Formalization of indicators of diagnostic performance in a realist ontology

We present a formalization of indicators of diagnostic performance (sensitivity, specificity, positive predictive value and negative predic-­‐ tive value) in the context of a realist ontology. We dissociate the indica-­‐ tors of diagnostic performance from their estimations and argue that the former should be represented in a first place in biomedical ontolo-­‐ gies. Our formalization does not require to introduce any possible, non-­‐actual entities -­‐ like the result a person would get if a medical test would be performed on her -­‐ and is therefore acceptable in an ontology built in a realist spirit. We formalize an indicator of diagnostic perfor-­‐ mance as a data item that is about a disposition borne by a group; the diagnostic value of this indicator is given by the objective probability value assigned to this disposition.