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PO-CAP shows clinical differences vs. B-CAP
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In a clinical comparison, researchers determined that patients with postobstructive community-acquired pneumonia, or PO-CAP, had a longer duration of symptoms and a more common occurrence of weight loss than those with bacterial community-acquired pneumonia, or B-CAP.
Also among the findings published in Clinical Infectious Diseases, Michael S. Abers, MD, of Massachusetts General Hospital and Harvard Medical School, and colleagues noted that bacteria were the cause of PO-CAP in just 3% of the cases they studied, indicating a diminished need for antibiotics.
“Although there is substantial overlap,” they wrote, “PO-CAP is a clinical entity distinct from B-CAP.”
The researchers studied 259 consecutive patients hospitalized for community-acquired pneumonia (CAP) at a Veterans Affairs hospital in Houston between July 2011 to June 2012. Among the patients, 5.4% were identified as having PO-CAP, defined as “the radiographic appearance of a pulmonary infiltrate occurring distal to an obstructed bronchus.” The researchers increased the number of PO-CAP patients in their study by screening all CAP admissions for another year and enrolling only those with PO-CAP, bringing it to 30 patients.
Compared with B-CAP patients (n = 60) who were identified during the initial 1-year study, the PO-CAP patients had a longer duration of symptoms (median, 14 vs. 5 days; P < .001) and were more than twice as likely to lose more than 5% of their body weight (67.9% vs. 32.7%; P = .003). Cavitary lesions were more common and leukocytosis was less common in patients with PO-CAP, according to the researchers, who noted that a bacteria pathogen was implicated in just 10% of PO-CAP cases. Although no differences were observed in disease severity or rates of ICU admissions, 30-day mortality was greater in PO-CAP vs B-CAP patients (40.0% vs 11.7%; P < .01), they wrote.
“Overlap with B-CAP, however, limits the possibility of making a clinical distinction at the time of admission in an individual case,” the researchers concluded. “Given the strong evidence against a role for bacterial pathogens, results of the present study should encourage more limited antibiotic use in patients with PO-CAP. Our experience has been that when patients fail to respond to a first course of antibiotics, physicians repeat sputum cultures, which now are contaminated with newly acquired gram-negative colonizing organisms, and then give additional antibiotics to ‘cover’ these newly recognized bacteria.
“The results of our study strongly oppose this kind of medical management. If a patient fails to defervesce with a first course of antibiotics, full attention should be focused on treating the obstructing lesion.”
Symptom duration, weight loss differentiate PO-CAP
In a related editorial, Antoni Torres, MD, PhD, and Miguel Ferrer, MD, PhD, both of the Hospital Clinic of Barcelona, wrote about the study’s findings on PO-CAP that, “probably the most important and notably different features are duration of symptoms and [a greater than 5%] weight loss.”
Torres and Ferrer, however, wrote that Abers and colleagues compared PO-CAP cases only with cases of proven or confirmed bacterial CAP, when up to 50% to 70% of cases have no microbial diagnosis. Further, it is unknown whether the differences shown by the researchers would remain significant against the total cohort of patients with CAP.
They also noted the significantly higher 30-day mortality rates in PO-CAP patients (40% to 11.7%) but said further studies should cover cause and time of death after admission.
“In summary, postobstructive lung infection is a syndrome that can mimic CAP and that needs a different diagnostic approach, including CT and bronchoscopy,” Torres and Ferrer wrote. “A careful clinical history, including duration of symptoms and weight loss, might help clinicians suspect this entity. Antibiotics are probably advisable in febrile patients.” – by Gerard Gallagher
Disclosure: The researchers report no relevant financial disclosures.
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