Community acquired pneumoniaBMJ 2010; 341 doi: https://doi.org/10.1136/bmj.c2916 (Published 07 July 2010) Cite this as: BMJ 2010;341:c2916
- L Mandell, professor of medicine
- 1McMaster University, Division of Infectious Diseases, Henderson Hospital, 711 Concession Street, Hamilton, ON, Canada L8V 1C3
Community acquired pneumonia is an important cause of morbidity and mortality, yet it is often misdiagnosed and improperly treated. Guidelines have been produced by several societies, and these have helped to organise the approach to this disease; highlighted areas that need further research; and reduced length of stay, mortality, and costs in patients admitted to hospital.1 2 3 4 5
Recently a summary of the British Thoracic Society (BTS) guidelines for community acquired pneumonia was published that focuses on management in primary care.3 6 The guidelines are a manageable length for general practitioners and have important educational and quality assurance functions.
Some of the BTS recommendations however, differ from those of the Infectious Diseases Society of America (IDSA) and American Thoracic Society (ATS) guidelines. Although the practice of medicine and the prevalence of certain pathogens may differ between the United Kingdom and United States, certain problems are common on both sides of the Atlantic. The diagnosis of pneumonia is one of them.
There are two key factors in the diagnosis of community acquired pneumonia. The first is whether the patient actually has pneumonia and the second is identification of the pathogen responsible.
Several infectious and non-infectious entities can be confused with pneumonia. The BTS summary statement claims that the typical patient history of cough, fever, and dyspnoea with chest pain and lung crackles on examination cannot reliably discriminate community acquired pneumonia from other acute lower respiratory tract infections. They also state that various prediction rules have generally “shown the need for confirmatory radiographic evidence.” Despite this, there seems to be undue reliance on the clinical diagnosis of community acquired pneumonia and a routine chest radiograph is not recommended. It is suggested instead that a chest radiograph may be done if the diagnosis is in doubt. This is a circular argument because with the use of clinical criteria alone the diagnosis of pneumonia is often in doubt, especially if the doctor is trying to assess the patient within the six to 12 minute time slot referred to in the summary. Rapid access to chest radiography may be limited in the UK just as it is in many North American cities and towns, but this does not mean that doctors should not strive for a correct diagnosis whenever possible, because this has an effect on the proper use of antimicrobials and treatment of the correct disease entity. It could be argued that if the time available to assess the patient is limited the chest radiograph becomes even more important.
Determining the pathogen can be just as difficult and frustrating. Ideally the micro-organism should be identified so that specific antimicrobial treatment can be given, misuse of antibiotics and emergence of resistance reduced, and important epidemiological information collected. However, the problem is that most sputum samples are of poor quality, and elderly patients may have difficulty producing an expectorated sample. This problem may be compounded by patients taking an oral antibiotic that they have at home before seeking medical care. A single dose of a drug to which the organism is susceptible can result in failure to isolate it even from a properly collected sputum sample from a patient with pneumococcal pneumonia.
The guideline’s suggestion that serological investigations may be helpful with Mycoplasma pneumoniae infections must be carefully interpreted. Although complement fixing antibodies for this micro-organism can be quite specific they are not detectable early enough to be used in treatment decisions. Their main role is to provide epidemiological data.
The decision regarding severity assessment and whether to treat the patient in the community or in hospital requires a reliable prediction rule. This decision determines the extent of diagnostic investigation, the spectrum and route of administration of antibiotics, and treatment costs. Prediction rules that are overly sensitive or not specific enough are unhelpful.
Several prediction rules exist, such as the pneumonia severity index and the various CURB-type scores (CURB, CURB-65, CRB, and CRB-65). CURB is an acronym for confusion, urea, respiratory rate, and blood pressure, and 65 refers to the patient’s age in years.7 8 9 The pneumonia severity index involves 20 variables, is heavily age weighted, and may underestimate severity in younger patients. The CRB-65 prediction rule recommended by the BTS is much easier to apply and is well suited to decide where to treat the patient.9 10
One of the most contentious areas is treatment of patients with community acquired pneumonia on an outpatient basis. The Canadian and IDSA-ATS guidelines recommend initial empirical coverage for bacterial pathogens such as Streptococcus pneumoniae and Haemophilus influenzae as well as atypical pathogens such as M pneumoniae and Chlamydophila pneumoniae.1 2 The BTS guidelines recommend amoxicillin as the preferred agent because they consider the atypical agents to be relatively uncommon and M pneumoniae to have a low mortality rate and affect mostly younger patients.3
It is understandable that different countries have different recommendations for treating community acquired pneumonia, particularly if the decisions are based on local epidemiological data. However, there seems to be an inconsistency in the BTS guidelines which is reflected in the summary. Amoxicillin or co-amoxiclav plus clarithromycin are recommended for patients with community acquired pneumonia of moderate or high severity, respectively, who require hospital admission.3 They also recommend, however, that for potentially life threatening community acquired pneumonia, general practitioners should give antibiotics in the community, preferably 1.2 g penicillin G intravenously or 1 g amoxicillin orally. If the infection is truly considered to be life threatening why should the general practitioner give only penicillin or amoxicillin and not provide additional coverage with a macrolide? Such coverage would be consistent with the recommendation for treatment of these patients admitted to hospital.
Cite this as: BMJ 2010;341:c2916
Competing interests: The author has completed the Unified Competing Interest form (available on request from the corresponding author) and declares: (1) No financial support for the submitted work from anyone other than his employer; (2) He has received consultancy fees from Cempra, Novexel and Cerexa; payment for expert testimony from Ortho-McNeil; and travel expenses from Novexel and Cerexa; (3) No spouse, partner, or children with relationships with commercial entities that might have an interest in the submitted work; (4) He was co-chair of the IDSA/ATS CAP guideline group.
Provenance and peer review: Commissioned; not externally peer reviewed.