The approach to diagnosing community-acquired pneumonia could be called into question after a new study suggests clinicians are getting it wrong in nearly a third of patients.

The study of 319 people with a clinical diagnosis of community-acquired pneumonia (CAP) found that 30% of patients who were deemed to have CAP based on the presentation and chest X-ray had no evidence of pneumonia on CT scan.

Also, one-third of patients who had no change on chest X-ray had CT changes consistent with pneumonia found the study published in the American Journal of Respiratory Critical Care Medicine.

In a related editorial, Professor Grant Waterer a Professor of Medicine at the University of Western Australia says the findings could shift the current assessment of the diagnosis of CAP from “we might occasionally get it wrong” to “Houston we have a problem.”

“If this is confirmed by at least another study, it’s going to cause significant change to the way we think about pneumonia and what we may do to diagnose and confirm it,” he told the limbic.

We may need to start back at the beginning and redefine the aetiology and outcomes of patients with CAP-like presentations based on a CT gold standard overriding the chest X-ray interpretation, he explained.

“The implications for everything from empiric therapy to reimbursement and quality of care measures are enormous,” he said.

“In Australia, one of the conditions that is determined nationally, in terms of the quality of healthcare in hospitals, is mortality rate from CAP, so if many of the patients that we think have CAP don’t, or in fact some do but we don’t call it CAP, then that whole benchmark or standard is highly questionable.”

Moving forward, Professor Waterer believes there needs to be more studies not only to clear up the uncertainly, but also to provide clear data on what to do if a clinician sees a CAP-like syndrome but decides pneumonia is not present on chest X-ray.

At the moment, if we decide soft radiological changes are not pneumonia, then we have no clear clinical pathways, no metrics to tell us quality of care is being met and in some settings possibly reimbursement issues, he said.

He thinks clinicians may be overcalling the diagnosis of CAP based on chest X-rays because deciding that pneumonia might be present based on soft radiological changes allows them to go down a well-validated clinical pathway.

However, he hopes the study might now make them think twice about making a diagnosis of pneumonia if the chest X-ray only has subtle changes.