What tests and diagnosis code should be included for annual sexually transmitted disease (STD) testing on a lab slip?

Annual STD Testing: Lab Order Writing and Diagnosis Coding

For annual sexually transmitted disease screening, order a comprehensive panel including HIV antibody/antigen, syphilis serology (treponemal-specific test or RPR), gonorrhea and chlamydia NAAT (urine or genital swab), hepatitis B surface antigen, and hepatitis C antibody, using ICD-10 code Z11.3 (encounter for screening for infections with a predominantly sexual mode of transmission) for asymptomatic screening. 1

Core Tests to Order on Lab Slip

Blood Tests

• HIV testing: Order HIV-1/2 antibody/antigen combination test (enzyme immunoassay) 1
• Syphilis: Order treponemal-specific test first (EIA/chemiluminescence immunoassay) followed by RPR for confirmation using reverse screening algorithm 2, 1
• Hepatitis B: Order HBsAg at minimum; consider adding HBcAb and anti-HBs for complete immunity assessment 1
• Hepatitis C: Order hepatitis C antibody 1

Urine or Genital Swab Tests

• Gonorrhea and Chlamydia: Order nucleic acid amplification test (NAAT) - this is the preferred method with highest sensitivity (86.1%-100%) and specificity (97.1%-100%) 3
  • For women: Can use urine, endocervical swab, or vaginal swab 2
  • For men: First-void urine is acceptable 2
  • Critical caveat: For high-risk populations (men who have sex with men), also order extragenital site testing (rectal and oropharyngeal swabs) for gonorrhea and chlamydia 2, 1

Additional Tests for Women

• Trichomonas: Order NAAT for all women as part of comprehensive screening 1

Appropriate ICD-10 Diagnosis Code

Use Z11.3 - "Encounter for screening for infections with a predominantly sexual mode of transmission" 1

This code is specifically designed for asymptomatic annual screening and should be accepted by most laboratories and insurance carriers for preventive testing. 4

Risk-Based Modifications

For High-Risk Populations Requiring More Frequent Testing

• HIV-positive individuals: Screen every 3-6 months rather than annually, especially with multiple partners or unprotected intercourse 1
• Men who have sex with men (MSM): Screen every 3-6 months and always include extragenital sites (rectal, oropharyngeal) 1
• Age considerations: Mandatory chlamydia and gonorrhea screening for all sexually active women under 25 years; consider for those ≥25 years based on risk factors 1

Common Pitfalls to Avoid

Specimen Collection Errors

• Timing matters: For urine NAAT testing, use first-void urine (first part of urination) for optimal sensitivity 2
• Don't forget extragenital sites: Missing rectal and pharyngeal testing in MSM population leads to 53%-100% of infections being undetected, as these are frequently asymptomatic 3
• Transport requirements: Most NAAT specimens can be maintained at room temperature, but confirm with your specific laboratory 2

Testing Algorithm Confusion

• Syphilis screening: Most laboratories now use reverse algorithm (treponemal test first, then RPR), not the traditional RPR-first approach 2, 1
• False positives: Syphilis RPR/VDRL can have biologic false-positives (typically low titer <1:8) in injection drug users 1

Documentation Issues

• Partner notification: When any STI is detected, document that sexual contacts must be evaluated and treated to prevent reinfection, as most "treatment failures" represent reinfection from untreated partners 2, 1
• Reporting requirements: Positive tests for chlamydia, gonorrhea, syphilis, and HIV require reporting to local health departments per state requirements 2

Sample Lab Order Format

Write on lab slip:

• "Annual STD screening panel"
• HIV-1/2 Ag/Ab combo
• Syphilis EIA (with reflex RPR if positive)
• Hepatitis B surface antigen
• Hepatitis C antibody
• Gonorrhea/Chlamydia NAAT (specify: urine OR genital swab)
• Trichomonas NAAT (for women)
• Diagnosis code: Z11.3

Add for MSM patients:

• Gonorrhea/Chlamydia NAAT - rectal swab
• Gonorrhea culture - pharyngeal swab (NAAT not FDA-cleared for pharyngeal chlamydia) 2