“There are known knowns; there are things that we know that we know,” then-defense secretary Donald Rumsfeld famously said in response to a question at a 2002 news briefing.

“We also know there are known unknowns. . . .” he added. “But there are also unknown unknowns, the ones we don’t know we don’t know.”

Rumsfeld—the principal subject of a new documentary, The Unknown Known, by Oscar-winning director Errol Morris—was addressing the case for war against Iraq. But when it comes to the case for improving the use of laboratory testing, the “known known” is fairly clear.

Overutilization is widely understood as a problem that blights American medicine, with lab testing no exception to the rule.

But there also is a “known unknown” in the world of test utilization—the extent of underuse, its effect on care and costs, and how to deal with it. How often do clinicians fail to order the tests that would improve diagnosis, prognosis, or management? And how can pathologists and their colleagues in the laboratory take action to improve test ordering if they lack the complete patient picture that would allow them to help clinicians spot the instances in which ordering more tests is the right answer?

My latest feature article in CAP TODAY. Read the whole shebang.