diagnostic

adj. relating to or used in diagnosis, relating to or used in the identification of a disease from its symptoms

In general, diagnosis (plural diagnoses) has two distinct dictionary definitions. The first definition is "the recognition of a disease or condition by its outward signs and symptoms", while the second definition is "the analysis of the underlying physiological/biochemical cause(s) of a disease or condition".
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Di·ag·nos·tic adj. 1. Of, relating to, or used in a diagnosis. 2. Serving to identify a particular disease; characteristic. n. 1. [more]Diagnostic - Community and Resources

Adjective
1. concerned with diagnosis; used for furthering diagnosis; "a diagnostic clinic"; "a diagnostic reading test"; "diagnostic information"
(pertainym) diagnosis, diagnosing
2. characteristic or indicative of e.g. a disease; "a diagnostic sign of yellow fever"; "diagnostic information"; "a rash symptomatic of scarlet fever"; "symptomatic of insanity"; "a rise in crime symptomatic of social breakdown"
(synonym) symptomatic, symptomatic of(p)
(similar) characteristic

n. diagnosis, process of identifying a disease from its symptoms, conclusion following a diagnostic exam