Screening and Treating STIs
Ordering STD or STI tests
Chlamydia DNA probe
Gonorrhea DNA probe
HIV Test
Syphilis (RPR or VRDL)
Hepatitis B Testing (if not immunized)
Trichomonas RNA PCR (NAAT) is new CDC recommendation. Vaginal Wet prep is okay but misses many true cases of trich.
Consider Urinalysis
Testing for STIs generally involves a blood test and/or self-collection of relevant body fluid specimens.
** Anal pap smears for gay men and others who engage in anal sex.
| STI | Test | Comments | Specimen used | Rx | Partner Rx |
| HIV | -Screen with either: HIV 1 & 2 Ab screen, OR HIV1 & 2 Ab + P24 antigen (preferred). -Confirm with: Multispot (a replacement for Western blot.). See below. |
At DRMC, in Cerner, you can order: HIV 1 & 2 Ab Screen HIV 1 & 2 Rapid Ab screen POC HIV / RNA Quant PCR The confirmation is reflex Western blot |
Blood, serum | Work with the social worker; check laws about notifying partner. Test partner |
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| HBV | HBsAg, HBsAb, HBcAb, |
Blood | |||
| HCV | HCV antibody | Blood | |||
| Neisseria Gonorrhea | NAAT
*Plus culture if you are concerned for resistance. |
Dual therapy: Treat for chlamydia as well since it is 4 times more common. |
Men: 1st-catch urine (preferred), or urethral swaps. Women: 1st-catch urine or vaginal or cervical swabs (preferred). *May do NAAT on rectal swabs or oropharyngeal swabs to evaluate for infection there. |
Dual therapy. -Ceftriaxone 250mg IM x 1 PLUS Azithromycin 1g PO x 1 or Doxycycline 100mg PO BID x 7d if a pt can’t take azithromycin. Alt: If ceftriaxone unavailable, use PO Cefixime (not 1st-line 2/2 to increased drug resistance); Azithromycin 2g PO x 1 if pt is allergic to cephalosporins. |
Partners from the past 60d should be treated. No need to test them (empiric tx ok) |
| Chlamydia trachomatis | NAAT | 4 times more common than gonorrhea. | Men: 1st-catch urine (preferred), or urethral swaps. Women: Vaginal or cervical swabs (preferred) or 1st-catch urine *May do NAAT on rectal swap to evaluate for rectal infection. |
Azithromycin 1g PO x 1 Alt: Doxycycline 100mg BID x 7 days if not pregnant. |
Partners from the past 60d should be treated. No need to test them (empiric tx ok) |
| Trichomonas Vaginalis | NAAT (Ribosomal RNA PCR) preferred over cervical wet prep by new CDC guidelines. | *The Top (most common) STD in the U.S. Trichomonas is the only top cause of vaginitis that is also an STI. Candida and BV are not STIs. |
Men: 1st-catch urine (preferred) or swab or brush Women: Vaginal or cervical swabs (preferred) collected during pap smear or 1st-catch urine. |
Metronizadole 2g PO x 1 or Tinidazole 2g PO x 1; or Metronidazole 500mg BID x 7d. **Reinfection rates are high (20% at 3 months). Consider rescreening. |
Abstain from sex until both partners are treated. |
| Syphilis | Nontreponemal tests -VDRL -RPR Treponemal test -FTA-ABS -TP-PA -TP-EIA |
Treponema Pallidum (spirochete). Incubation = 21d on average but can be 3-90d. |
-Darkfield microscopy of primary lesions. -Blood |
Primary, secondary, or early latent: Benzathine PCN 2.4 million units IM x 1 (risk of Jarisch-Herxheimer reaction); Alt: Doxycycline 100mg PO BID x 14d or Azithromycin 2g PO x 1 (less effective) Late / tertiary: Consult ID. PCN as above IM weekly x 3 wks or doxy x 4 weeks. Neuro: IV PCN 4 Million q4hs or Ceftriaxone 2g IV aq x 10-14d; Monitory RPR titers and repeat LP over 12-24 months. |
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| HPV | Cytology and/or HPV testing of cervical or anal specimens. | -Cervical swabs, (usually as co-testing) -Anal swabs. |
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| HSV1 /2 | -HSV culture and HSV PCR. In patients with active genital sores, the preferred methods of testing for the virus are the herpes culture and HSV DNA testing (PCR). –PCR testing is preferred if encephalitis or neonatal herpes are suspected. –HSV IgM or IgG ab testing. The antibody test is not as sensitive as PCR or culture. Only use it if you can’t Cx or do PCR. |
-Cx takes 2 or more days to complete. The Cx can give false negatives if there is not enough active virus in the sample, which can occur if the lesion is cultured more than 48 hours after the symptoms appear. –PCR is more sensitive than Cx. It is useful in circumstances where the virus is present in low numbers (such as viral encephalitis) or if the lesion is several days old. |
-Swab from an open sore for Cx or PCR -Swab from a blister, blood, spinal fluid, etc for PCR. |
-FTA-ABS (Fluorescent treponemal antibody absorbed); TP-PA (T. Pallidum particle agglutination); EIA (Enzyme Immunoassays)
-Nucleic Acid Amplification Test (NAAT)
Cx = Culture
Additional resource: See pg 219 in small red Ob/GYN book.
