Section 1: Epidemiology and aetiology
This review considers community-acquired pneumonia (CAP) in adults, excluding non-pneumonic lower respiratory tract infection (LRTI), exacerbation of chronic lung disease (such as COPD), pneumonia in the immunocompromised, and pneumonia as a preterminal event.
Every year 0.5-1% of the adult population will experience CAP, with those aged over 60 years being most affected.1 Of adults presenting to primary care with symptoms of an LRTI, 5-12% will have CAP,1,2 of whom 22-42% will be admitted to hospital.1,3
Streptococcus pneumoniae (Pneumococcus) is the most commonly identified pathogen, accounting for 20-60% of CAP cases in the UK, and two-thirds of bacteraemic cases. About 10% of cases of CAP are due to viruses, and about 10% have more than one pathogen. Haemophilus influenzae and Moraxella catarrhalis are more common in those with underlying lung disease such as COPD, although Strep pneumoniae remains the most common cause of CAP in this group.
The term ‘atypical pneumonia’ is non-specific and often unhelpful. It may refer to an atypical presentation (such as with headaches, rashes or fatigue, rather than predominant respiratory symptoms), or less common pathogens (the definition of which has varied from any pathogen other than Strep pneumoniae, to pathogens that are not sensitive to penicillin, to specific intracellular pathogens such as Legionella, Mycoplasma and Chlamydia species).4 Although some features are more common with specific pathogens (such as recent foreign travel in those with Legionella), it is not possible to accurately predict the causative organism from clinical features alone.
The concept of healthcare-associated pneumonia (HCAP) has emerged in recent years, referring to patients who reside in long-term care facilities. In other countries, such as the US, there is evidence that multiresistant pathogens are more likely to cause pneumonia in these patients, but in the UK, this does not currently appear to be the case.5
Section 2: Making the diagnosis
CAP is differentiated from bronchitis by consolidation of the lung parenchyma. In secondary care, the diagnosis of CAP requires a combination of symptoms and signs of an LRTI, together with new infiltrates seen on a chest-X-ray, with no alternative explanation. In primary care, where chest X-rays are not usually immediately available, a clinical diagnosis of CAP is made based on the following criteria:6
- Symptoms of an LRTI (cough and at least one other lower respiratory tract symptom)
- New focal chest signs on examination
- At least one systemic feature (fevers, sweats, rigors and/or a temperature of ≥38oC).
However, of patients with new focal chest signs treated with antibiotics in the community, only about 40% will have radiological evidence of CAP.1
A chest X-ray is only indicated in the community if the diagnosis is in doubt and an X-ray is likely to alter acute management, if progress following treatment is unsatisfactory, or if there is a high risk of underlying lung pathology, such as lung cancer.6
Identifying which patients with LRTI symptoms require antibiotics can be difficult. Patients with a clinical diagnosis of pneumonia, and those without pneumonia but at high risk of complications (such as those who are systemically unwell, or those with significant comorbidities) require antibiotics.7 Most other patients will not benefit from antibiotics.8
With rising antibiotic resistance and a lack of new antibiotics in development, rationalising the use of antibiotics is increasingly important. As such, there has been much research in recent years into point-of-care testing to identify which patients will benefit from antibiotics.
Procalcitonin is a hormone whose levels rise in the presence of inflammation, particularly due to pathogenic bacteria. Procalcitonin and CRP are both available as quick point-of-care tests and could practicably be used in primary care.9
Although there is insufficient evidence to recommend either test to differentiate non-pneumonic LRTI from CAP, they can be useful when applied to patients with LRTI when pneumonia is not suspected and the decision to prescribe antibiotics is uncertain.
In this population, both tests can significantly reduce the use of antibiotics without causing harm.9 Point-of-care CRP testing costs less than procalcitonin, and consideration of point-of-care CRP testing has recently been recommended by NICE as a cost-effective strategy to reduce antibiotic prescribing.9
Section 3: Managing the condition
When a clinical diagnosis of CAP has been made in primary care, a key decision is whether to refer the patient for hospital assessment. CRB65 is a tool that can help determine mortality risk (see table 1).9,10
Patients with a score of zero are at low risk of mortality and can usually be managed safely in the community.
