Chapter 10-6: Differential Diagnosis of Acute Cough and Congestion

1. Common cold

2. Sinusitis

3. Bronchitis

4. Influenza

5. Pertussis

6. Pneumonia

   1. Community-acquired pneumonia (CAP)

   2. Hospital-acquired pneumonia

   3. Aspiration pneumonia

   4. Tuberculosis (TB)

   5. Opportunistic (eg, Pneumocystis jirovecii pneumonia [PJP])

The approach to such patients focuses on 2 pivotal questions. First, does the patient have symptoms, signs, or risk factors for pneumonia that warrant a chest radiograph or other evaluation? Second, in patients with pneumonia, is it a CAP vs. another type of pneumonia (such as PJP, aspiration pneumonia, TB, etc.) that requires additional diagnostic evaluation and/or treatment?

1. The diagnosis of pneumonia is usually based on clinical findings (cough, fever, crackles), accompanied by infiltrate on chest film. Microbiologic confirmation is usually unnecessary.

2. When evaluating a patient who has acute respiratory symptoms it is imperative to determine who is likely to have pneumonia and therefore needs a radiograph to evaluate their symptoms.

3. Prevalence of symptoms in patients with pneumonia

   1. Cough, 96%

   2. Fever, 81% but 53% in the elderly

      Elderly patients with pneumonia often do not have a fever. Clinicians should have a low threshold for obtaining a chest radiograph in elderly patients with a cough.

   3. Dyspnea, 46–66%

   4. Pleuritic chest pain, 37–50%

   5. Chills, 59%

   6. Headache, 58%

4. Physical exam

   1. No single finding is very sensitive. Therefore, the absence of any single finding does not rule out pneumonia (Table 10-1).

      1. Neither a normal lung exam nor the absence of fever rule out pneumonia (LR–, 0.6 and 0.8, respectively).

         A normal lung exam does not rule out pneumonia.

      2. Normal vital signs make pneumonia less likely (LR–, 0.18).

      3. The combination of normal vital signs and normal chest exam make pneumonia highly unlikely (sensitivity, 95%; LR–, 0.09).

         Normal vital signs and a normal lung exam make pneumonia unlikely.

   2. Egophony is fairly specific and significantly increases the likelihood of pneumonia when present (LR+, 8.6).

In summary, there are signs and symptoms that suggest pneumonia because they are unusual in upper respiratory tract infections or bronchitis. These include dyspnea, high fever (with the exception of influenza [see below]), altered mental status, hypoxia, hypotension, and abnormal findings on chest examination (dullness to percussion, crackles, decreased breath sounds, bronchophony, or egophony). Any patient with such symptoms or signs requires a chest radiograph to rule out pneumonia. A chest radiograph should also be strongly considered in patients at increased risk for poor outcomes, including immunocompromised patients, elderly patients, patients with heart failure, chronic kidney disease, or chronic obstructive pulmonary disease (COPD) (in whom abnormal lung findings are also more difficult to appreciate). On the other hand, patients with normal vital signs, a normal lung exam and who are not at risk for poor outcomes do not normally need a chest radiograph. Figure 10-1 shows a diagnostic algorithm illustrating the initial approach to patients with cough and congestion.

In patients discovered to have pneumonia, the next pivotal step is to determine the likely etiologic pathogen(s) to ensure patients receive appropriate therapy. While most patients seen in the community with pneumonia have community-acquired pneumonia (due ...