Elevated procalcitonin levels in response to bacterial infection might help ‘lazy doctors’ when deciding on antibiotic treatment in patients hospitalised with community-acquired pneumonia but the test is no substitute for a competent clinical assessment, according to Professor Grant Waterer from Royal Perth Hospital.
“In fact, the test might be harmful if therapy is inappropriately withheld,” he said.
Speaking in a debate on the role of the procalcitonin, he said clinicians are still forced to rely on empirical treatment early in the course of severe pneumonia at a stage in the disease when conventional microbiology had little to offer.
“We know that, if the infection is bacterial, timely administration of appropriate antibiotics is critical,” he said. “Treatment within three hours of presentation predicts better survival, and the risk-benefit balance strongly favours empiric therapy.”
Procalcitonin – the natural precursor to calcitonin – is generally elevated by bacterial infection but unaffected, or even suppressed, by viral infection, and has been proposed as a tool to detect sepsis and guide treatment.
“In bacteraemia it is elevated more by gram-negative rather than gram-positive organisms, and there is wide inter-patient variability in the response,” Professor Waterer said.
“Within populations the average level does increase with bacterial infection, but we treat individuals, not populations, so there is the risk of false negative results. Some retrospective studies have identified cases of Legionella infection, for example, that would not have been treated if the results had been followed.”
In addition, bacterial and viral co-infection in pneumonia is common, complicating interpretation of a procalcitonin response.
Professor Waterer also questioned the rationale for attempting to restrict antibiotic therapy in severe pneumonia, noting that mortality and readmission are not the only outcomes that matter.
“Pneumonia is also associated with increased long-term mortality as well as an increase in ischaemic heart disease and stroke, which are predicted by persistent inflammation,” he said.
“Because of costs like these, we need to be very cautious in withholding antibiotics on the basis of a single test.
“My view is that procalcitonin adds little to competent clinical care.”
Dr Thomas File from Akron, Ohio, argued that procalcitonin can assist in reducing the over-use use of antibiotics in treating community-acquired pneumonia, but it would always be an ancillary role in the total package of care.