ARBITRARY EXCLUSION BIAS:

A bias that arises due to the exclusion of studies for non-scientific reasons from systematic reviews. Arbitrary Exclusion Bias may result in a Publication Bias (i.e. Selection Bias) in any studies which involve the systematic, and controlled review of previous research.

It is estimated that the medical literature contains a substantial number of reviews which have excluded papers for non-scientific reasons, despite these papers meeting the inclusion and exclusion criteria defined by investigators. These reasons may include; the article was not available, was in the wrong language, was published in the wrong year, was a duplicate study, or other unknown reasons¹.

Lack of universal availability (i.e. open access) of research due to pay-walls may contribute to Arbitrary Exclusion Bias. Investigators from less-wealthy research institutes may not be able to afford the costs of obtaining article copies from large publishers, and thus may be forced to exclude these papers; affecting the quality of science. Also see: Publication Bias, and Selection Bias.

Reference:

1. Edinger T, Cohen AM. A large-scale analysis of the reasons given for excluding articles that are retrieved by literature search during systematic review. AMIA Annu Symp Proc. 2013;2013:379-87. (Link to Reference)