What is the proper screening process for HIV (Human Immunodeficiency Virus) and hepatitis C?

Proper Screening for HIV and Hepatitis C

Hepatitis C Screening

All adults aged 18-79 years should receive universal, one-time screening for hepatitis C using anti-HCV antibody testing with reflex HCV RNA PCR testing. 1, 2

Initial Screening Strategy

• Use a two-step reflex testing approach that requires only a single blood collection: Step 1 involves HCV-antibody testing using an FDA-approved assay, followed immediately by Step 2 with reflex HCV RNA PCR testing if antibody-positive 1
• This reflex approach eliminates the need for a return visit for confirmatory testing and addresses a major barrier in the HCV care continuum 1
• Screening should be voluntary with an opt-out approach where patients are informed that HCV testing will be performed unless they decline 1, 2

Who Requires Screening Beyond Universal Recommendation

• All pregnant women during each pregnancy, as HCV prevalence has doubled in women aged 15-44 years from 2006 to 2014 1
• Persons younger than 18 years with risk factors, particularly injection drug use history 1
• Persons older than 79 years with risk factors should be considered for screening 1

Periodic Screening for High-Risk Groups

• Annual testing is specifically recommended for people who inject drugs and men with HIV who have unprotected sex with men 1
• Persons with continued risk for HCV infection should be screened periodically, with frequency determined by individual risk assessment 1

Special Testing Situations

• For recent exposure (within 6 months): If initial antibody test is negative, perform HCV RNA testing or follow-up HCV-antibody testing ≥6 months after exposure 1
• For immunocompromised patients: Consider direct HCV RNA testing, as antibody production may be delayed or inadequate 1
• For patients at risk for reinfection: Use HCV RNA testing since antibody tests will remain positive after prior clearance 1
• For rural or difficult-to-access populations: Dried blood spot collection can be used for sequential antibody and reflex RNA testing, requiring only a fingerstick rather than venipuncture 1

Interpreting Test Results

• Positive antibody with positive RNA: Current (active) HCV infection requiring evaluation for treatment 1
• Positive antibody with negative RNA: Past resolved infection or false positive; patient does not have current infection but is not protected from reinfection 1
• Negative antibody: No evidence of current or past infection, unless recent exposure or immunocompromised 1

Screening-Test-Positive Samples Require Specific Handling

• For screening-test-positive samples with high signal-to-cutoff (s/co) ratios (>95% predictive of true positive): Can be reported as anti-HCV-positive without supplemental testing, though a comment should indicate that <5% might be false-positives 3
• For screening-test-positive samples with low s/co ratios: Perform reflex supplemental testing, preferably RIBA (recombinant immunoblot assay) 3
• The anti-HCV result should not be reported until additional test results are available 3

HIV Screening

HIV-infected patients should be screened for hepatitis C virus (HCV) infection using enzyme immunoassays (EIAs) licensed for detection of antibody to HCV (anti-HCV) in blood. 3

Confirmatory Testing for HIV Patients

• Positive anti-HCV results must be verified with additional testing such as recombinant immunoblot assay (RIBA) or reverse transcriptase polymerase chain reaction for HCV RNA 3
• HCV RNA testing should be assessed in HIV-infected persons with undetectable antibody but other evidence of chronic liver disease (e.g., unexplained elevated liver-specific enzymes) or when acute HCV infection is suspected 3

Special Considerations for HIV-HCV Co-infection

• Nucleic acid testing is the most sensitive means of diagnosing acute HCV infection in HIV-infected patients, as only 20% of HCV RNA-positive samples are simultaneously positive for HCV antibody 4
• Patients with HIV become antibody-positive on average 7 months after HCV RNA is detected 4
• A serological assay offering combined detection of antibody and antigen enhances sensitivity of detection compared to antibody-only assays in HIV patients 4

Risk-Based Screening Populations

• History of blood transfusions or organ transplantation prior to 1992 3
• Persons who have injected illicit drugs 3
• Persons with HIV infection, hemophilia, or on hemodialysis 3
• Children born to mothers infected with HCV 3
• Health care providers after needle stick injury or mucosal exposure to HCV-positive blood 3

Screening After Accidental Exposure

• Baseline testing for anti-HCV and serum ALT level should be performed immediately after exposure 3
• If anti-HCV is negative: Perform HCV RNA assay 4-6 weeks after exposure for early diagnosis 3
• Follow-up testing for anti-HCV and serum ALT level should be performed 4-6 months after exposure even if baseline tests were negative 3

Critical Pitfalls to Avoid

• Do not rely solely on antibody testing, as this can miss active infection or incorrectly classify resolved infections as current 1
• Do not miss diagnosis in high-risk groups, especially in people who inject drugs or immunocompromised patients 1
• Do not delay confirmatory testing, as patients are frequently lost to follow-up between antibody and confirmatory testing 1
• Do not use only antibody testing in previously infected patients, as this will miss reinfection 1
• Do not assume risk-based screening is sufficient, as it failed to identify the majority of individuals with HCV infection due to both clinician and patient barriers 1