Ethical issues in the use of leftover samples and associated personal data obtained from diagnostic laboratories

Diagnostic laboratories are an integral part of the research ecosystem in biomedical sciences. Among other roles, laboratories are a source of clinically-characterized samples for research or diagnostic validation studies. Particularly during the COVID-19 pandemic, this process was entered by laboratories with different experience in the ethical management of human samples. The objective of this document is to present the current ethical framework regarding the use of leftover samples in clinical laboratories. Leftover samples are defined as the residue of a sample that has been obtained and used for clinical purposes, and would otherwise be discarded. Secondary use of samples typically demands institutional ethical oversight and informed consent by the participants, although the latter requirement could be exempted when the harm risks are sufficiently small. However, ongoing discussions have proposed that minimal risk is an insufficient argument to allow the use of samples without consent. In this article, we discuss both positions, to finally suggest that laboratories anticipating the secondary use of samples should consider the adoption of broad informed consent, or even the implementation of organized biobanking, in order to achieve higher standards of ethical compliance which would enhance their capacity to fulfill their role in the production of knowledge.