Why Do We Get Tests?

 

Why do clinicians order diagnostic tests? What do tests do for us?

Some simplified answers include:

-          Tests tell us what’s going on with the patient.

-          Tests are for protecting yourself legally.

-          Tests are standard practice for many situations.

Let’s take a step back and think about what tests do for our decision making process, because the above answers are oversimplified.

Any patient presents the clinician with a set of data. We take this data and put the pieces together like a puzzle. We give this data meaning through our medical knowledge and clinical experience. Once we have the enough pieces of the puzzle together and have the diagnosis, the treatment is usually straightforward.

Where do we get this data? The history, the physical exam, and finally testing.

Testing provides data that the history and physical cannot. Alternatively, the history and physical provides data that testing cannot. These sources often complement each other. Together they provide a more complete picture of the patient. Each specific source of data will have their own specificity, sensitivity, strengths, and weaknesses. As a clinician, it’s important to have a sense of all of these factors for each source of data we use.

Do we always need testing? No. We may not need testing at all depending on how clear the picture is with the history and physical exam.

When do we have enough data to have a clear picture of the patient’s diagnosis? To a certain degree, that can depend with each, individual clinician, and their comfort with diagnostic uncertainty. Diagnostic uncertainty pervades medicine. This is one reason why we have “styles” in medicine.

As far as responses to the answers given above,

-          Tests help us determine parts of what is going with the patient, but are rarely the complete story.

-          Documenting a clear clinical picture can be better legal protection, but sometimes the history and physical exam can provide a clear picture without tests.

-          Tests done because they are “standard practice” may be unnecessary from a purely medical decision making point of view, especially when you examine the logic behind them in a particular situation. Clinicians may still do them for reasons like outdated institutional guidelines, local tradition, etc.

If you want to learn about more about testing and medical decision making, feel free to check out my book: A Guide to Clinical Decision Making