However, it is important to use clinical judgment in conjunction with CRB65 when making decisions on whether to refer to hospital. Some patients with a score of zero can be still be severely unwell and require admission. Some at intermediate risk but systemically well can be managed in the community, and some at high risk of death may be inappropriate for hospital referral (for example, those with life-limiting comorbidities in whom pneumonia may be a preterminal event, and palliation in the community in the event of deterioration is deemed appropriate).
|Table 1: CRB65 score for mortality risk assessment in primary care|
|C Confusion (new disorientation or abbreviated mental test score 8 or less)|
|R Respiratory rate 30/min or more|
|B Systolic BP less than 90mmHg, or diastolic BP 60mmHg or less|
|65 Age 65 years or more|
|Score one point for each|
|0: low risk (<1% mortality) – consider home-based care|
|Consider hospital assessment for all other patients, particularly those with a CRB65 score of 2 or more|
|1-2: intermediate risk (1-10% mortality)|
|3-4: high risk (more than 10% mortality)|
|Patients with CAP should be stratified by disease severity (low, moderate or high). This will usually correspond to their mortality risk.|
Microbiological tests are not usually indicated in low-severity CAP, which accounts for the majority of cases managed in primary care. An important exception is patients with chronic lung diseases such as COPD, bronchiectasis or cystic fibrosis, who are more likely to become colonised with pathogens such as Pseudomonas, which do not respond to the standard antibiotic treatments used in CAP.
A sputum sample sent for culture can be very helpful in these circumstances, because antibiotic treatment may need to be modified if they fail to respond to empirical therapy.
Amoxicillin remains the empirical treatment of choice in patients with low-severity CAP, with clarithromycin or doxycycline as alternatives, particularly for patients allergic to penicillin.
The standard dose of amoxicillin should be 500mg three times daily – lower doses than this are not indicated in CAP. Dual antibiotic therapy (usually a beta-lactam with a macrolide antibiotic) should not routinely be given in primary care, and is reserved for patients with higher-severity CAP.
Approximately 5% of Strep pneumoniae cases are resistant to amoxicillin in the UK, but in a low-severity population, the risks of widespread use of broad-spectrum antibiotics outweigh the benefits.
A five-day course of antibiotics is now recommended in low-severity CAP; a change from the previous guidance of seven days.6,9 Symptoms should start to improve within three days of starting treatment and in those who do not begin to improve within three days, extending the course is a possible management strategy, although consideration of alternative diagnoses (such as heart failure) and assessment for complications of CAP (such as parapneumonic pleural effusion) are also important.
All patients with CAP who smoke should be given smoking cessation advice.
Section 4: Prognosis
The mortality rate in CAP varies by disease severity, from less than 1% in patients with low-severity CAP managed in the community, to approximately 20% of all patients with CAP admitted to hospital, to up to 50% of patients managed in intensive care units.6,11,12
Antibiotics probably lead to microbiological clearance of pathogens in CAP early in the disease, but it takes longer for symptoms, clinical signs and radiological changes on X-ray to resolve.
Symptoms should steadily improve over time, but most patients will continue to have symptoms such as productive cough or fatigue beyond the end of their antibiotic course (see figure 1).9 Many patients receive unnecessary further courses of antibiotics because of lingering symptoms, which simply represent the natural resolution of their illness. Informing patients of the natural history of the symptoms of CAP at the time of diagnosis may be helpful in reducing this practice.
Figure 1 Resolution of symptoms in patients with CAP
Source: Adapted from figures in NICE CG191
Section 5: Case study
A 72-year-old man has a history of controlled hypertension but is otherwise fit and well. He presents with a three-day history of breathlessness, cough productive of green sputum, and fever, which started following a coryzal illness. He feels ‘washed out’ but was still able to do his shopping at the supermarket that morning before his appointment. He lives with his wife, has never smoked and has no drug allergies. His only medication is amlodipine 5mg once daily.
On clinical examination, he looks reasonably well, is alert and orientated, and has a temperature of 38oC, heart rate of 90bpm and respiratory rate of 20/minute. Oxygen saturations are 97% on room air and BP is 110/70mmHg. Examination of the chest reveals coarse crackles at the right lung base with no wheeze. In view of the combination of symptoms and signs, you make a clinical diagnosis of CAP.
You calculate the patient’s CRB65 score and he scores 1 for his age. As such, you consider whether he requires hospital assessment. He is reasonably well, with little in the way of comorbidities, and he is not socially isolated. You consider him suitable for home-based treatment and prescribe amoxicillin 500mg three times daily for five days.
