2019 CAP Guidelines Update

2019 CAP Guidelines Update
Kylea Larsen, PharmD, Coborn’s Pharmacy/Little Falls Family Medical Center

Background: The American Thoracic Society (ATS) and Infectious Diseases Society of America (IDSA) has released updated guidelines for the diagnosis and treatment of adults with community-acquired pneumonia (CAP). The 2019 ATS/IDSA CAP guidelines address 16 specific areas of CAP treatment and give recommendations using evidence-based rationale. Compared to the 2007 ATS/IDSA CAP guidelines, many recommendations are unchanged but there are some notable differences in the 2019 update. The major changes found in the 2019 guidelines include identification of patient populations for sputum and blood culture draws, utilization of the term “healthcare-associated pneumonia (HCAP),” treatment with macrolide monotherapy, and empiric therapy recommendations for severe CAP. 

Evidence: The 2019 ATS/IDSA CAP guidelines continue to recommend the use of sputum cultures and blood cultures in patients with severe disease managed in the hospital and recommend against the routine use of sputum cultures and blood cultures in the outpatient setting for adults with CAP. Additionally, the updated guidelines specify that sputum cultures and blood cultures should be obtained in patients who are empirically treated for Methicillin-resistant Staphylococcus aureus (MRSA) or Pseudomonas aeruginosa in the hospital due to specific risk factors for infection. These risk factors include previous infection with MRSA or P. aeruginosa or hospitalization that resulted in the use of parenteral antibiotics within the last 90 days.  

A term previously used to guide selection of antibiotic therapy was abandoned in the 2019 CAP guidelines. Introduced in previous guidelines, HCAP was a term used for patients who were not hospitalized but thought to have risk factors for antibiotic-resistant pathogens due to various exposures to the healthcare system. The new recommendation is to classify these types of risk factors as CAP. Additionally, it is recommended to cover for MRSA or P. aeruginosa only if local risk factors for the pathogens exist. This recommendation requires more research into site-specific data and was based on the increasing use of extended-spectrum antibiotics to treat MRSA and Pseudomonas despite the generally low prevalence of infectionat individual sites.

Another update to the 2019 ATS/IDSA CAP guidelines involves specific pharmacological therapy recommendations. The use of macrolide monotherapy for adults diagnosed with CAP in the outpatient setting was changed from a “strong” recommendation to a “conditional” recommendation based on local resistance patterns. Macrolides are recommended as monotherapy for healthy patients without comorbidities and a local pneumococcal resistance to macrolides <25%. This recommendation is based on evidence of macrolide failures that occurred due to macrolide-resistant Streptococcus pneumonia and a macrolide resistance rate >30%.

Additionally, the recommendation for standard empiric therapy of severe CAP in the inpatient setting was updated. The 2007 guidelines recommended the use of either a β-lactam/macrolide combination or a β-lactam/fluoroquinolone combination. The 2019 guidelines state that both combinations are still acceptable, but there is now stronger evidence available that favors the β-lactam/macrolide combination. The evidence used for this recommendation includes two meta-analyses of observational studies. Therefore, the guidelines indicate more research is needed.

Discussion and Clinical Impact: Overall, many recommendations found in the 2019 ATS/IDSA CAP guidelines were unchanged from the previous guideline. However, specific updates around diagnosis and treatment recommendations were highlighted. The new guidelines will help providers order appropriate tests and medication therapies for patients based on risk factors and diagnoses and therefore increase antimicrobial stewardship. Further updates beyond the major changes covered in this article can be found in the 2019 ATS/IDSA CAP guidelines.


  1. Metlay JP, Waterer GW, Long AC, et al. Diagnosis and treatment of adults with community-acquired pneumonia. An official clinical practice guideline of the American Thoracic Society and Infectious Diseases Society of America. Am J Respir. 2019 Oct 1; 200(7):45-67.

  2. Mandell LA, Wunderink RG, Anzueto A, et al. Infectious Diseases Society of America/American Thoracic Society consensus guidelines on the management of community-acquired pneumonia in adults. CID. 2007;44:S27-72.