I think there are too many to choose from.

active diffusion control
adenylate cyclase
adrenal cortex
adult day care
affective disorders clinic
agar diffusion chamber
AIDS-dementia complex
albumin, dextrose, catalase Microbiology
Alzheimer’s disease centre
analog-to-digital computer
anchorage-dependent cell
anodal duration contraction (physiology)
anthracenedicarboxyaldehyde
antibody-dependent cytotoxicity
apparent diffusion coefficient
arginine decarboxylase
automatic data capture (Medspeak-UK)
average daily census
axiodistocervical Dentistry