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Make the Diagnosis: Pneumonia, Adult, Community-Acquired

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Prior Probability

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Using cough as a requirement for considering pneumonia, the baseline probability of radiographic-proven pneumonia in patients with acute cough illness is about 5%.

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Population for Whom Community-Acquired Pneumonia Should Be Considered

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  • Patients with symptoms of acute respiratory illness, primarily cough.

  • Patients with comorbid illnesses, older patients, and those with immunocompromised status have a much higher risk for community-acquired pneumonia.

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Detecting the Likelihood of Community-Acquired Pneumonia

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Individual clinical symptoms or signs have low utility for identifying patients with pneumonia. Combinations of findings are required, including cough, fever, tachypnea, and abnormalities on auscultation (decreased breath sounds or crackles). The clinical decision that a patient has a low enough likelihood of pneumonia that a chest radiograph is not required lowers the probability of pneumonia to less than 5%. Rather than recommending one particular prediction model over the other for selecting patients who should have a chest radiograph, clinicians should use their own clinical judgment and the presence of increasing numbers of clinical signs and symptoms from the prediction models. The detection of pneumonia requires a chest radiograph, and the presence of appropriate findings on the chest radiographs is part of the case definition for pneumonia.

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Reference Standard Tests

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There is no practical reference standard test that allows correct categorization of the patient who has a pulmonary infection that will respond to antibiotics vs those that do not need antibiotics. The reference standard for pneumonia is the identification of a microbiologic pathogen from lung tissue. Because this is infrequently obtained, the pragmatic reference standard is the combination of clinical findings with appropriate abnormalities on a chest radiograph. A follow-up chest radiograph is often required to demonstrate improvement of the initial findings consistent with pneumonia or to identify findings not present on the first radiograph. The role of high-resolution CT for patients with a nondiagnostic initial chest radiograph result requires studies comparing the results to microbiologic outcomes.

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Original Article: Does This Adult Patient Have Community-Acquired Pneumonia?

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Clinical Scenario

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Does This Patient Have Pneumonia?
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A 53-year-old woman comes to your office with a cough of more than 1 week's duration. She was in excellent health until 7 days ago, when she developed a nonproductive cough, mild sore throat, and myalgia. She recalls no history of asthma or chronic obstructive pulmonary disease, and she does not smoke. Despite staying home from work for the last 2 days, she has noted increasing sputum production with her cough and worsening fatigue. She has felt warm but has not documented any fever or night sweats. On physical examination, her oral temperature is 38.3°C (101°F), her heart rate is 110/min, and auscultation of her chest reveals inspiratory crackles on the left side.

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Why ...

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