II. Course of Anti-HCV Antibody
- Present in up to 70% at onset of symptoms
- Present in 90% of cases at 3 months
- Present in most cases by 6 months post-exposure
III. Screening Tests
-
ELISA-1 (replaced by ELISA-2)
- Detects seroconversion 15-20 weeks after exposure
- Sensitivity: 81-89%
- Specificity: Poor (High rate of False Positives)
-
ELISA-2 (preferred Screening Test)
- First line test
- Detects seroconversion 1-6 weeks after exposure
- Efficacy improved over ELISA-1
- Test Sensitivity: 99%
- Test Specificity: 99%
- False Negative tests if Immunocompromised
IV. Confirmatory Tests
- RIBA-2 (replaced by RT-PCR for confirmation)
- Indication: confirm Elisa-2 (RT-PCR preferred)
- Small advantage over ELISA-2
- Reverse transcriptase PCR for HCV RNA (RT-PCR)
- Indication: RIBA is indeterminate
- Best available diagnostic test
- Sensitivity: High
- Detects very low serum and tissue levels
- Qualitative test detects HCV to 5-50 copies/ml
- Specificity: High
- Disadvantages
- Expensive
- Requires flawless technique for accurate results