Blog | Monday, April 20, 2015

What is community acquired pneumonia?


Back in the 70s when I was training, we diagnosed pneumonia, and then tried to understand the likely bacteria causing the pneumonia. We knew the clinical presentations of various bacteria. We had a clear illness script for diagnosing pneumonia.

Then, if I recollect correctly, we had a new diagnosis: community-acquired pneumonia (CAP). Perhaps I am too old school, but CAP seems like a “cop out” diagnosis. Moreover, the label has become a crutch for hospital admission. Patients come to the emergency department with at least one symptom suggesting a chest X-ray. The CXR suggests an infiltrate and bingo we have an admission diagnosis.

I love admission diagnoses of CAP because these patients so often have something else. We can exercise our diagnostic muscles to either confirm or deny the original CAP diagnosis.

Why has this happened? I blame the Centers for Medicare and Medicaid Services (CMS)! In 2004, based on flawed data, CMS started reporting the percentage of pneumonia patients who received antibiotics within 4 hours of emergency department arrival. A wonderful series of articles then demolished this rule! Another performance measure bit the dust because the rule led to a significant increase in inappropriate antibiotic use.

But I believe the rule has a lingering impact. The rule told us that we cannot afford to miss pneumonia. Therefore, when in doubt we label patients with a pneumonia diagnosis. And too often we ignore the patient's history, focusing merely on a chest X-ray infiltrate.

Another factor comes into play, a very unfortunate factor. We seem to need a diagnosis to admit a patient, even when making the diagnosis is really the reason. I hope that sentence made sense. We no longer seem to admit patients for abnormal chest X-ray, diagnosis uncertain. Rather we place a label on the patient, one that induces the anchoring bias.

So I accuse the system that was trying to improve quality as actually causing diagnostic errors and inappropriate treatments. I accuse the system of fostering diagnostic delays. And I still do not know why we use the crutch diagnosis of CAP.

db is the nickname for Robert M. Centor, MD, FACP. db stands both for Dr. Bob and da boss. He is an academic general internist at the University of Alabama School of Medicine, and is the Regional Associate Dean for the Huntsville Regional Medical Campus of UASOM. He still makes inpatient rounds over 100 days each year. This post originally appeared at his blog, db's Medical Rants.