant centre for assessment; (2) they had a potential living donor contact the transplant centre for evaluation; (3) addition to the deceased donor waitlist; and (4) transplantation from a living or deceased donor. We examined each step separately.

Methods — We compared male and female individuals on the four steps in the kidney transplant process, using the incidence rate and cumulative incidence function (95% confidence interval [CI]). We used Cox proportional hazards analysis to examine the association between sex (using male as the reference group) and each transplant step, adjusting for patient characteristics. We also examined if age (<45, 45 to <55, 55 to <65, and 65 to 75 years) changed the relationship between sex and access to transplantation.

Results — We included 17,993 patients with kidney failure (11,076 male and 6,917 female individuals). Of these, 15,238 entered the cohort approaching the need for dialysis, and 2,755 entered already receiving maintenance dialysis. Over follow-up, 4,945 (32.5%) patients in the approaching the need for dialysis cohort started dialysis. Female individuals had a significantly lower rate of referral to a transplant centre for assessment than male individuals (9.35 vs 10.91 referrals per 100 person-years; adjusted hazard ratio [aHR] 0.86 [95% CI: 0.81, 0.92]). The disadvantage female individuals faced in transplant referral increased with age (age 65 to 75 years, aHR 0.73 [95% CI: 0.64, 0.84]; P-value for interaction <0.001). After we adjusted for patient characteristics, we found no significant sex-based differences for any other step in the transplant process, including living donor contact, waitlisting, or transplant. For all outcomes, a significant interaction was found between age and sex (P-value for interaction < 0.001). The kidney transplant access disadvantage for female compared to male individuals was greater in older age groups (for example, aged 65 to 75 years).

Limitations — We could not adjust for all factors influencing transplant access (for example, frailty, smoking status, and patient preference).

Conclusions — Female individuals who were likely eligible for transplant were significantly less likely to be referred to a transplant centre for assessment. This disadvantage increased with age. However, we observed no significant differences between male and female individuals for other steps in the transplant process. Further research should examine possible barriers to transplant referral among female individuals.