Janson C, Johansson G, Ställberg B, et al.
Identifying the associated risks of pneumonia in COPD patients: ARCTIC an observational study.

Respir Res 2018;19(1):172.

Inhaled corticosteroids (ICSs) have been shown to increase the risk of pneumonia in patients with chronic obstructive pulmonary disease (COPD).1,2 Guidelines recommend that ICSs should only be used for treating COPD in patients who have asthma-COPD overlap or those who are at high risk of exacerbations.1,2 Despite this, ICSs are often prescribed to patients at low risk of exacerbations.1 

It can be hard to distinguish between acute exacerbations and pneumonia in patients with COPD because the symptoms of both are similar, so a chest radiograph should be used to confirm a pneumonia diagnosis. However, a recent research study by Finney et al.3 found that most patients with COPD who have consolidation shown on chest radiograph are discharged from hospital without a formal diagnosis of pneumonia. It is important that patients receive the correct diagnosis to make sure they get the right treatment and the incorrect use of ICSs is avoided. 

Another study by Janson et al.1 aimed to compare the risk of pneumonia in patients with COPD who were taking ICSs with that of patients with COPD who were not taking ICSs and with that of control patients without COPD. Additionally, the researchers examined the association between the severity of airflow limitation measured by FEV1 and comorbid asthma and the risk of pneumonia in patients with COPD. 

The authors analysed data from the ARCTIC observational study, a retrospective, observational cohort study of approximately 200,000 patients in 52 primary care centres in Sweden. The ARCTIC study collected electronic medical record data between 2000 and 2014 for patients who were diagnosed with COPD as well as reference patients. 

Janson et al.1 analysed data for 6,623 patients aged ≥40 years with a recorded diagnosis of COPD or COPD and asthma, and 48,566 reference control patients who were matched for age and sex, who did not have a diagnosis of COPD or asthma and who were not allowed to take ICSs. 

During the study period, 2,324 patients with COPD (35.1%) experienced at least one episode of pneumonia, compared with 5,036 reference patients (10.4%). Patients with COPD and FEV1 ≥50% who took ICSs had a 20–30% increased risk of pneumonia compared with patients not taking ICSs, while ICSs were associated with a five-fold increased risk of pneumonia in patients with COPD and asthma and in patients with FEV1 <50%. The risk of pneumonia was increased in patients with COPD and comorbid asthma, with the risk further increased if they were also taking ICSs. For all patients taking ICSs, the highest risk of pneumonia was found among those taking higher doses. 

The authors did point out some limitations to their large-scale study, including its retrospective design, a lack of information about mortality, smoking status, body mass index and patient-reported outcome data and, possibly significantly, pneumonia diagnoses that were made in primary and secondary care, which might not all have been confirmed by chest radiographs. However, they suggest that the association they found between ICS use and pneumonia in patients with COPD warrants a need for careful prescribing of ICSs for these patients.

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