You explain that he should begin to improve within a few days, but it may take longer for his symptoms to resolve, and he should seek further medical attention if he fails to improve or develops new or worsening symptoms.
The patient attends the surgery again one week later. His fever has resolved and his sputum is now white, but he continues to have a productive cough. He has no chest pain and is otherwise well. Examination of the chest reveals crackles as before, but no signs suggestive of a pleural effusion.
You explain that the cough associated with pneumonia can take several weeks to improve, and you are happy with his progress. You advise him to make a further appointment if his symptoms deteriorate, or if things have not fully settled within a few weeks.
Section 6: Evidence base
- NICE. Pneumonia - Diagnosis and management of community- and hospital-acquired pneumonia in adults. CG191. London, NICE, December 2014
- Lim WS, Baudouin SV, George RC et al. BTS guidelines for the management of community acquired pneumonia in adults: update 2009. Thorax 2009; 64 Suppl 3: iii1-55
The BTS guidelines predate the NICE guidelines, but have a wider scope; many of the recommendations that are not covered by the NICE guidelines remain applicable. An annotated version of the BTS guidelines incorporating the NICE recommendations is available at: https://www.brit-thoracic.org.uk/guidelines-and-quality-standards/community-acquired-pneumonia-in-adults-guideline/annotated-bts-guideline-for-the-management-of-cap-in-adults-2015
Lim WS, van der Eerden MM, Laing R et al. Defining community acquired pneumonia severity on presentation to hospital: an international derivation and validation study. Thorax 2003; 58(5): 377-82
- RCT on antibiotics in LRTI
Little P, Stuart B, Moore M et al. Amoxicillin for acute lower-respiratory-tract infection in primary care when pneumonia is not suspected: a 12-country, randomised, placebo-controlled trial. Lancet Infect Dis 2013; 13(2): 123-9
- Point-of-care CRP testing
NICE. Costing statement: Pneumonia – diagnosis and management of community- and hospital-acquired pneumonia in adults. Implementing the NICE guideline on pneumonia (CG191). London, NICE, December 2014. http://www.nice.org.uk/guidance/cg191/resources/cg191-pneumonia-costing-statement2
- Woodhead MA, Macfarlane JT, McCracken JS et al. Prospective study of the aetiology and outcome of pneumonia in the community. Lancet 1987; 1(8534): 6714
- Macfarlane JT, Colville A, Guion A et al. Prospective study of aetiology and outcome of adult lower-respiratory-tract infections in the community. Lancet 1993; 341(8844): 511-14
- Guest JF, Morris A. Community-acquired pneumonia: the annual cost to the National Health Service in the UK. Eur Respir J 1997; 10(7): 1530-4
- Marrie TJ, Costain N, La Scola B et al. The role of atypical pathogens in community-acquired pneumonia. Semin Respir Crit Care Med 2012; 33(3): 244-56
- Woodhead M. Pneumonia classification and healthcare-associated pneumonia: a new avenue or just a cul-de-sac? Thorax 2013; 68(11): 985-6
- Lim WS, Baudouin SV, George RC et al. BTS guidelines for the management of community acquired pneumonia in adults: update 2009. Thorax 2009; 64(Suppl 3): iii1-iii55
- NICE. Respiratory tract infections – antibiotic prescribing: Prescribing of antibiotics for self-limiting respiratory tract infections in adults and children in primary care. CG69. London, NICE, July 2008
- Little P, Stuart B, Moore M et al. Amoxicillin for acute lower-respiratory-tract infection in primary care when pneumonia is not suspected: a 12-country, randomised, placebo-controlled trial. Lancet Infect Dis 2013; 13(2): 123-9
- NICE. Pneumonia - Diagnosis and management of community- and hospital-acquired pneumonia in adults. CG191. London, NICE, December 2014
- Lim WS, van der Eerden MM, Laing R et al. Defining community acquired pneumonia severity on presentation to hospital: an international derivation and validation study. Thorax 2003; 58(5): 377-82
- Lim WS, Woodhead M. British Thoracic Society adult community acquired pneumonia audit 2009/10. Thorax 2011; 66(6): 548-9
- Lim WS, Rodrigo, Chamira. British Thoracic Society adult community acquired pneumonia audit 2012/13. Available from: https://www.brit-thoracic.org.uk/document-library/audit-and-quality-improvement/audit-reports/bts-adult-community-acquired-pneumonia-audit-report-201213/
Photo: Photostock Israel/Science Photo Library