Real-time strand-specific quantitative assay for the detection of HCV RNA–negative and –positive strands in liver tissue. One microgram of total RNA was extracted from an infected liver and serially diluted in water; one μg of RNA extracted from uninfected liver was added to each dilution to keep the quantity of RNA constant. (A) Detection of HCV RNA–negative strand: sense primer present in the reverse transcription step. (B) Detection of HCV RNA–positive strand: negative-antisense primer present in the reverse transcription step.