**1. Introduction**

Living-donor kidney transplantation is the optimal treatment for most people with kidney failure in terms of patient survival, graft survival and quality of life [1–6]. The healthcare costs associated with living-donor kidney transplants (LDKTs) are less than for dialysis and deceased-donor kidney transplants (DDKTs) [7,8]. The medium-term risks of donating a kidney are small [9–12], and the quality of life of donors usually returns to pre-donation levels after donation [13,14].

Only 28% of all kidney transplants performed in the UK each year are from a living donor [6], a proportion below that of the USA and the Netherlands [15]. Individuals from Black, Asian and minority ethnic populations in the UK appear to be particularly disadvantaged as they are less likely to receive a LDKT compared to White people with kidney disease [16,17]; only 18% of living donor kidney transplant recipients in the UK between April 2019–March 2020 were from Black, Asian and minority ethnic group backgrounds, despite individuals from these groups constituting 36% of the kidney transplant waiting list [6]. Improving equity in living-donor kidney transplantation has been highlighted as a UK and international research priority by patients and clinicians [18,19].

Specific religious and cultural beliefs, as well as a lack of specific knowledge about donation, have been identified as reasons for ethnic disparity in deceased organ donation [20,21]. The barriers specifically encountered by Black, Asian and minority ethnic group patients in accessing LDKTs in the UK are not well described.

We have previously investigated reasons why individuals who start assessment for kidney donation do not go on to donate in the UK. In this multicentre study, individuals from Black, Asian and minority ethnic groups were more likely to withdraw from donor evaluation [22]. However, transplant candidates and their families often make decisions regarding the suitability of potential donors before they make contact with hospital services. The perceptions of transplant candidates, regarding the suitability of family members for donation, function as an initial stage of donor screening. Transplant candidates are often uncomfortable broaching the subject of organ donation and make assumptions as to why individuals may or may not be able to donate. Transplant candidates may perceive barriers to donation that prevent potential donors from starting donor assessment. It is important to understand these perceptions in order to fully understand barriers to living-donor kidney transplantation. In this multi-centre questionnaire-based study, we investigated the reasons why family members were perceived by kidney patients as unsuitable as living kidney donors, comparing responses between individuals from White and Black, Asian and minority ethnic groups. Ultimately we aimed to identify potentially modifiable barriers to LDKTs specific to the UK Black, Asian and minority ethnic populations that could be targeted to redress the observed disparity.

#### **2. Experimental Section**

#### *2.1. Study Design*

We designed this multi-centre questionnaire-based study to investigate the patient-identified and reported reasons potential donors did not donate. We collected both quantitative (checklist item selection) and qualitative (free-text) questionnaire data to gain a greater understanding than that provided by one data type [23]. We collected data on whether participants asked potential donors to donate, whether any o ffered, and whether any started donor assessment. We collected data from both LDKT and DDKT recipients—LDKT recipients may have had other potential donors who volunteered but did not donate, and we wanted to ensure we captured the reasons for non-donation for all. We compared the responses of Black, Asian and minority ethnic individuals with White individuals to identify barriers that might be specific to Black, Asian and minority ethnic populations and therefore might explain the observed ethnic inequity.
