Guidance

Chapter 1: introduction

Updated 21 May 2024

This guidance updates and replaces the ‘Guidance on the microbiological safety of human organs, tissues and cells used in transplantation’ issued in February 2011.

SaBTO’s role is to advise ministers of the UK government and the devolved administrations as well as UK health departments on the most appropriate ways to ensure the safety of blood, cells, tissues and organs for transfusion and transplantation.

This guidance should be read with reference to other current SaBTO guidance.

The emergence of the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) in late 2019 has had significant implications for the donation of human organs, tissues and cells used in transplantation. This is discussed in Annex 1.

This guidance has been written by a working group (members are listed in Annex 2). Other publications on this subject were taken into consideration during the preparation of this document.

The underlying principle running through this guidance is that the risk of an infection being passed on through transplanted organs, tissues and cells be kept to an acceptable minimum. What constitutes an acceptable minimum is dependent on the balance of risk and benefit for the potential recipient in terms of either receiving the proposed transplant or going without that specific transplant. In urgent life-preserving situations, a higher risk of infection may be acceptable while stricter controls are needed in non-urgent situations and for transplants aimed at improving a patient’s quality of life rather than saving it. In all situations the potential recipient, or their proxy, should provide full informed consent that must include discussions regarding the potential for transmission of infection.

The section ‘Examples of human substances covered by this guidance’ (below) contains a list of most of the organs, tissues and cells (haematopoietic, reproductive and other cells) covered by this guidance. This guidance does not cover substances of non-human origin - for example, xenotransplantation.

The broad principle regarding minimisation of transmission of infection also applies to the source human tissues and cells cultured in a laboratory before transplantation and to manufactured products or services that use human cells or tissues.

Reproductive cells, embryos and embryonic stem cells and haematopoietic stem and progenitor cells are within the remit of this guidance. However, the microbiological safety and quality of human blood and blood components and blood products is covered elsewhere (Transfusion guidelines).

The guidelines set out the main recommendations covering microbiological screening of organ, tissue and cell donors together with resulting actions to take following the identification of an infected (or potentially infected) donor.

For organ donors and deceased tissue donors, the information required for assessing an organ donor’s risk of harbouring an infection are set out in the NHS Blood and Transplant patient assessment form (PA1).

For haematopoietic and therapeutic cell donors, guidance on the minimum requirements for assessment of suitability to donate can be found in the current edition of the FACT-JACIE International Standards for Hematopoietic Cellular Therapy Product Collection, Processing, and Administration. The World Donor Marrow Association provides guidance on the minimum standards by which unrelated haematopoietic stem and progenitor cell donors should be assessed. Neither set of guidelines is intended to supersede local laws or requirements of national legislative bodies.

The recommendations and guidance contained within this document reflects good practice in accordance with available evidence, supplemented by expert opinion where published evidence is lacking. It is also acknowledged that the advice contained within may need to be modified as a consequence of clinical developments or emerging infections.

This document will only be published in electronic format. Sub-sections will be revised at intervals to reflect changes in knowledge and perceived risk of transmission of infection. Clinicians should consult the most up to date version available on the SaBTO website and other sites including NHS Blood and Transplant and NHS Organ Donation and Transplantation.

To aid transplant clinicians in decision-making when considering the use of organs for transplantation from donors with infection, malignancy and other potentially transmissible disease, SaBTO has devised a quick reference guide or aide memoire as an online application. The guidance in the aide memoire and this document are updated in tandem.

Examples of human substances covered by this guidance

Organs

Examples include:

• bowel
• heart
• kidney
• liver
• lung
• pancreas
• composite tissue transplants - for example, face or hands
• regenerated organs

Tissues and cells

Examples include:

• bone
• cartilage
• cornea or sclera
• heart valves
• skin
• tendons
• vascular tissue
• amnion
• menisci
• pancreatic islet cells [note 1]
• ocular stem cells - that is, limbal [note 2]
• chondrocytes
• keratinocytes [note 2]
• induced pluripotent stem cells (iPS)
• immature ovarian or testicular tissue

Note 1: although islet cells are processed (isolated and purified), they are subject to time constraints akin to organs.

Note 2: limbal stem cells, keratinocytes, chondrocytes, iPS and embryonic stem cells may be cultured and expanded in the laboratory and should be considered as tissues for the purposes of microbiological testing. Cells used as feeder layers at any stage in the process are considered to fall within this guidance and also require microbiological testing including for potential zoonotic infections where feeder cells are of non-human origin. In addition, some of these materials may also be considered advanced therapeutic medicinal products (ATMPs) and are therefore regulated by the appropriate guidelines. In addition, the statutory requirements set out in The Human Tissue (Quality and Safety for Human Application) Regulations 2007 still apply to the procurement, donor selection and testing of the starting tissue.

Haematopoietic stem and progenitor cells (HSPCs) and therapeutic cells (TCs) [note 3]

Examples include:

• HSPCs collected from bone marrow (HSPCs, marrow)
• HSPCs collected from peripheral blood (HSPCs, apheresis)
• HSPCs collected from umbilical cord blood (HSPCs, cord blood)
• donor lymphocyte infusions and other TCs
• embryonic stem cell lines derived from human embryos created for treatments excluding fertility
• embryonic stem cell lines intended for clinical use derived from human embryos initially created for fertility treatment

Note 3: TCs include a wide range of selected and cultured products including T-cells, natural killer cells, mesenchymal stem cells, cytotoxic T-lymphocytes, T-regulatory cells, tumour derived cells.

Reproductive cells

Examples include:

• gametes (sperm and eggs)
• embryos created in vitro

See a list of all chapters in this guidance