Docs formulate a list of differential diagnoses. Based on the list of possible causes of a particular problem, docs order diagnostic tests and procedures.
When I started in medicine over 30 years ago, we called the process ”rule out,” meaning we ordered tests to narrow the list of possible diagnoses until we found the right one. The more complex the disorder, the more tests are ordered.
In reality, docs don’t own a crystal ball. If they did, they would know which tests were going to be positive (necessary) and which were going to be negative (unnecessary). Since docs don’t have the ability to see into the future accurately, diagnoses and test ordering boils down to an educated guess.
To make matters worse, diseases are dynamic, forever changing. An eighteen year old comes in with a severe tonsillitis. Her mono test is negative.
Obviously, the test was not necessary since the test is negative. Right? Wrong! Ten days later she is seen again by another doc. Her mother states, “I took her to Dr. X 10 days ago and he didn’t know what he was doing. He wasted my money on a negative mono and strep test. Can you help her?” After explaining that a negative mono test is meaningless (as Dr. X had previously warned her), the new doc orders a repeat test which is now strongly positive. Diseases are dynamic and our ability to diagnose them correctly often improves with time as the disease evolves and changes.
Read the full piece here.