Infectious COPD exacerbations and value of chest radiography

Background: The most common cause of COPD exacerbations (AECOPD) is respiratory infections, mainly bacterial etiology. Pneumonia should be ruled out. Objectives: Determine infectious etiology of AECOPD, sensitivity (Se) and specificity (Sp)of chest radiography in order to rule out pneumonia. Materials and Methods: Retrospective study of inpatients due to AECOPD during 2019 winter period. Demographic characteristics, FEV1, DLCO, previous hospitalizations, long term oxygen therapy (LTOT), chronic non invasive ventilation (NIV) and enrolment in a rehabilitation program were recorded. Reverse transcriptase-polymerase chain reaction (RT-PCR) for 11 respiratory viruses performed on nasopharyngeal swabs, sputum samples and urinary antigen for St. pneumoniae were collected. Area under the ROC curve (AUC) was used for the diagnosis of pneumonia comparing chest radiography (Cr) and CT scan. Results: Fifty-three patients (mean age, 72.3 ±7.7 years; male, 56%) were included, the average BMI was 28.5±7.1Kg/m2 and 20% were current smokers. The mean of FEV1 was 44±15% and DLCO was 57.2±19.1% of the predicted. Half of patients had previous hospitalizations, 19% were with NIV, 34% with LTOT and 15% were in a respiratory rehabilitation plan. Infections accounted for 68% of the causes of exacerbation. Viral RT-PCR was positive in 24%, as were bacterial isolates. Cr showed AUC of 0.57±0.08, Se of 50%(IC95%: 26-74) and Sp of 64.7% (38.3-85.8) for the detection of consolidations (positive predictive value:39%). Conclusions: The most frequent cause of exacerbation was infectious, without differences between viral and bacterial isolation. Chest radiography proved to have low Se and Sp for the diagnosis of pneumonia.