What blood tests are recommended for comprehensive STD screening?

Comprehensive Blood Tests for STD Screening

Blood tests for STD screening should include serologic testing for syphilis, HIV, and hepatitis B, with additional tests based on risk factors and sexual practices. 1

Core Blood Tests for STD Screening

Essential Blood Tests:

• Syphilis serology: Most laboratories use a reverse screening algorithm with treponemal-specific test first (EIA/chemiluminescence immunoassay) followed by nontreponemal test (RPR) for confirmation 2, 1
• HIV antibody/antigen test: Recommended for all patients seeking STI evaluation 1
• Hepatitis B surface antigen (HBsAg): Essential for comprehensive screening 2, 1

Additional Blood Tests Based on Risk:

• Hepatitis C antibody: Particularly recommended for men who have sex with men (MSM) and those with risk factors 1
• Type-specific HSV-2 serologic testing: Recommended for high-risk individuals, especially those with HIV infection or partners with genital herpes 1, 3

Testing Considerations by Population

High-Risk Individuals:

• More frequent screening (every 3-6 months) for patients with:
  • Multiple or anonymous partners
  • Previous STI diagnosis
  • Substance use, especially methamphetamine
  • Sex work or partners who engage in sex work 1

Men Who Have Sex with Men (MSM):

• All core blood tests plus:
  • Hepatitis C antibody screening
  • Type-specific HSV-2 serologic testing
  • Extragenital site testing (rectal, oropharyngeal) for gonorrhea and chlamydia 2, 1

Pregnant Women:

• Serologic testing for syphilis during early pregnancy
• Hepatitis B surface antigen testing
• HIV testing at first prenatal visit and third trimester 2, 1

Important Clinical Considerations

Test Performance:

• Syphilis serology sensitivity varies by stage:
  • Primary syphilis: 61-100% sensitivity
  • Secondary syphilis: 100% sensitivity
  • Late latent syphilis: 61-75% sensitivity 2

Common Pitfalls:

1. Failing to screen partners: 25-40% of treatment "failures" are actually reinfections from untreated partners 2, 1
2. Missing window periods: Recent infections may not be detectable immediately
3. Overlooking extragenital infections: Testing only urogenital sites in high-risk individuals will miss infections at other sites 2, 1
4. Biological false positives: Can occur with syphilis testing, particularly in patients with HIV, hepatitis B, or hepatitis C 2

Complementary Non-Blood Testing:

While not blood tests, comprehensive STD screening should also include:

• Nucleic acid amplification tests (NAATs) for chlamydia, gonorrhea, and trichomonas on appropriate specimens (urine, vaginal/cervical swabs) 1, 4
• Site-specific testing based on sexual practices (rectal, pharyngeal) 2, 1

Reporting Requirements

Positive tests for chlamydia, gonorrhea, syphilis, chancroid, and HIV require reporting to public health authorities according to local requirements 2, 1

Remember that blood tests are just one component of comprehensive STD screening. The combination of appropriate blood tests with nucleic acid amplification testing provides the most thorough approach to detecting sexually transmitted infections.