MULTIPLY USED SUBJECTS BIAS:

A bias relevant to studies of knowledge synthesis (e.g. systematic reviews), that occurs when results from the same subjects are reported in multiple, different studies in the literature, when in fact they are only part of one study¹.

Multiply Used Subjects Bias refers to a consequence of Multiple Publication Bias; when subjects are double-counted in a review study, and thus excessive (unfair) weight is given to the results of these patients vs. others, when the data from the literature is combined in a meta-analysis. Thus, Multiply Used Subjects Bias describes a type of Selection Bias, and leads to invalid estimated associations between exposures and diseases. Also see: Multiple Publication Bias, Duplicate Publication Bias, and Publication Bias.

Reference:

1. Felson DT. Bias in meta-analytic research. J Clin Epidemiol. 1992;45(8):885-92. (Link to Reference)