The overdiagnosis of pneumonia

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Pneumonia was once considered the “old man’s friend,” but in the modern world, has it become the physician’s?

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The definition of pneumonia has increasingly been stretched, and physicians occasionally make the diagnosis without canonical signs or symptoms, or even with negative chest radiography. The hallmark of overdiagnosis is identifying illness for which treatment is not needed or is not helpful, and some cases of pneumonia likely fit this description. Empirical evidence over the last 3 decades shows a sustained increase in the diagnosis of pneumonia, but little evidence of a decrease in the rates of pneumonia morbidity and mortality. The central problem with pneumonia is one common to many diagnoses, such as pulmonary embolism, coronary artery disease, and infectious conditions—diagnostic criteria remain divorced from outcomes data. Linking the two has the potential to improve the evidence base of medicine.

Like many long-recognized diagnoses, pneumonia lacks a standardized definition. Most physicians believe that although fever, cough, sputum production, dyspnea, and pleurisy are hallmark symptoms, confirmatory chest radiography is needed to cement the diagnosis.1 But what if a patient has only a fever, cough, and infiltrate? What if the infiltrate is not visible on radiography, but only on computed tomography (CT)? And what if the patient has a cough but is afebrile and has nonspecific findings on CT?


In current clinical practice, any or all of the above cases are called pneumonia. The pneumonia label, once applied, justifies the use of antibiotics, which patients or physicians may overtly desire. One prospective observational study of six hospitals found that 21% of patients admitted with pneumonia and 43% of those treated as outpatients had negative chest radiographs.2 Empirical evidence suggests that the incidence of these “soft” diagnoses may be growing in number.

In the United States, hospitalizations with discharge codes listing pneumonia increased 20% from the late 1980s to the early 2000s.3 The rates of hospitalization for the 10 other most frequent causes of admission did not change significantly over this same period, suggesting a selective increase in hospital admissions for pneumonia.

This focus on pneumonia would be justified if it led to a proportionate benefit for pneumonia outcomes. However, in the same data set, the risk of death from pneumonia did not improve more than that from the other 10 common conditions—all improved similarly—and the rate of discharge from the hospital to a long-term care facility was unchanged. We are hospitalizing more patients with pneumonia, but this has not improved outcomes beyond global trends in mortality.

Data from England suggest that overdiagnosis may be a worldwide phenomenon. Between 1997 and 2005, hospitalization rates in England for pneumonia, adjusted for age, increased 34% from 1.48 to 1.98 per 1,000 persons.4 The 30-day in-hospital death rate for pneumonia remained about the same over this period. In the absence of a paradigm-shifting technology, one that would alter hospitalization practices, or an environmental cause of increased incidence—and with pneumonia there has been neither—the most likely explanation for these documented trends is that hospitals are admitting patients with pneumonia that is less severe.

Finally, data from the 2000s that at first seemed to reverse the trend of increasing hospitalizations for pneumonia have been reanalyzed to account for alternative coding.5 For instance, a pneumonia admission may be coded with respiratory failure as the primary diagnosis and pneumonia as the secondary diagnosis. Examining data from large populations from 2002 to 2009, and correcting as such, shows that the incidence of pneumonia has reached a plateau or has declined only slightly from the elevated rates of the early 2000s. The death rate remains unchanged.

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