Thursday, July 9, 2015

The stethoscope – “it’s not a lie if you believe it.”

The skillful use of the stethoscope is a key element of the physical exam. Introduced in 1816, it afforded an unprecedented “view” inside the body. Since then it has evolved to become synonymous with being a physician (as well as nurse, paramedic,  tech, etc. 
But technology has progressed since Laënnec pressed his crude prototype against the chest of his first patient. We have discovered what electromagnetic radiation can reveal in an x-ray; we discovered that subatomic particles can be excited in a magnetic field, producing images of exquisite detail. And we discovered, uh, sound.  {Citation needed}

But regardless of all these new technologies, we all keep carting around our space-age versions of Laënnec’s hollow wood stick, draped around our necks, ready to bonk us in the eye if we make any sudden moves.   Why?

We all occasionally joke that these diagnostic devices serve mostly as “doctor jewelry,” and that we will always use a CXT, CT, MR, or whatever, to confirm our auscultations. However, if the conversation turns serious, we will solemnly avow the sacrosanct role of the hollow stick. “Nothing can replace a thorough Hx and P,” we intone, “nothing.”

We are, in that moment, the most harmful species of liar – the liar that believes the lie.

"Jerry, just remember. It's not a lie... if you believe it."
We need to stop, take a deep breath, look ourselves in the eye, and admit that we have not been truthful with thine own self. Dare to say the following; first while alone in your locked bathroom, then in a safe 12-step environment, and then eventually in public:

The stethoscope is a vestigial element of the physical exam, and ought to be retired.

Sort of the tone I'm shooting for.

First off, the physical exam in general is not that helpful.

Accordingly, the stethoscope is a vestigial element of a whole ritual of limited utility. In one study, the history was 20 times more useful than the physical exam. Heck, just using the ECG, CXR, and basic labs was more useful than the physical exam! In another study, looking at the ability to diagnose nerve root compression in back pain, the exam only improved the accuracy marginally, budging the AUC from 0.8 to 0.83. (OTOH, in appendicitis, tenderness in the RLQ kind of blows history out of the water...)

Second, the stethoscope sucks (or blows?)

While revolutionary in its day, the 'scope has seen its diagnostic performance plummet as medicine progressed. Pneumonia provides the best example of the limited contemporary accuracy of the stethoscope.

A systematic review in the Emergency Medicine Journal concluded that "pneumonia cannot reliably be confirmed or excluded by auscultation, or indeed physical examination, alone.” The most recent study in that review looked at patients coming into the ED with “chest symptoms,” and looked at how the diagnostic impression changed from pre- to post-auscultation, and then post-discharge. The vast majority of the time, about 95%, the clinical impression did not change after using the sacred hollow stick
Might have better luck with a Harry Potter replica wand.
Pneumonia, in particular, was diagnosed correctly in 45% of patients with history alone, and only improved to 49% after the exam.

An earlier study looked only at CXR-verified pneumonia, and blinded the auscultators to the clinical history. It wasn’t pretty – the sensitivity of the 3 examiners ranged from 47% to 69%. Specificity wasn’t much better.

This all comports with a JAMA metaanalysis from 1997 that concluded that “no individual clinical findings, or combinations of findings, that can rule in the diagnosis of pneumonia.” Specifically, while one study was wildly bullish on egophony, all the auscultation signs were of variable sensitivity, and generally low yield.

(BTW, CHF is even worse for the proponents of ‘scopes. While crackles modestly raise the likelihood of CHF, and wheezes modestly decrease such likelihood, there is some serious overlap! Between 1/5 to 1/3 of patients manifest wheezing with acute CHF. By the same token, wheezing is surprisingly unhelpful in diagnosing or excluding obstructive lung disease.)

Compare this to using ultrasound

While some authors have stated that “highly-skilled sonographers“ are required to diagnose pneumonia with ultrasound, a recent study required pediatric EM doctors to undergo only 1 hour of training. Despite this limited education, the sensitivity and specificity of US for CXR-proven consolidation was 86% and 89%. However, another study, using CT scan as the gold standard, found US to be far more sensitive than CXR. A raft of other studies have come out in the last few years (do they ultrasound anything but lungs in Italy?), backing up these results.

So, why are you carrying that MRSA biofilm-vehicle around the same neck your kids touch?

If you really need some jewelry to identify you as a doc, you can get a stethoscope earring. Cute as heck, and unlikely to get covered in MRSA, or give you a black eye.