1. Agreement in the types of data that occur in natural pairs. For example, in a trait like schizophrenia, a pair of identical twins is concordant if both are affected or both are unaffected; it is discordant if one of them only is affected. Likewise, the pairs might be non-identical twins, or sibs, or husband and wife, etc. 2. A negotiated, shared agreement between clinician and patient concerning treatment regimen(s), outcomes, and behaviors; a more cooperative relationship than those based on issues of compliance and noncompliance. [L. concordia, agreeing, harmony]
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n.
similarity of any physical characteristic that is found in both of a pair of twins.
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con·cor·dance (kən-korґdəns) [L. concordare to agree] in genetics, the occurrence of a given trait in both members of a twin pair, as opposed to discordance.Medical dictionary. 2011.