STI update: Testing, treatment, and emerging threats

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Release date: November 1, 2019
Expiration date: October 31, 2020
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Fast, sensitive molecular diagnostic tests that use urine or self-collected swabs may lead to more screening opportunities and be more acceptable to patients, resulting in faster and more accurate diagnosis and treatment of gonorrhea, chlamydia, trichomoniasis, and Mycoplasma genitalium infection.


  • Screen for gonorrhea and chlamydia annually—and more frequently for those at highest risk—in sexually active women age 25 and younger and in men who have sex with men, who should also be screened at the same time for human immunodeficiency virus (HIV) and syphilis.
  • Test for Trichomonas vaginalis in women who have symptoms suggesting it, and routinely screen for this pathogen in women who are HIV-positive.
  • Nucleic acid amplification is the preferred test for gonorrhea, chlamydia, trichomoniasis, and M genitalium infection; the use of urine specimens is acceptable.
  • Consider M genitalium if therapy for gonorrhea and chlamydia fails or tests for those diseases are negative.
  • Single-dose antibiotic therapy is preferred for chlamydia and uncomplicated gonorrhea. It is also available for trichomoniasis, although metronidazole 500 mg twice a day for 7 days has a higher cure rate.



Sexually transmitted infections (STIs) such as gonorrhea, chlamydia, and syphilis are still increasing in incidence and probably will continue to do so in the near future. Moreover, drug-resistant strains of Neisseria gonorrhoeae are emerging, as are less-known organisms such as Mycoplasma genitalium.

Now the good news: new tests for STIs are available or are coming! Based on nucleic acid amplification, these tests can be performed at the point of care, so that patients can leave the clinic with an accurate diagnosis and proper treatment for themselves and their sexual partners. Also, the tests can be run on samples collected by the patients themselves, either swabs or urine collections, eliminating the need for invasive sampling and making doctor-shy patients more likely to come in to be treated.1 We hope that by using these sensitive and accurate tests we can begin to bend the upward curve of STIs and be better antimicrobial stewards.2

This article reviews current issues surrounding STI control, and provides detailed guidance on recognizing, testing for, and treating gonorrhea, chlamydia, trichomoniasis, and M genitalium infection.


STIs are among the most common acute infectious diseases worldwide, with an estimated 1 million new curable cases every day.3 Further, STIs have major impacts on sexual, reproductive, and psychological health.

In the United States, rates of reportable STIs (chlamydia, gonorrhea, and syphilis) are rising.4 In addition, more-sensitive tests for trichomoniasis, which is not a reportable infection in any state, have revealed it to be more prevalent than previously thought.5


The medical system does not fully meet the needs of some populations, including young people and men who have sex with men, regarding their sexual and reproductive health.

Ongoing barriers among young people include reluctance to use available health services, limited access to STI testing, worries about confidentiality, and the shame and stigma associated with STIs.6

Men who have sex with men have a higher incidence of STIs than other groups. Since STIs are associated with a higher risk of human immunodeficiency virus (HIV) infection, it is important to detect, diagnose, and manage STIs in this group—and in all high-risk groups. Rectal STIs are an independent risk factor for incident HIV infection.7 In addition, many men who have sex with men face challenges navigating the emotional, physical, and cognitive aspects of adolescence, a voyage further complicated by mental health issues, unprotected sexual encounters, and substance abuse in many, especially among minority youth.8 These same factors also impair their ability to access resources for preventing and treating HIV and other STIs.

STI diagnosis is often missed

Most people who have STIs feel no symptoms, which increases the importance of risk-based screening to detect these infections.9,10 In many other cases, STIs manifest with nonspecific genitourinary symptoms that are mistaken for urinary tract infection. Tomas et al11 found that of 264 women who presented to an emergency department with genitourinary symptoms or were being treated for urinary tract infection, 175 were given a diagnosis of a urinary tract infection. Of these, 100 (57%) were treated without performing a urine culture; 60 (23%) of the 264 women had 1 or more positive STI tests, 22 (37%) of whom did not receive treatment for an STI.

Poor follow-up of patients and partners

Patients with STIs need to be retested 3 months after treatment to make sure the treatment was effective. Another reason for follow-up is that these patients are at higher risk of another infection within a year.12

Although treating patients’ partners has been shown to reduce reinfection rates, fewer than one-third of STIs (including HIV infections) were recognized through partner notification between 2010 and 2012 in a Dutch study, in men who have sex with men and in women.13 Challenges included partners who could not be identified among men who have sex with men, failure of heterosexual men to notify their partners, and lower rates of partner notification for HIV.

In the United States, “expedited partner therapy” allows healthcare providers to provide a prescription or medications to partners of patients diagnosed with chlamydia or gonorrhea without examining the partner.14 While this approach is legal in most states, implementation can be challenging.15


History and physical examination

A complete sexual history helps in estimating the patient’s risk of an STI and applying appropriate risk-based screening. Factors such as sexual practices, use of barrier protection, and history of STIs should be discussed.

Physical examination is also important. Although some patients may experience discomfort during a genital or pelvic examination, omitting this step may lead to missed diagnoses in women with STIs.16

Laboratory testing

Laboratory testing for STIs helps ensure accurate diagnosis and treatment. Empiric treatment without testing could give a patient a false sense of health by missing an infection that is not currently causing symptoms but that could later worsen or have lasting complications. Failure to test patients also misses the opportunity for partner notification, linkage to services, and follow-up testing.

Many of the most common STIs, including gonorrhea, chlamydia, and trichomoniasis, can be detected using vaginal, cervical, or urethral swabs or first-catch urine (from the initial urine stream). In studies that compared various sampling methods,17 self-collected urine samples for gonorrhea in men were nearly as good as clinician-collected swabs of the urethra. In women, self-collected vaginal swabs for gonorrhea and chlamydia were nearly as good as clinician-collected vaginal swabs. While urine specimens are acceptable for chlamydia testing in women, their sensitivity may be slightly lower than with vaginal and endocervical swab specimens.18,19

A major advantage of urine specimens for STI testing is that collection is noninvasive and is therefore more likely to be acceptable to patients. Urine testing can also be conducted in a variety of nonclinical settings such as health fairs, pharmacy-based screening programs, and express STI testing sites, thus increasing availability.

Screening recommendations and laboratory testing for common sexually transmitted infections

To prevent further transmission and morbidity and to aid in public health efforts, it is critical to recognize the cause of infectious cervicitis and urethritis and to screen for STIs according to guidelines.12 Table 1 summarizes current screening and laboratory testing recommendations.

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