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We report the results of a multicenter evaluation of a new assay for the detection of hepatitis C virus (HCV) RNA in human serum or plasma based on transcription-mediated amplification (HCV TMA). Analysis of combined data obtained from 15 independent sites, including 4 sites in the United States and 11 in Europe, by using preproduction kits showed a limit of detection of 9.8 IU/ml and an overall mean specificity of 97.9%. In addition, assay runs and samples were valid consistently (97.8% of assay runs and 98.0% of specimen results). Of the 15 sites that participated in the multicenter evaluation, 2 subsequently carried out additional performance studies with production kits in support of the assay's registration in France. Comparison of the findings from these two sites during the multicenter evaluation and during the registration studies showed an overall improvement in assay performance. A statistically significant (P < 0.001) improvement was achieved for both specificity and specimen validity in the registration studies, which were 99.4 and 98.1%, respectively. Combined data from the two sites showed a lower limit of detection of approximately 2.4 IU/ml and an improved assay validity of 100%, although the sample size was too small to show statistical significance at the 0.05 level. In summary, the performance characteristics of HCV TMA indicate that this assay is a reliable tool for the detection of HCV RNA in serum or plasma. Improvement in assay performance has been demonstrated with refinement of assay reagents, instrumentation, and operator experience.Qualitative hepatitis C virus (HCV) RNA assays play a key role in both the diagnosis and monitoring of HCV infection. The enzyme immunoassays (EIAs) that detect antibodies to HCV cannot differentiate between active and resolved infection. Qualitative HCV RNA assays detect viral genomes and therefore can both confirm the presence of active infection and demonstrate its presence 4 to 6 weeks before antibody seroconversion takes place (1). Most qualitative HCV RNA tests are 10-to 100-fold more sensitive than are quantitative HCV RNA tests and up to 1,000-fold more sensitive than is the HCV core antigen assay, rendering them the method of choice both for confirming active infection and for assessing viral clearance in response to therapy (4, 7). Indeed, according to the recent National Institutes of Health consensus statement on management of hepatitis C (http://consensus.nih-gov/cons/116 /116cdc_intro.htm), a qualitative HCV RNA assay with a lower limit of detection of 50 IU/ml or less should be used to confirm acute or chronic HCV infection in a patient with a positive EIA result as well as to indicate sustained virologic response, defined as the absence of detectable HCV RNA in serum at 24 weeks after the end of treatment.A new assay for the detection of HCV RNA in human serum or plasma based on transcription-mediated amplification (HCV TMA) has recently been introduced. Developed and manufactured by Gen-Probe Inc. (San Diego, Calif.) and marketed by Bayer Co...

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