What is the recommended initial test for patients suspected of having Hepatitis C (HCV) virus?

Initial Testing for Hepatitis C Virus Infection

The recommended initial test for patients suspected of having Hepatitis C virus infection is an anti-HCV antibody test using an FDA-approved assay, which should be followed by HCV RNA testing if the antibody test is positive. 1, 2

Diagnostic Algorithm

Step 1: Initial Screening

• Begin with anti-HCV antibody testing as the first-line diagnostic test for all patients with suspected chronic HCV infection 1
• FDA-approved tests include both laboratory-based enzyme immunoassays (EIA) and rapid point-of-care tests (such as OraQuick HCV Rapid Antibody Test), which have similar sensitivity and specificity 2, 3
• These assays are highly sensitive and specific in immunocompetent persons 1

Step 2: Confirmatory Testing Based on Antibody Results

If anti-HCV antibody is NEGATIVE:

• No further testing is needed unless the patient has recent exposure (within 6 months), ongoing risk behaviors (e.g., current injection drug use), or is severely immunocompromised 1, 3
• For recent exposure, either direct HCV RNA testing or repeat antibody testing 6 months after exposure is recommended 3

If anti-HCV antibody is POSITIVE:

• Immediately proceed to HCV RNA testing using a sensitive nucleic acid test (NAT) to distinguish between active infection and past resolved infection 1
• An FDA-approved NAT with a lower limit of detection <15 IU/ml is recommended, though assays detecting <25 IU/mL are acceptable 1, 3
• Both qualitative and quantitative HCV RNA tests are acceptable for this purpose 1

Step 3: Interpretation of Combined Results

Anti-HCV positive + HCV RNA positive:

• Confirms current active HCV infection requiring medical evaluation and potential treatment 2, 3
• These patients need referral for further evaluation and care 1

Anti-HCV positive + HCV RNA negative:

• Indicates either past resolved infection or a false-positive antibody test 2, 3
• No current infection present; no treatment needed 1
• For suspected recently acquired infection, retest HCV RNA at 12 and 24 weeks to confirm definitive clearance 1

Special Testing Considerations

Immunocompromised Patients

• HCV RNA testing should be part of the initial evaluation alongside antibody testing, as antibodies may be undetectable in profoundly immunosuppressed patients (e.g., HIV/AIDS, hemodialysis patients) 1, 3
• Anti-HCV antibodies may be delayed or absent in these populations 3

Suspected Acute Hepatitis C

• Begin with both anti-HCV antibody AND HCV RNA testing simultaneously 1
• Antibodies may be undetectable in the early phase of acute infection (first 5-6 weeks), while HCV RNA becomes detectable within 1-2 weeks of infection 1

Patients at Risk for Reinfection

• For persons with previous spontaneous or treatment-related viral clearance who have ongoing risk factors, HCV RNA testing is the primary test since antibodies will remain positive from prior infection 2, 3
• Reinfection is confirmed by demonstrating a different genotype or distantly related strain by phylogenetic analysis 1

Efficient Testing Approach

Reflex testing is the most efficient strategy:

• Collect blood for both tests at the initial visit 3
• If anti-HCV is reactive, the same sample is automatically reflexed to HCV RNA testing 3
• This approach minimizes delays and ensures patients don't require a second visit for confirmatory testing 3

Common Pitfalls to Avoid

• Never rely solely on antibody testing without confirmatory HCV RNA testing, as this leads to misdiagnosis of active infection 3
• Do not assume a positive antibody test means active infection—approximately 20% of patients spontaneously clear the virus but remain antibody-positive 4
• Do not dismiss testing in patients with normal liver enzymes—approximately 50% of HCV-infected patients have normal transaminase values, yet the majority still have histological liver disease 1
• Remember that ALT levels fluctuate and correlate poorly with disease severity 1
• In immunocompromised patients, do not accept a negative antibody test as ruling out infection without HCV RNA testing 3

Alternative Testing When RNA Assays Unavailable

• HCV core antigen can be used as a surrogate marker of viral replication when HCV RNA assays are not available or affordable 1
• Core antigen assays are less sensitive (lower limit of detection equivalent to approximately 500-3,000 HCV RNA IU/ml) 1
• Where sensitive HCV RNA assays are unavailable, a qualitative HCV RNA assay with detection limit <1,000 IU/ml can broaden access to diagnosis 1