Climate change and diagnostic samples - Opening Pandora's (post) box

Objectives: To reflect on how climate change is reshaping the practicalities of diagnostic testing, using the UK's COVID-19 home-based testing programme as a case study, and to call for an urgent review of international standards governing the transport of biological samples. Study design: Narrative-based analysis drawing on operational experience during the UK National Testing Programme's response to COVID-19. Methods: We examine the design and implementation of a large-scale home testing model for COVID-19, which relied on the routine postal service to transport biological samples from homes to laboratories. These samples were transported without temperature control, across widely varying environmental conditions. This approach tested the limits of existing logistical assumptions and exposed critical regulatory gaps. Results: Despite the lack of temperature-controlled logistics, the UK's home testing programme functioned at scale, with internal validation assuring sample stability during both winter and summer extremes. However, this success occurred in the absence of any applicable international standards—such as ISO guidelines—that account for environmental factors in postal transport of biological samples. The experience highlighted a significant blind spot in regulatory frameworks, which currently assume controlled conditions that do not reflect real-world practice in emergency or climate-affected contexts. Conclusions: The changing climate and evolving models of healthcare delivery—particularly the move toward near-patient and home-based diagnostics—require a rethinking of how we assure the quality and reliability of biological samples in transit. Existing international standards are no longer fit for purpose in this regard. There is an urgent need to acknowledge environmental resilience as a core requirement in diagnostic logistics, and to develop new standards that are robust to the realities of climate variability and decentralised healthcare.