Discussion
pleural effusion, pneumonia, AECOPD, pulmonary edema, purulence, COPD
PLEURAL EFFUSION, PNEUMONIA, PULMONARY EDEMA, COPD
Our study highlights the challenge of diagnosing AECOPD. The data indicates a limited utility of clinical and/or laboratory findings to distinguish classical AECOPD from AECOPD associated with other acute processes/illnesses. Among the 3 symptoms listed in the clinical criteria of AECOPD diagnosis, all were associated with AECOPD in univariate analysis. However, none of the clinical symptoms analyzed could differentiate AECOPD alone from AECOPD with other acute process. Not surprisingly, our study found that elevated venous pCO2 was associated with a diagnosis of AECOPD while radiographic findings of pleural effusion suggested against AECOPD, and radiographic evidence of pulmonary edema or pneumonia suggest against AECOPD only diagnosis. This is consistent with existing literature [Interestingly, approximately 12% of patients in our study did not have AECOPD by our adjudication criteria but were labeled as such on admission. Unfortunately, there is limited literature available on the incidence of misdiagnosis of exacerbation, but this does highlight the challenge of making a diagnosis of AECOPD. One reason the diagnosis of AECOPD can be so challenging may be related to frequency of misdiagnosis of COPD in the general population. In Ontario, only one third of patients in the general population labeled with COPD have received spirometry to confirm the diagnosis [Our determination of whether a patient’s presentation of AECOPD was accompanied by another condition was potentially limited by subjectivity since a reference standard is lacking in the field. The manifestations of AECOPD are protean, non-specific, and could represent a variety of non-AECOPD conditions. The GOLD report recommends that differential diagnoses are excluded before making a diagnosis of AECOPD [Increased sputum purulence was shown to be associated with the presence of bacteria in the lower respiratory tract [The study’s major limitation was the small sample size which limited our ability to fit many variables in the multivariate analysis. Other limitations include the subjective adjudication of definition based on clinical presentation and retrospective nature of the study which did not allow for assessment of detailed time course of clinical symptoms and laboratory parameters. Additionally, some laboratory parameters such as C-reactive protein, procalcitonin, BNP, or D-dimer which could help discern AECOPD from AECOPD with other acute processes/illnesses were not included because these tests were not consistently measured in all study patients.This study highlighted the difficulty of AECOPD diagnosis. We identified increased sputum purulence and venous pCO2 to be predictors for AECOPD, but pleural effusion on chest radiographs suggested against AECOPD. A more accurate and specific clinical tool to diagnose AECOPD with different phenotypes is needed.