Background

Sexually transmitted infections (STIs) are caused by organisms acquired through sexual activity.¹ The most common STIs diagnosed in the emergency department (ED) include Neisseria gonorrhoeae, Chlamydia trachomatis, Trichomonas vaginalis, syphilis, herpes viruses, human immunodeficiency virus (HIV), and human papillomaviruses. STIs in the ED can range from asymptomatic to having vaginal or penile discharge, genital‐urinary pain, abdominal pain, urethritis, cervicitis, tubo‐ovarian abscesses, orchitis, and epididymitis.^1–4 Long‐term complications for some untreated STIs can include pelvic inflammatory disease (PID), infertility, increased risk for ectopic pregnancy, acquisition of HIV, and continued community transmission of the infection.

Screening for STIs can occur in the ED for at‐risk patients who may have limited outpatient access to medical care.⁴ Assessing patients’ risk for STIs in the ED can be challenging because ED providers may not ask for detailed sexual histories and patients may not provide honest answers about their sexual behavior. Obtaining an accurate STI risk assessment can be particularly difficult with nonemancipated adolescents or in the setting of unrecognized human trafficking or spousal abuse.⁵ Pad‐based screening allowing patients to respond nonverbally while awaiting ED evaluation could be an approach to overcome socially difficult interactions.^6,7 Race and gender are associated with disparities in STI testing and treatment in ED settings.⁸ ED physicians often fail to adhere to Centers for Disease Control (CDC) Guidelines for the diagnosis and treatment of STIs, a trend that has continued for almost two decades.^9,10 The CDC recommended diagnostic tests for N. gonorrhoeae, C. trachomatis, and T. vaginalis are the nucleic acid amplification tests (NAATs).¹¹ NAAT testing can occur from genital swab or be obtained from the urine. While urine specimens are easier to obtain and provide 99% specificity, sensitivities range from 88% to 93% for Chlamydia and 88% for gonorrhea compared with endocervical specimens.^12,13 Unfortunately, the results of the NAATs are usually not available during the clinical encounter resulting in significant under‐ and overtreatment of ED patients for STIs.^14–16 In addition, some settings lack access to NAAT or other STI testing that provides faster results.¹⁷ Nonetheless, the future of STI testing likely includes rapid diagnostic tests where the results can be available during the patient encounter.¹⁸

In this chapter, we focus on N. gonorrhoeae, C. trachomatis, and T. vaginalis. We do not address HIV, herpes, or syphilis. For additional information, readers are referred to the CDC, “Sexually Transmitted Diseases Treatment Guidelines, 2015.”¹¹

Clinical question

Can a urinary tract infection (UTI) be reliably differentiated from a STI based on history and physical exam?

Urinary symptoms such as dysuria and frequency are common chief complaints in the ED, and the differential diagnoses include both UTIs and STIs (see Chapter 32).¹⁹ UTIs predominantly affect women and occur in all ages, whereas N. gonorrhoeae and C. trachomatis are predominantly seen in nonwhite younger male or female sexually active patients. When urinary symptoms are reported a pelvic exam is less likely to be performed.²⁰ A prospective cohort study of 92 adult female ED patients with urinary frequency, urgency, dysuria, and no new or changes in their vaginal discharge found that combining the history, physical examination finding, and urine dip was 50% sensitive (CI 23–77%) and 86% specific (CI 76–93%) for an STI.²¹ Sexual histories obtained in the ED are often inadequately documented, patients may not provide accurate information, and ED providers perform insufficient STI testing even when the medical history suggests a STI.^20,22–26

Reed et al.²⁷ analyzed 250 adolescent females who received STI testing and found that being of black race (odds ratio [OR] = 3.2), having a new partner within the last 3 months (OR = 1.9), cervical discharge (OR = 2.0), absence of yeast (OR = 3.3), and >10 white blood cells (OR = 2.5) on vaginal Gram stain predicted a STI. The model was only 75% sensitive and 71% specific, with a negative predictive value of 85%. There have been two clinical prediction tools developed for STIs in the ED though neither has been externally validated.²⁸ The first model for estimating risk of N. gonorrhoeae and C. trachomatis in men in the ED included: ≤24 years of age, penile discharge, and contact with someone infected with N. gonorrhoeae or C. trachomatis, and lack of health insurance status.²⁹ The other model utilized a point‐system and the following variables: age, marital status, education, new sex partner within past 2 years, non‐ED as a primary source for health care, nonantibiotic use past month, dysuria, or discharge in the past 3 months.²⁸ The latter prediction model had area under the receiver operating curve (ROC) of 0.64 for females and 0.72 for males.²⁸ Other models derived and validated outside ED settings seek to guide testing for asymptomatic gonorrhea or chlamydia.^30,31 Before widespread incorporation into ED practice, these STI models must better define discrimination, calibration, reliability, external validity, comparative usefulness, and viable implementation strategies.³² The components of an adequate sexual history in the ED are highlighted in Table 34.1. Risk factors for STI acquisition and high‐risk groups are summarized in Tables 34.2 and 34.3.

Clinical question

Are the history and physical exam useful for diagnosing STIs?

The CDC considers the clinicians’ history and physical examination “foundational” for diagnosing and treating STIs.^43,44 Sexual histories can identify patients that are at high risk for STIs, but the history and physical exams done in the ED do not accurately differentiate between patients that have STI or UTI.^14,20,23,44

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