Pneumonia Diagnostic Shows Limited Utility


The streptococcal pneumoniae urine antigen (SPUA) test was studied over the course of a year to determine if it provided any benefits in terms of diagnostic capability or aided in reducing empirical antibiotic use.

image of lungs

Although the gold clinical standard for diagnosing pneumonia has been the chest X-ray to see if there is inflammation in the lungs, the streptococcal pneumoniae urine antigen test was developed to enhance the microbiologic diagnosis of respiratory illness.

The gold clinical standard for diagnosing pneumonia has been the chest X-ray to see if there is inflammation in the lungs. Secondary tests typically include blood tests, such as a complete blood count (CBC) to see if there is an infection, and the use of a pulse oximetry, which, of course, measures how much oxygen is in the blood.1

Although, there can be clinical situations where issues arise and there are difficulties around diagnosis, especially if there is limited or no access to X-rays, for example.2

Another clinical issue around proper diagnosis includes antimicrobial stewardship, especially as it relates to lower respiratory tract infections (LRTI). In a recent, large prospective study, it was reported that of the 29% of people given an antibiotic during their initial medical visit who were experiencing LRTI, there was no effect on the duration or overall severity of cough compared to those who didn’t receive an antibiotic.2,3

A new study presented at this week’s Society for Healthcare Epidemiology of America (SHEA) conference examined a novel diagnostic, the streptococcal pneumoniae urine antigen (SPUA) test, developed to enhance the microbiologic diagnosis of pneumonia. Specifically, this assay can identify pneumococcal antigens excreted into the urine.

The study’s investigator pointed to concerns over the diagnostic including the test’s sensitivity and inability to change outcomes by reducing antibiotic use. However, the cost-effectiveness and real-world clinical utility of the test had yet to be determined.

What You Need to Know

  • While chest X-rays have been the gold standard for diagnosing pneumonia, there are situations where access to such diagnostic tools may be limited, leading to difficulties in diagnosis.
  • The overuse of antibiotics in treating lower tract respiratory infections, such as pneumonia, has been highlighted as a concern.
  • The streptococcal pneumoniae urine antigen (SPUA) test may have potential benefits in enhancing microbiologic diagnosis, but concerns remain regarding its sensitivity, impact on clinical outcomes, and cost-effectiveness. Further research is needed to evaluate its real-world clinical utility and cost-effectiveness.

Study Parameters and Results

From June 1, 2022, through May 31, 2023, patients who underwent a SPUA test in the MUSC Health System were identified using Epic SlicerDicer. Those with a positive test result had their charts reviewed. For the study, 1518 patients underwent a SPUA test over the course of 1 year. Sixty-two patients (4%) tested positive. Of these patients, 14 were discharged before the test results were available. The average time to receive test results was 2.2 days.4

A comparison of antibiotic therapy from the day before to 2 days after the test results revealed that only 7 additional patients were switched to a targeted antibiotic regimen.4

Antibiotics were categorized as either “broad” or “targeted” for S pneumoniae. Targeted categories included penicillins without beta-lactamase inhibitors, first-third generation cephalosporins, doxycycline, levofloxacin, or moxifloxacin (with or without azithromycin), and azithromycin alone. Broad categories included fourth generation or higher cephalosporins, carbapenems, penicillins with beta-lactamase inhibitors, and vancomycin.4

“These findings align with other real-world studies indicating a positive test prevalence of 4-8%, with 15-30% of patients transitioning to targeted antibiotics after a positive outcome,” the lead investigator wrote. “The total cost of the SPUA tests was approximately $44,022, based on a unit price of $29 per test, yet their practical utility remains limited.”4

1. Pneumonia Diagnosis. National Heart, Lung and Blood Institute. Updated March 22, 2022. Accessed April 18, 2024
2. Merenstein DJ, Barrett B, Ebell MH. Antibiotics Not Associated with Shorter Duration or Reduced Severity of Acute Lower Respiratory Tract Infection. J Gen Intern Med. Published online April 15, 2024. doi:10.1007/s11606-024-08758-y
3. Antibiotics Aren’t Effective for Most Lower Tract Respiratory Infections. Georgetown University Medical Center press release. April 11, 2024. Accessed April 18, 2024.
4. Burton J. Impact of Streptococcus pneumoniae Urinary Antigen Testing in a Large Academic Medical Center. Presented at: SHEA 2024; April 16-19; Houston, TX. Poster #66

Related Videos
© 2024 MJH Life Sciences

All rights reserved.