community acquired pneumonia (CAP)

Last reviewed 10/2022

Community acquired pneumonia is a common disease with a reducing incidence. It usually occurs in children or the elderly, or in people with an underlying pathology.

This type of pneumonia is often a complication of viral respiratory disease such as influenza.

It is particularly common in winter in countries with temperate climates.

Eighty percent of community acquired pneumonia is pneumococcal pneumonia.

Other causes of community acquired pneumonias include haemophilus influenzae, staphylococcal aureus, atypical pneumonias (e.g. due to mycoplasma pneumoniae), mycobacterium tuberculosis, and viruses.

Every year between 0.5% and 1% of adults in the UK will have community-acquired pneumonia

• diagnosed in 5-12% of adults who present to GPs with symptoms of lower respiratory tract infection, and 22-42% of these are admitted to hospital, where the mortality rate is between 5% and 14%
• between 1.2% and 10% of adults admitted to hospital with community-acquired pneumonia are managed in an intensive care unit, and for these patients the risk of dying is more than 30%
• more than half of pneumonia-related deaths occur in people older than 84 years

Key messages from the BTS guidelines on management of community acquired pneumonia include (1,2):

• clinical judgement, supported by the CRB65 score, should be used to decide whether to treat patients at home or in hospital
• when deciding on home treatment, the patient's social circumstances and wishes must be taken into account in all instances
• patients in the community should be reviewed after 48 hours, or earlier if clinically indicated
• patients with suspected CAP should be advised to rest, drink plenty of fluids and not to smoke
• pleuritic pain, in the context of CAP, should be managed with simple analgesia such as paracetamol
• pulse oximetry should be available to GPs and others responsible for assessing patients in the out-of-hours setting, for the assessment of severity and oxygen requirement in patients with CAP and other acute respiratory illnesses
• amoxicillin 500mg three times daily is the preferred antibiotic, with doxycycline or clarithromycin as alternatives, for example in those patients hypersensitive to penicillins
• microbiological investigations are not recommended routinely but may be appropriate in certain circumstances. For example, sputum examination should be considered for patients who do not respond to empirical antibiotic therapy
• in patients with suspected severe, life-threatening CAP referred to hospital, GPs should administer antibiotics in the community before transfer; benzylpenicillin 1.2g intravenously or amoxicillin 1g orally are preferred.

Reference:

• 1) MeReC Monthly; January 2009: Number 22.
• 2) British Thoracic Society. Guidelines for the management of community acquired pneumonia in adults: update 2009. Thorax 2009;64 (Suppl III):1-55.
• 3) NICE (December 2014).Pneumonia- Diagnosis and management of community- and hospital-acquired pneumonia in adults