Sesgos de confusión por indicación y gravedad en estudios observacionales

Influence of previous use of inhaled corticoids on the development of pleural effusion in community-acquired pneumonia

RATIONALE

Previous use of inhaled corticosteroids (ICS) in patients with chronic obstructive pulmonary disease has been associated with increased risk of community-acquired pneumonia. However, ICS have been associated with fewer pneumonia complications and decreased risk of pneumonia-related mortality.

OBJECTIVES

The objective of the study was to assess the influence of previous use of ICS on the incidence of parapneumonic effusion in patients with different baseline respiratory disorders.

METHODS

We conducted a single-center cohort study of 3,612 consecutively collected patients diagnosed with community-acquired pneumonia. We assessed clinical, radiographic, and pleural-fluid chemistry and microbiologic variables. Patients were classified according to whether or not they received prior ICS treatment.

MEASUREMENTS AND MAIN RESULTS

A total of 633 patients (17%) were treated with corticosteroids before the diagnosis of pneumonia (chronic obstructive pulmonary disease, 54%; asthma, 13%). Incidence of parapneumonic effusion was lower in patients with ICS use compared with non-ICS patients (5% vs. 12%; P < 0.001). After matching according to propensity scores (n = 640), prior treatment with corticosteroids was still significantly associated with a lower incidence of parapneumonic effusion (odds ratio, 0.40; 95% confidence interval, 0.23-0.69; P = 0.001) compared with patients without ICS treatment. Prior ICS treatment was associated with higher levels of glucose (P = 0.003) and pH (P = 0.02), and lower levels of protein (P = 0.01) and lactic acid dehydrogenase (P = 0.007) in the pleural fluid.

CONCLUSIONS

Prior treatment with ICS in a population of patients with different respiratory chronic disorders who develop pneumonia is associated with lower incidence of parapneumonic effusion.