Clinical: Community-Acquired Pneumonia

Community-Acquired Pneumonia is an infection of the lungs that occurs outside the hospital setting.

Other Names
Outpatient Pneumonia

Signs and Symptoms
There are no combination of symptoms and physical examination findings that can rule out or assure the diagnosis of pneumonia. Hence, if diagnosis certainty is required for the management of the patient a chest X-ray must be obtained.

The diagnosis algorithm of Diehr could help to orientate the diagnosis. It is built adding the following signs and symptoms punctuations:


 * Rhinorreha -2 points
 * Sore throat -1 point
 * Night sweats +1 point
 * Myalgias +1 point
 * Sputum all day +1 point
 * Respiratory rate >25 breaths/min +2 points
 * Temperature >=37.8ºC(100ºF) +2 points

A threshold of +1 (>+1 meaning a diagnosis of pneumonia) yields an LR+ of 5.0 and a LR- of 0.47, based on the original study data.

Causes
We will focus in this article in the bacterial (non chemical, inmunological or virical) causes of pneumonia and specifically in the epidemiological patterns of community adquired pneumonia (CAP). Streptococcus pneumoniae is the most prevalent etiologic agent (8%-46%). Other agents are Haemophilus influenzae (2%-11%) and Moraxella catarrhalis (2%). A group of atypical pathogens, including Chlamydia pneumoniae (6%-15%), Legionella pneumophila (1%-16%), and Mycoplasma pneumoniae, are now being reported more frequently than in the past.