Synonyms for Confirming (same or very similar meaning)
WordNet sense 1 (serving to support or corroborate):
collateral, corroborative, corroboratory, confirmative, confirmatory, substantiating, substantiative, validating, validatory, verificatory, verifyingWordNet sense 2 (furnishing support or assistance):
supportiveWordNet sense 3 (indicating existence or presence of a suspected condition or pathogen):
positiveFrom the ODE community, based on WordNetadd/edit