Discount posts fill the phone with callers who never arrive. A structure that fills the machine instead.
Price-led advertising for imaging and pathology attracts the most mobile, least loyal segment of the market, and trains everyone else to wait for the next offer. It also puts you in a bidding war you cannot win against a larger chain.
Advertise the things a patient cannot compare on a rate card: how fast the report arrives, who reports it, whether the machine is current, and whether a home collection is available in their area.
Then segment by referral pattern. A campaign aimed at patients holding a prescription behaves nothing like one aimed at annual health checks, and pooling them hides which of the two is actually paying.