In some states, patients who test positive for chlamydia or gonorrhea leave the clinic with not only a prescription for themselves, but also one for their sexual partner — who was not seen by a doctor.

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Thirty-eight states allow this public health measure known as expedited partner therapy, or EPT, which advocates say goes a long way in preventing sexually transmitted infections (STIs).

And states with the most permissible EPT laws may have the most success treating and preventing STIs, suggests a new University of Michigan study published online in the journal  Sexually Transmitted Infections.

Researchers analyzed reported chlamydia cases from 2000 to 2013 and found that, on average, disease incidence in states with prohibitive EPT legislation grew significantly faster than in states where EPT was allowed.

"We know that to most effectively treat and prevent STDs, we have to consider both the infected patient and his or her partners," says lead author Okeoma Mmeje, M.D., assistant professor of obstetrics and gynecology at Michigan Medicine and a member of the University of Michigan Institute for Healthcare Policy and Innovation.

"There are many barriers preventing people from making an office visit, from transportation and inconvenience to access to a free clinic," she says. "Allowing doctors to treat both patients and their partners in this way has proven to be effective at preventing reinfection and the spread of infections such as chlamydia and gonorrhea. Long term, there are many societal benefits both in health and cost."

Researchers found that in states where is EPT is prohibited, the average increase in the incidence of chlamydia infection is 17.5 cases per 100,000 per year, compared with 14.1 cases in states where EPT is permissible.

The benefits of expanded treatment access

National health organizations such as the Centers for Disease Control and Prevention and the American Congress of Obstetricians and Gynecologists have endorsed EPT, but it remains underused, Mmeje says.

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Many insurers don't cover medication costs for partners, and some doctors are hesitant to treat patients without an exam, citing liability concerns. The U-M team is researching barriers to practicing EPT in Michigan, where it is allowed.

Mmeje says that in states like Michigan, there are several steps in place to learn about a patient's partner's allergies before prescribing medication. Laws also protect against liability.

Chlamydia and gonorrhea are among the most treatable sexually transmitted diseases. But without intervention, they can cause serious and permanent health problems. Women may develop pelvic inflammatory disease, ectopic pregnancy and infertility. Men may experience discharge, painful urination and swollen testicles.

Societal costs of untreated STIs include the price of hospitalization and treatment down the road and a loss of productivity at work or in school for patients whose STIs lead to more serious medical conditions. Based on CDC data, Michigan experts estimate that even if EPT reduced the incidence of these diseases by 10 percent, it could save the state's health care system $1.6 million annually.

Yet infection rates are consistently high, particularly among youth, African-Americans and those living in Southern states. The vast majority of people with chlamydia and gonorrhea infections often do not present with symptoms, which may also prevent some people from seeking care.

"The rate of sexually transmitted diseases in our country, particularly among youth, continues to be a significant public health concern," Mmeje says.

"EPT helps circumvent some of the most common barriers to patients receiving the care they need. Our findings provide strong reasons to re-examine policies that make it difficult to access a public health measure that we know can help treat and prevent sexually transmitted diseases."