lists the other diagnoses that should be considered when patients present with focal chest signs and increasing shortness of breath. A chest x ray is crucial to making the diagnosis of pneumonia. New chest signs on examination are helpful but not specific. One clinical study conducted in primary care in the United Kingdom showed that only 40% of patients with new lower respiratory tract symptoms and focal chest signs had radiological evidence of pneumonia.4
Differential diagnosis in community acquired pneumonia
About 40% of patients have a pleural effusion, but the amount of fluid is usually small.1
A microbiological diagnosis can be made on routine microbiological tests in only about 15% of inpatients; this percentage is even lower in patients with mild or moderate pneumonia and no comorbid illnesses.5
The following tests are recommended for patients admitted with non-severe community acquired pneumonia:
- Full blood count
- Urea and electrolytes
- Liver function tests
- Sputum culture
- Chest x ray
- Blood cultures.
In patients with severe pneumonia, tests for atypical pathogens (Mycoplasma pneumoniae, Chlamydia sp, Coxiella burnetii, Legionella sp) and viruses should also be carried out. These are:
- Legionella urinary antigen test
- Direct immunofluorescence on respiratory samples
- Serological tests on acute and convalescent serum samples.
Testing for pneumococcal urinary antigen is also recommended in severe pneumonia.