My teachers in medical school and residency did not take kindly to me ordering extra tests for patients.
You don't order tests that you don't need, they would tell me. Because when you're not following a logical path, but just poking around for what might come up, you can end up with bad conclusions, bad results, and wasted resources.
However, a recent article in the New York Times reminded me that medical providers are "tricked", guided, and incentivized to order extra tests at every turn. Dr. Zuger looks at how, these days: "Guidelines mandate tests, and patients expect them; abnormal tests mean medication, and medication means more tests."