When should repeat testing for blood‑borne pathogens (human immunodeficiency virus, hepatitis B virus, hepatitis C virus) be performed after a known occupational or significant exposure?

Repeat Laboratory Testing After Bloodborne Pathogen Exposure

After occupational exposure to bloodborne pathogens, repeat testing should be performed at baseline, 6 weeks, 3 months, and 6 months for HIV; at 4-6 months for hepatitis C; and at 1-2 months after the final vaccine dose for hepatitis B. 1

HIV Follow-Up Testing Schedule

The CDC guidelines establish a clear testing algorithm for HIV exposure:

• Baseline testing immediately after exposure 1
• 6 weeks post-exposure 1, 2
• 3 months post-exposure 1, 2
• 6 months post-exposure for final clearance 1, 2

Test immediately at any point if acute retroviral syndrome symptoms develop, regardless of the scheduled timeline. 2 Approximately 81% of healthcare workers who seroconvert experience acute retroviral syndrome at a median of 25 days after exposure. 3

Extended HIV Follow-Up

For healthcare workers who become infected with HCV following exposure to a source coinfected with HIV and HCV, extend HIV testing to 12 months. 2 This extended surveillance is critical because coinfection may alter seroconversion kinetics.

Hepatitis C Follow-Up Testing Schedule

The HCV testing algorithm differs significantly from HIV:

• Baseline testing for anti-HCV and ALT immediately after exposure 1, 4
• 4-6 months post-exposure for follow-up anti-HCV and ALT testing 1, 4
• Optional HCV RNA at 4-6 weeks if earlier diagnosis is clinically desired 1, 4

No post-exposure prophylaxis exists for HCV, making surveillance the primary management strategy. 1, 4 Confirm repeatedly reactive anti-HCV enzyme immunoassays with supplemental tests. 1

Hepatitis B Follow-Up Testing Schedule

For HBV exposures where vaccine is administered:

• Test for anti-HBs response 1-2 months after the last vaccine dose 1, 4

Critical Caveat for HBV Testing

Anti-HBs response to vaccine cannot be accurately assessed if HBIG was received in the previous 3-4 months. 1 This is a common pitfall—delay antibody testing if HBIG was administered to avoid false interpretation of vaccine response.

Additional Monitoring Requirements

Healthcare workers on HIV post-exposure prophylaxis require evaluation within 72 hours of starting PEP and monitoring for drug toxicity at least every 2 weeks. 1, 4 This toxicity monitoring is separate from seroconversion surveillance and addresses medication adverse effects.

Advise exposed persons to use precautions to prevent secondary transmission during the entire 6-month follow-up period. 1, 4 This includes barrier protection during sexual activity and avoiding blood/tissue donation.

Common Pitfalls to Avoid

• Don't skip the 6-month HIV test: While most seroconversions occur by 6-7 weeks (median 46 days), HIV antibody is detectable in ≥95% of patients only by 6 months. 3 Rare delayed seroconversions beyond 6 months have been documented. 3

• Don't test discarded needles or syringes for virus contamination—this is not recommended and provides unreliable information. 1

• Don't forget to encourage follow-up completion: Healthcare facilities should develop systems to actively encourage exposed workers to return for testing, as compliance rates remain suboptimal even after high-risk exposures. 1