The more the merrier? Scoring, statistics and animal welfare in experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is a frequently used animal model for the investigation of autoimmune processes in the central nervous system. As such, EAE is useful for modelling certain aspects of multiple sclerosis, a human autoimmune disease that leads to demyelination and axonal destruction. It is an important tool for investigating pathobiology, identifying drug targets and testing drug candidates. Even though EAE is routinely used in many laboratories and is often part of the routine assessment of knockouts and transgenes, scoring of the disease course has not become standardized in the community, with at least 83 published scoring variants. Varying scales with differing parameters are used and thus limit comparability of experiments. Incorrect use of statistical analysis tools to assess EAE data is commonplace. In experimental practice the clinical score is used not only as an experimental readout, but also as a parameter to determine animal welfare actions. Often overlooked factors such as the animal's ability to sense its compromised motoric abilities, drastic though transient weight loss, and also the possibility of neuropathic pain, make the assessment of severity a difficult task and pose a problem for experimental refinement.