CLEVELAND – A woman presents at the emergency department with painful or difficult urination, frequency and urgency.

If you guessed urinary tract infection, you might be wrong but you certainly aren’t alone.

EDs misdiagnose urinary tract and sexually transmitted infections in women nearly half the time, according to a report published recently in the Journal of Clinical Microbiology. The study team, led by researchers from Case Western Reserve University, notes that symptoms and even urinalysis results can be similar between the two conditions.

"Less than half the women diagnosed with a urinary tract infection actually had one," said Michelle Hecker, MD, an assistant professor in the Department of Medicine, Division of Infectious Diseases, MetroHealth Medical Center at Case Western. "Sexually transmitted infections were missed in 37% of the women, many of whom were wrongly diagnosed with urinary tract infections."

She called for revaluation of ED diagnostic testing strategies after the study, which included records from 264 women aged 18-65 who were seen at the MetroHealth ED. Urine samples provided by the women were retrieved and tested for gonorrhea, chlamydia, and trichomonas even when the tests were not been ordered as part of routine care.

The study points out that overdiagnosis of UTI leads to unnecessary antibiotic use as well as underdiagnosis of sexually transmitted infection. During the two-month observational cohort study, 64% of the patients with a missed STI were diagnosed as having UTI.

"An abnormal UA [urinalysis] result, seen in 92% of our subjects, was a common finding, poorly predicted the presence of a positive urine culture, and may also have contributed to the overdiagnosis of UTI,” study authors point out.

Furthermore, nearly a fourth of the patients diagnosed as having UTIs had no related symptoms or urine culture. Of 21 women who received antibiotic therapy within a week after urine culture, representing 8% of the total, 10 had had negative urine cultures, and 12 failed to receive optimal antibiotics for their condition, according to the report.

Overall, 175 of the patients had been diagnosed as having a UTI, although 57% had no urine culture performed during routine care. Even though 60 of the women had one or more positive STI tests, 37% received no treatment for that within seven days of the ED visit, according to the report.

“In this population, empiric therapy for UTI without urine culture testing and over-diagnosis of UTI were common and associated with unnecessary antibiotic exposure and missed STI diagnoses,” the authors conclude. “Abnormal UAs were common and not predictive of positive urine cultures.”