3Rs search methods

Searching for 3Rs methods: a needle in a haystack?

According to the European Directive 2010/63/EU on the protection of animals used for scientific purposes, animal testing is not allowed unless there is no possible alternative. To ensure this, the principle of the 3Rs (Replacement, Reduction and Refinement) should be considered at all times (article 4). In order to implement the 3Rs, scientists have to be aware of the 3Rs methods available.

Scientists are familiar with searching for literature on their subject of interest. Searching specifically for 3Rs methods, however, is something which may require specific search skills. There is a lot of information available, so how to make sure you find everything you are looking for? With this article we hope to provide you with some tools that facilitate the search for 3Rs methods. This article is based on the EURL ECVAM Search Guide, which provides a search strategy for 3Rs methods and might be of great help.

Developing a search strategy

Before starting a search for either one of the 3Rs methods, it is important to develop a search strategy. Important parts of this strategy are a search question, keywords and a list of potential information sources. All searches start by the formulation of a proper search question and (a combination of) keywords.

A search can either be very broad or very specific. It is smart to start with a specific question in a 3Rs environment by using a value-added database (the top of the pyramid, figure 1 below). Another start may be the 3Rguide.org website (see "Information Sources"). By starting the search in such a 3Rs context, information about 3Rs methods can be obtained much more easily than in a broader context. It helps to structure the search and provides a good start. After this step, the search can be extended to more broad-coverage databases with the use of some limitations or specific keywords, such as the MeSH term ‘animal use alternatives’ in PubMed. If you want to know more about the use of MeSH terms, use the different instructions and tutorial on the website of PubMed (see More information).  

Note! When searching in a database, a thesaurus can be very helpful to identify relevant/correct key words and their spelling. PubMed has its own thesaurus (MeSH terms), which can be used also separately in order to identify synonyms for key words. Like with all other literature searches, it is important to use Boolean operators (AND, OR, NOT) and wild cards (?, *, “…”) in the correct way.

When starting a search for 3Rs methods, the first thing to do is to look for replacement methods. Thereafter, attention should be paid to reduction and refinement. For each of the 3Rs, a separate search question should be addressed.

Figure 1: the pyramid for 3Rs searching of EURL ECVAM. Source: EURL ECVAM Search Guide 2013 (1)

Points of attention

The following points of attention should be kept in mind when searching for 3Rs methods:
- are there in vitro studies?
- are there studies with less sentient animals (e.g. invertebrates)?
- which animals are sensitive to the treatment?
- what statistical methods to use?
- is there application of analgesia and anesthesia?
- what humane endpoints are used?

7 steps to successful searching

The EURL ECVAM Search Guide describes seven steps which can be used for successful searching. By following these steps a systematic and structured search can be performed and the amount of information missed is minimalized.

Start with a sheet of paper ►

1. State of the art, define what you are looking for
2. Field of investigation, objective, method
3. Choosing information resources
4. Formulate search terms


Continue with databases/websites ►

5. Start with a simple question in a 3Rs context (e.g. use 3Rguide, AnimAlt-ZEBET)
6. Use broader context with 3Rs limitations (PubMed) 
7. Broaden search horizon, use less specific terms and more synonyms


Searching for 3Rs methods should be seen as a serious task which takes time. It is important to search in a structured way by using correct search terms and different information sources. Involving an information specialist could be helpful. Last but not least: document what you do and when, so that somebody else can repeat your search.