Rapid and accurate quantification of different HCV genotypes by LightCycler Real Time PCR and direct sequencing of HCV amplicons.

Follow-up of chronically infected HCV patients is the primary clinical goal in therapy administration. In the absence of an HCV vaccine, the timely monitoring of HCV viral load combined with the information of the viral genotype could contribute to patient disease management. A LightCycler Real Time RT-PCR assay was developed and optimized allowing rapid and accurate quantification of HCV RNA over an extended dynamic range using a single human reference standard. A total of 5,096 plasma samples, collected over almost 5 years, were tested and HCV RNA was quantified in 2,435 samples with levels ranging from 5.7x10(1) to 2.52x10(9) IU/ml. The precision and reproducibility of the test are documented by various inter-assay parameters of the reference standard obtained in 409 RT-PCR runs. This Real Time RT-PCR protocol uses the LightCycler cDNA amplicons for direct sequence analysis and reduces the sequencing time to approximately 3 hours. Nearly all HCV genotypes were identified. Viral sequences showed a similarity level close to 100%, independently from the viral load, while the LightCycler melting temperature analysis did not correlate with HCV genotypes. All this makes the LightCycler Real Time RT-PCR protocol a suitable tool for the diagnosis and monitoring of HCV infections.