‘Meaningless’ urine culture results prompt clinicians to look for solutions
More than half of the urine cultures collected at two primary care clinics during a recent 16-month period were contaminated, according to data presented during the virtual Society for Healthcare Epidemiology of America Spring Meeting.
Urine cultures are the "most common microbiological tests in the outpatient setting," according to Michael Allen Hansen, MD, MPH, MS, an assistant professor at Baylor College of Medicine, and colleagues. Yet, most studies on urine collection have focused on the process in the ED or in-patient settings.
Therefore, they analyzed urine cultures from 1,265 adults (mean age, 43.2 years; 84% women; 68.1% born outside the United States) collected from November 2018 to March 2020 at two publicly funded primary care clinics in Houston. The most common comorbidities among the patients were obesity (34.1%), hypertension (26%) and diabetes (20.4%).
According to the researchers, 55% of urine cultures were contaminated, 24% were positive for uropathogens and the remaining 21% showed no growth.
Study senior author Larissa Grigoryan, MD, PhD, an assistant professor in the department of family and community medicine at Baylor College of Medicine, told Healio Primary Care that the contamination rate was the highest she had ever seen.
“Studies have shown some clinics have contamination rates as low as 1% and in others, it is as high as 42%,” she said. “In our study ... more than half of urine cultures had meaningless results.”
According to Grigoryan, one reason for so many contaminated cultures “could be the high number of obese patients, for whom it’s physically difficult to carry out the midstream clean-catch urine collection technique.”
Other potential reasons include low health literacy levels and comprehension of the English language in the study cohort and a reticence among health care professionals to give a detailed description on how to collect urine, Grigoryan continued.
She said she is applying for a grant to help develop an intervention, perhaps one with pictorial or video instructions, that would decrease decontamination rates.
“A contamination rate of 1% might not be realistic, but I hope the rate will be lower, much lower, than what we have now,” Grigoryan said.