Key considerations for different types of interventions used in an in vivo experiment.




An intervention is a process which a group of animals (or experimental units) is subjected to, such as a surgical procedure or a drug injection. 

Considerations for different types of intervention

When planning your experiments, you will need to consider different things depending on type(s) of intervention involved: 

  • Pharmacological intervention – drug and dose, along with mode of administration.
  • Surgical intervention – anaesthetic and analgesic regimen, duration of anaesthesia and anticipated success rate.
  • Pathogen infection – infectious agent and dose load.
  • Euthanasia – method used and tissues collected at autopsy.

An experiment can involve multiple types on intervention.

Representing different interventions in the EDA

In your experiment diagram in the EDA, each different type of intervention has a distinct intervention node: surgical intervention, pharmacological intervention, pathogen infection and euthanasia. For interventions which do not fit into any of the aforementioned categories, the node ‘other intervention’ can be used. For example, to represent an environmental stimulus in a behavioural assay (such as conditioning, scruffing or exposure to light) or tissue processing steps (such as microscopy or immunohistochemistry).

Distinct types of intervention nodes capture different information, allowing you to add information relevant to that specific type of intervention. Typically, an experiment contains multiple nodes of the same type, as treatment and control groups are subjected to variations of the same intervention. If the intervention defines the different categories of a variable of interest, then duplicates of the variable categories nodes should be used to tag the intervention nodes, as seen in the image below.

Partial EDA diagram showing an experiment involving a vagotomy surgery and a sham control where variable category nodes have been used to make it clear which group will undergo which surgery.

An experiment can contain multiple types of intervention. For example in Example 4 (see image below) the first intervention involves mice placed in a cage with a running wheel – this is represented with an other intervention node and, as the intervention is different in treatment animals (the running wheel rotates) and control animals (the running wheel is fixed), two distinct nodes are used. All animals are then euthanised – as treatment and control animals go through the exact same procedure this is represented by a single euthanasia intervention node.

Partial EDA diagram showing an experiment with some interventions that differ between the groups and some that are the same.


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First published 10 January 2014
Last updated 31 October 2023