The Perils of Indiscriminate Screening Tests

In a discussion thread on diet and blood tests, Dr. Doug McGuff made a very important observation about the dangers of government-driven practice guidelines and various "screening tests":

My major thesis is one against "screening". Unless you are feeling poorly and have a reason to check on a given body system (thyroid, kidney, adrenals or whatever) you should not do it. Without an increased pre-test probablility the risk of a false positive goes up.

These tests are not just "right or wrong", whether they are right or depends on whether the test "sets its sights" toward picking up positives (sensitivity) or negatives (specificity). No matter which way you set your sights, the more you get of one, the less you get of the other AND whether the test is going to give you information actually depends on if you have an elevated risk of having disease (pre-test probability).

If you have a false positive test result, and then go chasing after it (or worse, treating it) you can incur more morbidity and mortality than if you had never checked on it. For most tests and treatments in medicine the number needed to harm is lower than the number needed to treat.

When I order a Chem 18 (comprehensive metabolic panel) in the ER for an elderly person that has been vomiting for 4 days and is clinically dehydrated with jaundiced eyes, that has an elevated pre-test probability. Ordering a Chem 18 in a doctors office on a patient that is feeling well and is there for a yearly physical is just stupid.

Government health care is driving this herd mentality [emphasis mine - PSH], and most doctors I know simply do not understand this concept. It is a positively reinforced loop that is now withholding payments to doctors unless they do ridiculous stuff that the literature (and common sense) say is stupid.

Many doctors today (especially the more recently minted ones) cannot practice without referring to the i-phone to follow some government-mandated template. When residents rotate with me I collect all i-phones and digital technology at the beginning of the shift and smile as almost all become paralyzed with fear because they have not memorized anything useful.

Get yourself a concierge doctor that does not participate with government payors. Most are cheap ($35 bucks per visit) and are free to practice as they see fit. Force and threats really do paralyze the mind, especially in medicine.

Doug McGuff, MD