“The U.S. Preventive Services Task Force (USPSTF) has issued recommendations on behavioral counseling to prevent sexually transmitted infections (STIs) and recommendations about screening for individual STIs. Clinicians should obtain a sexual history to assess for behaviors that increase a patient’s risk. Community and population risk factors should also be considered. The USPSTF recommends intensive behavioral counseling for all sexually active adolescents and for adults whose history indicates an increased risk of STIs. These interventions can reduce STI acquisition and risky sexual behaviors, and increase condom use and other protective behaviors. The USPSTF recommends screening for chlamydia and gonorrhea in all sexually active women 24 years and younger, and in older women at increased risk. It recommends screening for human immunodeficiency virus (HIV) infection in all patients 15 to 65 years of age regardless of risk, as well as in younger and older patients at increased risk of HIV infection. The USPSTF also recommends screening for hepatitis B virus infection and syphilis in persons at increased risk. All pregnant women should be tested for hepatitis B virus infection, HIV infection, and syphilis. Pregnant women 24 years and younger, and older women with risk factors should be tested for gonorrhea and chlamydia. The USPSTF recommends against screening for asymptomatic herpes simplex virus infection. There is inadequate evidence to determine the optimal interval for repeat screening; clinicians should re-screen patients when their sexual history reveals new or persistent risk factors.” (Am Fam Physician. 2016 Dec 1;94(11):907-915.)
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* Nucleic acid amplification tests (polymerase chain reaction, ligase chain reaction) for the diagnosis of Chlamydia trachomatis and Neisseria gonorrhoeae.
Table of Contents
HIV
Syphilis
“Is a systemic disease caused by a spirochete Treponema Pallidum.
Nontreponemal tests: VDRL and RPR titers correlate with disease activity; become nonreactive after treatment; false-positives may be associated with other medical conditions.
Treponemal tests: Detect treponemal antibodies using a variety of techniques, e.g. fluorescent treponemal antibody absorbed (FTA-ABS), T. Pallidum particle agglutination (TP-PA) or automated enzyme immunoassays (EIA); usually remain positive regardless of treatment and disease activity; 15-25% may become nonreactive 2-3 years after treatment.
Testing sequence: First, do a nontreponemal test (VDRL or RPR). If the nontreponemal test is positive, then confirm with a treponemal test (TP-PA, FTA-ABS, or EIA). That’s how testing for syphilis is usually done. However, now some labs first perform automated, inexpensive treponemal tests for syphilis IgG.
If you have a patient with a painful ulcer which has been present for only one week. You highly suspect syphilis but you get an RPR or VRDL and it’s negative. What should you do? Repeat it in two weeks. Why? Because these tests become positive within 3 weeks of the appearance fo the primary chancre, so they may be negative in a patient with an early infection.
Neisseria gonorrhea
See table above.
Chlamydia trachomatis
See table above.
Trichomonas Vaginalis
T. vaginalis — NAAT on vaginal swabs (preferred) or urine
***The latest CDC guidelines recommend a Nucleic Acid Amplification Test (NAAT), a form of molecular testing, as the preferred method when testing for trichomoniasis. NAAT delivers 100% sensitivity and high specificity for trichomonas, whereas sensitivity and specificity of the wet mount are low. NAAT is highly sensitive, often detecting three to five times more T. vaginalis infections than wet-mount microscopy, a method with poor sensitivity (51%–65%). Click here for CDC recommendations for treating Trichomonas.
***Molecular methods, such as the APTIMA Trichomonas vaginalis Assay, offer the highest sensitivity and specificity for detection of trichomoniasis. The APTIMA test utilizes target capture, transcription-mediated amplification (TMA), and hybridization protection assay (HPA) technologies for detection of Trichomonas vaginalis ribosomal RNA (rRNA).
The advent of urine-based tests and the utility of self-collected vaginal swabs has increased the acceptance of STI screening among patients and providers since it allows for routine specimen collection without a pelvic examination or swab of the urethra.
HPV
See table above.
Resources
http://www.aafp.org/afp/2016/1201/p907.html
https://www.uptodate.com/contents/screening-and-diagnostic-testing-for-hiv-infection
https://www.uptodate.com/contents/screening-for-sexually-transmitted-infections