# Specificity

The frequency that a test for paratuberculosis is NEGATIVE when animals are NOT infected: the true-negative rate. Tests on NONinfected animals are either true-negative or false-positive. Diagnostic specificity as described here must be distinguished from analytical specificity: the ability of an assay to distinguish between similar analytes (things being measured). Example: the ability of an assay to distinguish M. avium subspecies avium (MAA) from MAP is the analytical specificity of the assay.