Community Acquired Pneumonia (Adult) – Diagnosis
Infections, Respiratory
Context
- Community Acquired Pneumonia (CAP) = no prior hospitalization in past 14 days or onset <48 hours since admission.
- In immunocompetent adults:
- Typical bacteria: Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Staphylococcus aureus.
- Atypical bacteria: Mycoplasma pneumoniae, Chlamydophila pneumoniae, Legionella species.
- Viral: Influenza A/B, respiratory syncytial virus, adenovirus, parainfluenza, coronavirus (see Covid 19: Clinicians).
Diagnostic Process
- Clinical Manifestations
- Dyspnea, tachypnea, cough +/- sputum changes, pleuritic pain.
- Fever and/or rigors, malaise, muscle aches and confusion.
- Abnormal lung exam (eg. crackles on auscultation or dullness to percussion).
- Investigations
- Chest radiographs:
- New opacity, not suggestive of another diagnosis, confirms CAP.
- FAST Ultrasound: B lines, hepatization.
- Arterial blood gases: Consider if SpO2 <94%, receiving oxygen or otherwise severe CAP.
- Chest radiographs:
- Severity Assessment
- A prognosis clinical prediction rule, in addition to clinical judgement, is recommended. Two are commonly used:
- Pneumonia Severity Index (PSI)
- Useful tool which provides an excellent risk stratification. For most patients however, the CURB-65 is easier to use and requires fewer inputs.
- CURB-65
- Confusion, BUN > 7 mmol/L, RR > 30, SBP < 90 or DBP < 60 mmHg, Age > 65
- Pathogen Identification
- MRSA/Pseudomonas Risk:
- Locally validated risk factors are best.
- Risk factors include:
- prior infection with MRSA or Pseudomonas or,
- hospitalization involving IV antibiotics within the last 90 days.
- Sputum Testing:
- Sputum Culture for patients admitted to hospital who can produce a sputum sample.
- Sputum Gram Stain if severe CAP or if MRSA or Pseudomonas are suspected.
- Obtain before starting antibiotics if possible.
- Blood Culture:
- Recommendations based on low quality evidence suggest only obtaining for severe CAP, or if MRSA or Pseudomonas are suspected.
- Obtain before starting antibiotics if possible.
- Urinary Antigen Testing:
- pneumoniae – Consider for severe CAP.
- Legionella – Obtain if there are risk factors (eg. travel) or ongoing outbreak. Consider for severe CAP.
- Tests for Atypical Bacteria and Viruses (eg. Nasopharyngeal swab):
- During flu season or an outbreak test for responsible pathogens.
- MRSA/Pseudomonas Risk:
- Differential Diagnosis
- Heart Failure.
- COPD/Asthma exacerbation.
- Aspiration pneumonitis.
- Pulmonary embolism.
- Acute Coronary Syndrome.
- Pneumothorax.
Quality Of Evidence?
High
We are highly confident that the true effect lies close to that of the estimate of the effect. There is a wide range of studies included in the analyses with no major limitations, there is little variation between studies, and the summary estimate has a narrow confidence interval.
Moderate
We consider that the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. There are only a few studies and some have limitations but not major flaws, there are some variations between studies, or the confidence interval of the summary estimate is wide.
Low
When the true effect may be substantially different from the estimate of the effect. The studies have major flaws, there is important variations between studies, of the confidence interval of the summary estimate is very wide.
Justification
Evidence relies on American Thoracic Society updated guidelines on CAP from 2019 as well as other sources all produced in the last few years.
Related Information
Reference List
Relevant Resources
RESOURCE AUTHOR(S)
DISCLAIMER
The purpose of this document is to provide health care professionals with key facts and recommendations for the diagnosis and treatment of patients in the emergency department. This summary was produced by Emergency Care BC (formerly the BC Emergency Medicine Network) and uses the best available knowledge at the time of publication. However, healthcare professionals should continue to use their own judgment and take into consideration context, resources and other relevant factors. Emergency Care BC is not liable for any damages, claims, liabilities, costs or obligations arising from the use of this document including loss or damages arising from any claims made by a third party. Emergency Care BC also assumes no responsibility or liability for changes made to this document without its consent.
Last Updated Aug 25, 2020
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