What laboratory tests should be done before initiating treatment?

Laboratory Tests Required Before Initiating Treatment

Before initiating treatment for hepatitis C virus (HCV) infection, specific laboratory tests should be performed within 12 weeks prior to starting antiviral therapy, including complete blood count with differential, international normalized ratio, hepatic function panel, thyroid-stimulating hormone (if interferon will be used), and calculated glomerular filtration rate. 1

Essential Pre-Treatment Laboratory Tests

Within 12 Weeks Before Starting Therapy

• Complete blood count with differential
• International normalized ratio (INR)
• Hepatic function panel, including:
  • Albumin
  • Total and direct bilirubin
  • Alanine aminotransferase (ALT)
  • Aspartate aminotransferase (AST)
  • Alkaline phosphatase
• Calculated glomerular filtration rate (GFR)
• Thyroid-stimulating hormone (only if interferon-based therapy will be used)

At Any Time Before Starting Therapy

• HCV genotype and subtype determination
• Quantitative HCV viral load (except when viral load won't influence treatment duration)

Assessment of Drug-Drug Interactions

Assessment of potential drug-drug interactions with concomitant medications is recommended prior to starting HCV therapy 1. This is particularly important as many HCV medications have significant interactions with commonly prescribed drugs.

Additional Testing Considerations

Resistance Testing

Routine monitoring for HCV drug resistance-associated variants (RAVs) is not recommended except in specific situations:

• For persons with HCV genotype 1a being considered for treatment with simeprevir with PEG-IFN and ribavirin
• For persons with HCV genotype 1 previously treated with an NS5A inhibitor who are being considered for retreatment 1

Coinfection Screening

While not explicitly mentioned in the HCV guidelines, screening for coinfections is standard practice in infectious disease management. Based on HIV management guidelines, which often apply to HCV patients due to similar risk factors, consider:

• Hepatitis B surface antigen, surface antibody, and core antibody
• HIV antibody testing 2

Monitoring During Treatment

Once treatment is initiated, follow-up testing should include:

• Complete blood count, creatinine level, calculated GFR, and hepatic function panel after 4 weeks of treatment and as clinically indicated 1
• Regular clinic visits or telephone contacts as clinically indicated to ensure medication adherence and monitor for adverse events

Common Pitfalls to Avoid

1. Inadequate baseline assessment: Failing to obtain complete baseline labs may lead to missing contraindications to specific treatments.

2. Overlooking drug interactions: HCV medications have numerous potential drug interactions that can affect efficacy and safety.

3. Improper timing: Laboratory tests should be performed within the recommended timeframe (within 12 weeks prior to starting therapy) to ensure results accurately reflect the patient's current status.

4. Neglecting resistance testing in specific populations: While routine resistance testing isn't needed for most patients, it's essential for certain populations as noted above.

5. Forgetting to assess renal function: Many HCV medications require dose adjustments or are contraindicated in patients with renal impairment.

By following these evidence-based recommendations for pre-treatment laboratory testing, clinicians can optimize treatment selection, minimize adverse events, and improve outcomes for patients with HCV infection.