Diagnosis
Pneumonia is typically diagnosed based on a combination of physical signs and a chest X-ray. However, the underlying cause can be difficult to confirm, as there is no definitive test able to distinguish between bacterial and non-bacterial origin. The World Health Organization has defined pneumonia in children clinically based on either a cough or difficulty breathing and a rapid respiratory rate, chest indrawing, or a decreased level of consciousness. A rapid respiratory rate is defined as greater than 60 breaths per minute in children under 2 months old, 50 breaths per minute in children 2 months to 1 year old, or greater than 40 breaths per minute in children 1 to 5 years old. In children, increased respiratory rate and lower chest indrawing are more sensitive than hearing chest crackles with a stethoscope.
In adults, investigations are generally not needed in mild cases: there is a very low risk of pneumonia if all vital signs and auscultation are normal. In persons requiring hospitalization, pulse oximetry, chest radiography and blood tests—including a complete blood count, serum electrolytes, C-reactive protein level and possibly liver function tests—are recommended. The diagnosis of influenza-like illness can be made based on the signs and symptoms; however, confirmation of an influenza infection requires testing. Thus, treatment is frequently based on the presence of influenza in the community or a rapid influenza test.
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