Sexually transmitted infection screening (GYN): Clinical sciences

Sexually transmitted infections, or STIs, are infections that are transmitted through sexual contact. The goal of screening for STIs is to diagnose and treat infections, and provide education, which then prevents further transmission. While some STIs cause symptoms such as lesions or cervical discharge, many are asymptomatic. STI screening is encouraged for all patients, and specifically in special populations such as pregnant patients, where some STIs, like syphilis, can cause congenital disease.

When a patient presents for STI screening, begin with a focused history and physical exam. Start by reviewing your patient’s age, pregnancy status, and HIV status. Ask your patient if they have had a known exposure to an STI. If yes, inquire about the timing of sexual exposure, review previous screenings or treatment results, and ask if they’re experiencing symptoms.

On a physical exam, look for cervical discharge or genital lesions which may prompt additional screening. Also keep in mind that STI screening can be completed at a specific STI screening visit or as part of a preventative visit, like a well-patient care exam. STI screening can also be completed without a physical exam by patient-collected swabs, and lab tests such as blood and urine tests; however, this is only appropriate for asymptomatic patients.

Okay, let’s start by talking about which infections are screened for and how that screening is completed. Chlamydia, caused by Chlamydia trachomatis, is the most frequently reported bacterial STI with the highest prevalence in patients who are under 25 years of age. Gonorrhea, caused by Neisseria gonorrhoeae is the second most frequently reported bacterial STI. Testing for both is completed through a nucleic acid amplification test or NAAT. If a provider obtains a sample for testing, a specimen collection swab is used to obtain the sample from the patient’s cervix. If the patient collects their own sample, either a vaginal swab or first catch urine specimen can be used. Positive results are reported to the CDC.

On the other hand, Trichomoniasis, caused by Trichomonas vaginalis, is not a reportable disease. That being said, it has a higher prevalence rate than gonorrhea or chlamydia, and is known to increase the risk of acquiring HIV. Testing is done by a NAAT test using a cervical or vaginal swab, or a first catch urine sample. NAAT is preferred for its increased specificity and sensitivity, but screening can also be completed via wet mount microscopy with visualization of motile trichomonads, which confirms the diagnosis. When it comes to HIV, screening is typically completed by using an antigen/antibody test for HIV 1 and 2. Positive test results are reportable to the CDC.

Next, screening for syphilis, which is caused by Treponema pallidum, is usually completed by a 2-step process. A non-treponemal test is obtained first, either a Venereal Disease Research Laboratory, or VDRL; or Rapid Plasma Reagin, or RPR. This is followed by a treponemal test, such as the T. pallidum passive particle agglutination, or TP-PA test. A positive test is reportable to the CDC.

Now, hepatitis B screening has traditionally been done by checking for hepatitis B surface antigen or HBsAg. However, the CDC now recommends the triple panel test. This panel is composed of HBsAg; antibody to hepatitis B surface antigen, or anti-HBs; and total antibody to hepatitis B core antigen, or total anti-HBc. This test is recommended because there can be a window during an acute infection when the HBsAg and anti-HB are both negative. During this window, the only test that can accurately detect an acute infection is the total anti-HBc. Positive results are reported to the CDC. Additionally, there’s a hepatitis B vaccine that should be offered to those at risk who have not been previously infected or vaccinated. Keep in mind that the vaccine will not clear the virus any faster, but that there’s also no risk to vaccinating someone who is already infected.

Moving on, hepatitis C screening is simple and is done by checking for HCV antibodies. Positive results are reported to the CDC.

Now, screening for human papillomavirus, or HPV, looks for high-risk types of the human papilloma virus, and is usually co-tested along with routine cervical cancer screenings, as indicated based on age and previous screening. Also, the HPV vaccine is recommended for all patients ages 11 to 26. For patients aged 27 to 45, vaccination can be considered using shared-decision making.

Finally, screening for herpes simplex virus, or HSV, is only indicated when a patient has a suspicious genital lesion. These lesions are initially painful and vesicular, and are followed by ulceration. A prodromal period of tingling or itching may precede their appearance. HSV testing is done by obtaining a swab of fluid from the ulcer, which is analyzed by polymerase chain reaction, or PCR for both HSV 1 and 2.

While traditionally HSV 1 was thought to only cause oral herpes or cold sores and HSV 2 only caused genital outbreaks, evidence shows that either strain of the virus can cause an outbreak in either area. Additionally, all patients who have suspicious lesions should also have serology testing for type-specific antibodies to HSV 1 and 2.