INCORPORATION BIAS:
A bias relevant to diagnostic accuracy studies: When the results of the diagnostic test under study (index test) is used in establishing the final diagnosis of patients instead of the gold standard test (reference test)1. Incorporation Bias will most likely increase the amount of agreement between the index test results and the reference test results; since the overall proportion of patients with the same diagnosis on the index test and gold standard will be higher (similarity across tests is preferred in diagnostic accuracy studies). This bias is analogous to misclassification of the exposure in case-control studies; the exposure in this scenario being the diagnostic tests under comparison. To avoid this bias, the final diagnosis for all patients should be defined by the results of the gold standard test2. Also see: Information Bias, and Misclassification Bias.
References:
1) Whiting P, Rutjes AW, Reitsma JB, Bossuyt PM, Kleijnen J. The development of QUADAS: a tool for the quality assessment of studies of diagnostic accuracy included in systematic reviews. BMC Med Res Methodol. 2003;3:25. (Link to Reference)
2) Bossuyt PM, Reitsma JB, Bruns DE, Gatsonis CA, Glasziou PP, Irwig L, Lijmer JG, Moher D, Rennie D, de Vet HC, Kressel HY, Rifai N, Golub RM, Altman DG, Hooft L, Korevaar DA, Cohen JF. STARD 2015: an updated list of essential items for reporting diagnostic accuracy studies. BMJ. 2015;351:h5527. (Link to Reference)