Patients who find time to ask their doctors about the cost of a proposed test or treatment are often wasting their time. Medical education traditionally avoids the subject, and medical billing is probably just as puzzling to physicians as it is to patients.

Doctors in training at the University of California, San Francisco, saying it’s “increasingly apparent” that they need to learn about medical costs, set out two years ago to teach themselves about the subject.

In an article just published in JAMA Internal Medicine, three young doctors describe the simple program they designed to promote cost-awareness among their colleagues and to reduce inappropriate care.

To do this, they had first-year residents compare evidence-based guidelines for certain conditions — headache, chest pain, low back pain, etc. — with the actual itemized hospital bills for recent patients.

Those results were shared with medical students, residents and the rest of the medical team at monthly lunches. Professional recommendations were compared with local reality.

For instance? They found that an otherwise healthy man, with two weeks of lower back pain, had been subjected to $10,821 worth of tests, imaging and drugs. If the American College of Physicians guidelines for appropriate care had been followed? It would have been $908.

The authors are not sure whether they’ve changed practices or costs yet, but they have changed attitudes. They note that doctors, in discussing individual cases, are now talking about the evidence for appropriate care.