How common is pneumococcal urinary antigen testing?
Despite guidelines recommending its use, pneumococcal urinary antigen testing, or UAT, is not performed often in the United States, even though it can help identify patients who are eligible for antibiotic de-escalation, researchers reported.
“The pneumococcal UAT is a useful test for identifying patients with pneumococcal pneumonia, most of whom do not require broad-spectrum antimicrobials. The IDSA recommends this test for patients with severe pneumonia, but we found that only 1 in 6 patients had it, even in the ICU,” Jennifer J. Schimmel, MD, assistant professor of medicine at Tufts University School of Medicine, told Infectious Disease News. “When it was ordered, though, physicians did pay attention to it.”
Importance of de-escalation
In a retrospective cohort study, Schimmel and colleagues searched the Premier database for adult patients admitted with community- or health care-associated pneumonia to 170 U.S. hospitals from 2010 to 2015. The analysis included 159,894 patients with pneumonia, of whom 15.5% had a UAT. They found that UAT was performed in 18.4% of ICU patients and 15.3% of non-ICU patients.
Joshua P. Metlay , MD, PhD, chief of the division of general internal medicine at Massachusetts General Hospital, called study “very elegant,” but said the value of UAT may be limited. He explained that UAT is “essentially, only recommended for patients with severe pneumonia,” as noted in the new community-associated pneumonia guidelines.
“Because [those are] often cases where broader spectrum antibiotics are being given and the microbiological data could be helpful,” Metlay told Infectious Disease News. “Frankly, it’s helpful to know the specific pathogen when patients are really sick. We’re generally not recommending that you do it routinely in all cases of patients with pneumonia, and certainly not in outpatients with pneumonia, and probably not in patients with non-severe inpatient pneumonia.”
In the study, the proportion of UAT testing ranged from 0% to 69% among hospitals with 100 or more eligible patients.
Patients with a positive UAT were more likely to have a positive Streptococcal pneumoniae culture and less likely to have resistant bacteria, Schimmel and colleagues reported. Specifically, 25.4% of patients with a positive UAT had a positive S. pneumoniae culture compared with 1.9% of patients with a negative UAT (P < .001), and 5.2% of patients with a positive UAT had resistant bacteria compared with 6.8% of patients with a negative UAT (P < .05).
According to the researchers, most patients who initially received broad-spectrum antibiotics were still being similarly treated 3 days later. However, among patients with a positive UAT, coverage was narrowed in 38.4% patients compared with 17% of patients with a negative UAT and 14.6% among untested patients.
The proportion of de-escalation after a positive UAT was “strongly correlated” with overall hospital rate of UAT, they reported. Additionally, only three patients were admitted to the ICU following UAT-prompted de-escalation.
Metlay said the significant takeaway is that a positive test helps with de-escalation.
“De-escalation is a really important thing that we need to have more of,” he said. “Infectious disease clinicians can point out the value of urinary antigen testing, particularly from the setting of ultimately de-escalating therapy.”
Need for RCTs
In a related editorial, Sameer S. Kadri, MD, MS, FIDSA, head of the clinical epidemiology section in the department of critical care medicine at the NIH Clinical Center, suggested the safety of de-escalation based on pneumococcal UAT cannot be determined from these findings.
“Given the overall low mortality rate of the population, a randomized trial with sufficient power to demonstrate a clinically relevant effect size of safety would likely require thousands of patients, which seems a bit unrealistic at least in the near future,” Kadri wrote. “Regardless, it seems that any future role of [pneumococcal UAT] in stewardship should be evaluated in a stable/stabilized lower risk inpatient population provided they are watched more closely post de-escalation for signs of deterioration.”
Metlay also underscored a lack of randomized controlled trials for pneumococcal UAT.
“We don’t have randomized trials showing that doing the test actually changes therapy, let alone the more important question which is improved outcome,” he said.
Schimmel acknowledged that more research is needed.
“Additional studies looking at antibiotic de-escalation after increased UAT testing and a study examining the economic impact of increased UAT testing [are needed],” Schimmel said. – by Marley Ghizzone
Disclosures: Kadri, Metlay and Schimmel report no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.