What laboratory tests are required to evaluate and monitor a patient for hepatitis C infection?

Laboratory Testing for Hepatitis C Infection

Begin with HCV antibody testing with automatic reflex to HCV RNA testing if the antibody is reactive—this single blood draw approach is the most efficient method to diagnose current hepatitis C infection. 1

Initial Screening Protocol

• Use an FDA-approved HCV antibody test (either laboratory-based enzyme immunoassay or point-of-care rapid test like OraQuick) as the first-line screening test 1
• Request reflex HCV RNA testing when ordering the antibody test—this allows automatic RNA testing if antibody is reactive, avoiding the need for a second blood draw and improving patient follow-through 1, 2
• The reflex approach requires only a single venipuncture and eliminates a major barrier in the continuum of care 1

Confirmatory Testing with HCV RNA

• HCV RNA by nucleic acid test (NAT) is mandatory to confirm active infection after a reactive antibody test 1
• Use an FDA-approved NAT assay with detection sensitivity ≤25 IU/mL 2
• HCV RNA detected = current active infection requiring treatment evaluation 1, 2
• HCV RNA not detected = past resolved infection or false positive antibody (resolved infection is most common) 1, 3, 2

Interpretation of Results

Antibody Nonreactive

• No HCV antibody detected—no further testing needed unless recent exposure suspected 1, 2

Antibody Reactive + RNA Detected

• Current active HCV infection—proceed to pretreatment assessment 1, 2

Antibody Reactive + RNA Not Detected

• Past resolved infection or false positive antibody result 1, 3
• Patient should be informed they do not have active infection but are not protected from reinfection 1
• To distinguish false positive from resolved infection, consider testing with a different HCV antibody assay platform 1, 2

Special Population Considerations

Recent Exposure (<6 Months)

• Test HCV RNA directly or repeat HCV antibody at 6 months post-exposure, as antibodies may not have developed yet 1, 2

Immunocompromised Patients

• Consider HCV RNA testing even with negative antibody, as antibody development may be delayed or absent 1, 2

Suspected Reinfection

• Use HCV RNA testing directly in patients with prior spontaneous or treatment-related clearance, as antibody will remain positive 1, 2

Pretreatment Assessment for Confirmed Active Infection

Once active HCV infection is confirmed (RNA positive), obtain the following:

Baseline Viral Assessment

• Quantitative HCV RNA to document baseline viral load before treatment 1, 2
• HCV genotype testing if it may alter treatment recommendations 1, 2

Liver Function and Disease Severity

• Hepatic function panel: ALT, AST, bilirubin, albumin 1
• Platelet count and prothrombin time/INR 1
• Calculate FIB-4 score for cirrhosis assessment (FIB-4 >3.25 suggests cirrhosis) 1
• Liver biopsy is not required for treatment decisions 1

Coinfection Screening

• HIV testing (overlapping risk factors and affects treatment planning) 1
• Hepatitis B surface antigen (HBsAg) and antibodies (HBV coinfection accelerates liver damage) 1
• Hepatitis A antibody to assess immunity (vaccinate if non-immune) 1
• Consider screening for other sexually transmitted infections based on risk factors 1

Post-Treatment Monitoring

• Quantitative HCV RNA at 12 weeks or later after completing therapy to confirm sustained virologic response (SVR = cure) 1
• Hepatic function panel to document transaminase normalization 1
• If transaminases remain elevated after SVR, assess for other causes of liver disease 1

Critical Pitfalls to Avoid

• Never diagnose active HCV infection based on antibody alone—always confirm with HCV RNA before considering treatment 1, 3, 2
• Do not assume positive antibody means current infection—20% of infections clear spontaneously, leaving persistent antibodies 1, 3
• Do not skip RNA testing in immunocompromised patients even with negative antibody, as they may have active infection without detectable antibody response 1, 2
• Remember that positive antibody after successful treatment is expected—use RNA testing to detect reinfection 1, 2