What information should be entered on the requisition when ordering a hepatitis C RNA quantitative viral load (PCR)?

What to Put on a Hepatitis C Viral Load Requisition

When ordering an HCV RNA quantitative viral load test, you must specify: (1) HCV RNA quantitative assay with a sensitive method (lower limit of detection ≤50 IU/mL), (2) specimen type (serum or plasma), and (3) the clinical indication (diagnosis, pretreatment assessment, or treatment monitoring). 1

Essential Requisition Information

Test Specifications

• Request "HCV RNA Quantitative" or "HCV Viral Load" using a real-time PCR or transcription-mediated amplification (TMA) method 1
• The assay should have a lower detection limit of 12-15 IU/mL (modern assays) or at minimum ≤50 IU/mL 2, 1
• Results must be reported in International Units per milliliter (IU/mL), not copy numbers 1

Specimen Requirements

• Specimen type: Serum or plasma (EDTA or plasma preparation tube) 3
• Critical handling: Serum must be separated from cellular components within 2-4 hours of collection 4
• Storage: Preferably frozen at -20°C or -70°C if not processed immediately 4
• Transport: Room temperature acceptable if processed within 2 hours; frozen samples must be protected from thawing during shipping 4

Clinical Information to Include

Specify the purpose of testing:

• Confirmatory diagnosis (following positive anti-HCV antibody)
• Pretreatment baseline assessment (requires both quantitative viral load AND genotyping) 1
• Treatment monitoring (on-treatment or post-treatment response)
• Acute infection evaluation (when anti-HCV may still be negative) 1

Additional Testing Considerations

When to Add Genotyping

HCV genotype must be ordered simultaneously with baseline viral load before initiating treatment 1. This determines:

• Treatment regimen selection
• Ribavirin dosing (if applicable)
• Treatment duration
• Need for resistance testing with certain direct-acting antivirals 3

For genotype 1 infections requiring certain DAA regimens, you may also need to specify resistance-associated substitution (RAS) testing for NS3, NS5A, or NS5B regions 3.

Laboratory Selection

Use the same laboratory for all serial measurements (baseline, during treatment, and post-treatment) because different laboratories can vary in viral quantification results despite standardization 1, 5. This ensures accurate assessment of viral load changes, particularly the critical 2-log₁₀ reduction at week 12 of treatment.

Common Pitfalls to Avoid

1. Don't order qualitative HCV RNA for treatment monitoring: While older qualitative assays (detection limit 50 IU/mL) were previously used for diagnosis, modern quantitative assays with detection limits of 12-15 IU/mL are now preferred for both diagnosis and monitoring 1

2. Don't use quantitative assays as the sole endpoint of treatment: Sustained virologic response (SVR) is defined as undetectable HCV RNA at 24 weeks post-treatment, requiring an assay with lower limit of detection <50 IU/mL 1

3. Avoid specimen handling errors: Failure to separate serum within 2-4 hours or allowing frozen samples to thaw can produce false-negative results 4

4. Don't forget immunocompromised patients: In patients on hemodialysis, with HIV coinfection, transplant recipients, or those with hypogammaglobulinemia, HCV RNA testing may be needed even with negative anti-HCV antibody 1