[Diagnosis of type C chronic hepatitis using PCR technology]

Many studies have suggested that examination of a patient's serum for viral RNA by reverse transcriptase-polymerase chain reaction (RT-PCR) is the most sensitive and specific serological means of determining chronic HCV infection. Moreover, technique to quantify HCV RNA in serum using PCR technology has been developed, and diagnosis of HCV genotype by PCR with mixed primers has been used for diagnosis of type C hepatitis. Herein, we discuss the laboratory technique and significance of various PCR methods. HCV RNA can be detected by amplification technique of RT-PCR. Primers in the 5'-noncoding region are frequently used to detect HCV RNA, because the RNA sequence in this region is the most conserved. We usually perform 30 cycles of amplification with outer primers and another 30 cycles with inner primers (nested RT-PCR). Using this technique, HCV RNA was detected in 96% of anti-HCV-positive chronic hepatitis patients. This PCR technique gives us important information for the diagnosis of type C chronic hepatitis indicating HCV infection. The competitive PCR technique is usually used to quantify HCV RNA. This method is based on complification of the target RNA with known amounts of synthetic mutant RNA. The mutant RNA should be amplified by the same primers for amplifying target RNA, and should be distinguished from target RNA by the size of the amplified DNA product by making a deletion or restriction site artificially. Quantifying HCV RNA before interferon therapy is useful to predict the effectiveness of the therapy; patients with a large amount of HCV RNA tend to have a poor outcome.(ABSTRACT TRUNCATED AT 250 WORDS)