A new study by UCSF Fresno researchers found implementation of a rapid test for gonorrhea and chlamydia (GC) significantly decreased the under- and overtreatment of these sexually transmitted infections in female patients seen in a hospital emergency department.
The study examined under- and overtreatment rates for two 70-week periods, before and after the hospital implemented a rapid, 90-minute nucleic acid amplification test (NAAT) for GC. Most hospital emergency departments (ED) use a test for GC that has a 24- to 48-hour turnaround time. Thus, the ED provider must guess at the result, and as a result, there are high undertreatment and overtreatment rates. The retrospective study, published in the Journal of Emergency Medicine online in March 2025, found that with the 90-minute test, undertreatment for the STIs went from 37% to 19%, and overtreatment went from 27% to 17%.
The study found that implementation of the rapid test prevented one patient from undertreatment for every five to six patients who were infected, and saved one patient from overtreatment for every eight to 12 patients who did not have GC.
The study looked at the pre-intervention and post-intervention time periods from 2017 to 2020 at Community Regional Medical Center (CRMC), in Fresno, said Brian Chinnock, MD, principal investigator of the study and UCSF Clinical Professor of Emergency Medicine at UCSF Fresno. CRMC implemented a 90-minute rapid NAAT test in the fall of 2018.
In real life, by using the 90-minute test “at our emergency department (CRMC), on average, with that intervention, per day, we’re preventing a patient from getting treated with an unnecessary antibiotic,” Dr. Chinnock said. The results also indicate that it means one or two patients per week who have chlamydia or gonorrhea are given antibiotics, who otherwise would leave the emergency department without treatment.
The study also examined under- and overtreatment rates at a control hospital, Clovis Community Medical Center (CCMC), where the standard 24-hour test was in use for the two 70-week time periods under review. The over- and undertreatment rates at CCMC remained substantially unchanged, at 37% and 40%, respectively, Dr. Chinnock said. CCMC has since changed to the 90-minute rapid test
It was especially pertinent to conduct the study in Fresno County, where rates of chlamydia (704.9 per 100,000) in 2023 and gonorrhea (204.4 per 100,000) are higher than in California (489.7 per 100,000 for chlamydia and 189.7 for gonorrhea). Nationwide, the two STI rates are 492.2 and 179.5 per 100,000, respectively.
The rapid test gives physicians information they need in time to provide appropriate treatment for patients who test positive for the STIs and to reduce the overuse of antibiotics for patients who test negative, he said.
“It’s been known in emergency medicine for a long time that the standard test we have had for gonorrhea or chlamydia takes more than 24 hours to come back. So, you’re not going to get a result during the time frame that the patients are there in the emergency department, and the emergency department physician has to do what is called ‘empiric therapy,’ which means guessing – giving your best guess at it.”
Taking guesswork out of treatment is important in two ways, Dr. Chinnock said. “We want to reduce the undertreatment number so that gonorrhea and chlamydia – this epidemic we are still in – does not keep going. And we don’t want to be doing a lot of overtreatments because the more you overtreat, then eventually antibiotic resistance goes up quicker. There are already not many drugs that can treat gonorrhea, and if we make the current antibiotics resistant, that’s going to be a huge problem. In addition, patients are subjected to the additional cost and antibiotic side effects of an unnecessary antibiotic treatment.”
The rapid test is expensive, but Dr. Chinnock said the study shows it is probably a new, better standard of care, and emergency departments should consider implementing it. “I think the majority of emergency departments in this country have the old test, which is still the 24-hour test, and you’re guessing at the results. Unfortunately, our best estimates don’t do very well compared to testing.”
Any study has limitations, and Dr. Chinnock said the biggest limitation is that this is a retrospective study, meaning you’re looking back at previous data and things that happened. “It’s always possible that when you are collecting the data that it wasn’t done properly, but we list how we did it, and we took a lot of time to make sure we got the correct data,” he said.
The study also labeled a case as undertreatment if the patient left the emergency department without treatment, even if the patient was called back and received care. “So, you could say, ‘Well, what if they were called back and got the correct treatment?’ But the whole point of this is that you should not have a process that relies on calling back patients,” Dr. Chinnock said. “First of all, it’s very resource-intensive, it requires a lot of extra money and time to have someone make the call back, and it’s not reliable. We have so many patients whose telephone numbers have changed, and the numbers they give us are lines that are not in service. It’s just not the best way to do it.”
Additional UCSF-Fresno co-authors of the study are Gilbert Ramirez, MD, a UCSF Associate Clinical Professor of Emergency Medicine; Gayle Kouklis, MD, a UCSF Volunteer Clinical Instructor of Emergency Medicine; and Christopher Teran, MD, a UCSF-Fresno Emergency Medicine resident who was a San Joaquin Valley Program in Medical Education (SJV PRIME) medical student at the time of the study. Informatics was through Community Health System, and UC Merced provided biostatistics support.
Established in 1975, UCSF Fresno is celebrating 50 years of training doctors and improving health in the San Joaquin Valley this year. A regional campus of the UCSF School of Medicine, UCSF Fresno offers training in eight medical residency programs, one dental surgery residency program and 20 Accreditation Council on Graduate Medical Education (ACGME) and non-ACGME sub-specialty fellowships. UCSF Fresno plays a vital role in expanding access to health care in the Valley, training physicians and medical students for the region and state, conducting research that addresses regional health issues, and academically preparing students from the San Joaquin Valley to pursue careers in health and medicine.
