Inappropriate diagnosis of pneumonia in adult patients common, study finds

Older man in hospital bed

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A study of hospitals in Michigan found that one in eight patients treated for pneumonia were inappropriately diagnosed, researchers reported today in JAMA Internal Medicine.

The cohort study of more than 17,000 hospitalized adults treated for pneumonia at 48 Michigan hospitals found that 12% were inappropriately diagnosed. Older patients, those with dementia, and patients presenting with altered mental status were the most likely to be improperly diagnosed.

In addition, nearly 88% of patients with an inappropriate pneumonia diagnosis received a full course of antibiotics, which was associated with an increased risk of antibiotic-associated adverse events and can contribute to antibiotic resistance.

The authors of the study say the findings have important clinical and policy implications.

Weighing potential harms

Led by researchers with the Veterans Affairs (VA) Ann Arbor Healthcare System and the University of Michigan Medical School, the study analyzed data collected from July 2017 through March 2020 from the Michigan Hospital Medicine Safety Consortium (HMS), a statewide quality initiative that aims to improve care for hospitalized patients at risk of adverse events. Community-acquired pneumonia (CAP) has been a focus of HMS, because it's the most common cause of medical hospitalization in the United States and a frequent source of antibiotic overuse.

The researchers wanted to explore how many pneumonia patients are wrongly diagnosed, because little is known about how frequently inappropriate diagnosis occurs and what the risk factors are. The practice may also cause harm.

"Inappropriate diagnosis of CAP may harm patients through delayed recognition and treatment of acute (eg, exacerbations of congestive heart failure), chronic (eg, pulmonary cancer), or novel diagnoses (eg, pulmonary cancer) and may lead to unnecessary antibiotic use, adverse effects, and antibiotic resistance," they wrote.

To determine which patients treated for pneumonia during the study period were inappropriately diagnosed, the researchers used a definition endorsed by the National Quality Forum, which defines inappropriate diagnosis of CAP as any antibiotic treatment for CAP in a patient with two or fewer signs or symptoms of pneumonia or who lacks radiographic findings consistent with pneumonia. They also looked at risk factors for inappropriate diagnosis, outcomes, and adverse events.

Higher incidence in older, dementia patients

Of the 17,290 patients treated for CAP at the 48 hospitals, 2,079 (12.0%) met the criteria for inappropriate diagnosis (media age, 71.8 years; 50.3% female). Of these patients, 1,821 (87.6%) received full antibiotic courses for a median of 7 days. Nearly three quarters (73.6%) of inappropriately diagnosed patients lacked radiographic findings, and 24.4% had two or fewer symptoms. Thirty of the 48 hospitals inappropriately diagnosed 10% or more of patients with CAP.

Compared with patients who had CAP, inappropriately diagnosed patients were older (adjusted odds ratio [AOR], 1.08; 95% confidence interval [CI], 1.05 to 1.11) and more likely to have dementia (AOR, 1.79; 95% CI, 1.55 to 2.08) or present with altered mental status (AOR, 1.75; 95% CI, 1.39 to 2.19).

When the researchers compared outcomes among inappropriately diagnosed patients who received full (more than 3 days) versus brief (3 days or less) duration of antibiotic treatment, they found no difference for the 30-day composite outcome of mortality, readmission, emergency department visit, Clostridioides difficile infection, and antibiotic-associated adverse events (25.8% vs 25.6%; AOR, 1.00; 95% CI, 0.78 to 1.29). But full duration of antibiotic treatment was associated with a much higher rate of antibiotic-associated adverse events (2.1% vs 0.4%; AOR, 7.23; 95% CI, 1.18 to 44.35).

A balancing act

The study authors say there are several reasons why physicians may inappropriately diagnose pneumonia. For one, they could be influenced by the fact that it's a very common condition, particularly in older adults.

But it also can be difficult to diagnose, because the symptoms are non-specific and may overlap with other cardiopulmonary diseases. And because CAP is associated with poor outcomes in older patients, physicians might prefer overtreatment to missing a CAP diagnosis.

In addition, CAP is one of several conditions, including urinary tract infections, that tend to get overdiagnosed in older patients, particularly those with cognitive impairments who have difficulty communicating.

While brief empiric antibiotic treatment in older patients at risk of poor outcomes from CAP may be warranted, the authors note, guidelines generally recommend reconsidering, de-escalating, or stopping antibiotics within 48 to 72 hours once infection has been ruled out. Yet the study found that patients with presumed CAP received a full antibiotic course, which in turn was linked with adverse events.

"Thus, balancing harms of underdiagnosis and overdiagnosis of CAP remains essential," they concluded.

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