RT Journal
A1 Hurley JC
T1 ANtibiotic therapy in patients hospitalized with acute chronic obstructive pulmonary disease
JF JAMA
JO JAMA
YR 2010
FD September 22
VO 304
IS 12
SP 1325
OP 1327
DO 10.1001/jama.2010.1337
UL http://dx.doi.org/10.1001/jama.2010.1337
AB 
First, the authors used a discharge diagnosis of acute exacerbation of COPD to define the patient population from a retrospective cohort. As these authors noted, there is no validation of discharge coding as a method for identifying this category of patients. They excluded an unstated number of patients with pneumonia. However, without knowing what proportion received a chest x-ray and what the results of the chest x-ray were, the proportion who may have had pneumonia as an unrecognized diagnosis is uncertain. Unrecognized pneumonia, if present, would have had a pneumonia severity index (PSI) score2 of at least 70 (class 2, with a mortality risk of 0.6%) for an average patient of their study population based on the characteristics given in Table 1, and a higher score and mortality risk for the 25% who were older than 79 years. The difference in mortality between the groups that received or did not receive antibiotic treatment was less than 0.6% of 84 621 patients in their study. The observed difference could have been accounted for if less than 10% of the 17 392 patients not receiving antibiotic treatment had unrecognized pneumonia and a PSI score greater than 90 (class 4, with mortality risk of 9.5%).