Identification of concepts of importance for the assessment of internal validity of in vitro toxicology studies using a modified Delphi technique

Context In vitro toxicity studies are increasingly being included as evidence in systematic reviews and chemical risk assessments. INVITES-IN, a tool for assessing the internal validity of in vitro studies, is under development in a process consisting of four consecutive studies. Study One in the creation of INVITES-IN was the development of an "item bank" database of 405 concepts ("items") of potential relevance for assessing the internal validity of in vitro toxicity studies. The items were gathered from both focus group discussions and a purposive literature sample. In this paper we present the second study in the creation of INVITES-IN, i.e. the methods and results for identifying items for consideration when assessing the potential for bias in an in vitro study.