What is it about?

Best practice guidelines recommend the use of masking (also known as blinding) to increase the rigour and reproducibility of in vivo research. Masking involves concealing which experimental group animals are part of, or the treatment they receive, from the people running the study, caring for the animals and analysing the data. Implementing it in practice is often not straight forward. This study investigated current practices in various labs in the UK and identified a number of barriers that hindered researchers from using masking in their in vivo studies, from staff resources and operational constraints through to animal welfare concerns or knowledge gaps. The study also presents different strategies to help overcome or reduce the effect of these barriers at different stages of an experiment. To highlight how masking can be implemented in real experiments a case study with masking at several steps is included.

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Why is it important?

Masking is a strategy to reduce the risk that researchers subconsciously influence research results by inadvertently introducing difference between treatment groups. For example, in a pain model being more cautious in the handling with disease induced animals. However, implementing it is not always simple and requires careful planning. It is not realistic to expect every animal experiment to be fully masked throughout but most studies can relatively easily use some form of masking at some stage during the experiment; progress can be achieved with small incremental changes. This study offers practical solutions to common challenges.


“The use of masking is frequently considered in an all or nothing perspective – it has either been used or it has not. In reality, experiments are on a continuum where masking can be applied to selected stages of the experiments, using strategies with various levels of stringency and complexity. This paper is the first to ask researchers how they use masking in practice in their animal experiments and what barriers they have encountered. It also provides strategies and insight into how we as a community can move forward.” Esther Pearl, Programme Manager - Experimental Design, NC3Rs

Natasha Karp
AstraZeneca plc

Read the Original

This page is a summary of: A qualitative study of the barriers to using blinding in in vivo experiments and suggestions for improvement, PLoS Biology, November 2022, PLOS,
DOI: 10.1371/journal.pbio.3001873.
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