biopsy vs diagnostic assay

biopsy and diagnostic assay both are nouns.

Word	Noun	Adjective	Verb	Adverb
biopsy	Yes	No	No	No
diagnostic assay	Yes	No	No	No

As nouns, diagnostic assay is a hypernym of biopsy; that is, diagnostic assay is a word with a broader meaning than biopsy:

biopsy: examination of tissues or liquids from the living body to determine the existence or cause of a disease
diagnostic assay: an assay conducted for diagnostic purposes

Other hypernyms of biopsy include diagnostic test.

biopsy (noun)	diagnostic assay (noun)
examination of tissues or liquids from the living body to determine the existence or cause of a disease	an assay conducted for diagnostic purposes