Hepatitis C virus RNA assays - A comparison of SuperQuant and Monitor

Hepatitis C RNA testing has been used extensively to assess the efficacy of antiviral therapy and has increasingly become an integral part of clinical management of patients with chronic hepatitis C. A variety of commercially available hepatitis C virus (HCV) RNA tests are used to detect HCV RNA qua litatively or quantitatively. These commercial tests have fundamental diffe rences that are reflected on the values they generate. We compared two wide ly used assays, HCV SuperQuant (SQ) and Amplicor HCV Monitor (M1 and M2), i n sera of patients with chronic hepatitis C. A total of 506 sera from 79 pa tients were tested with both assays. The data were logarithmically transfor med and analyzed by linear regression and measurement of agreement. Two hun dred thirty-eight sera had HCV RNA values within the dynamic range of both assays. The correlation between the assays was fair, with a correlation coe fficient (r) of 0.699. Overall, SQ generated higher values than M1 with a m ean difference of 0.558 log (SD = 0.624). One hundred ninety-four (38%) and 121 (24%) of the sera were below the dynamic range of M1 and SQ, respectiv ely. Seventy-three sera, undetectable by M1, were positive by SQ. The Ampli cor HCV Monitor 2.0 (M2) was performed in 66 sera. All were positive by SQ and M2, but only 38 were within the dynamic range of M1. The correlations b etween these tests were good (r = 0.68-0.78), but the agreement was rather poor. In conclusion, this study confirms that both SQ and M2 are more sensi tive than M1. Additionally, our results show rather poor agreements between these assays. The recent attempts in standardizing the reporting of these assays should make their results more easily interchangeable.