Use of whole blood specimens for routine clinical quantitation of hepatitis C virus RNA does not increase assay sensitivity.

The measurement of hepatitis C virus (HCV) RNA levels in the blood has, in the last few years, become a critical component in the therapy of patients with HCV infections. Initially, extraction methods for serum and plasma were used, but a newer method that uses Catrimox-14 as the extraction agent for whole blood has been reported. Because the whole blood extraction method may yield higher virus levels if significant levels of virus are present in the white blood cells (WBC), the method was evaluated for use in our clinical diagnostic laboratory despite its higher reagent costs and more time-consuming methodology. RNA was simultaneously extracted from 39 clinical samples by four different methods: Catrimox-14-Trizol extraction from whole blood, Trizol extraction from whole blood, Trizol extraction from serum, and a commercial serum extraction method, the EZNA total RNA kit. In addition, in an effort to quantitate the amount of HCV RNA virus in the WBC, Trizol extraction from isolated WBC was also performed. Quantitative results for samples from which RNA was extracted by all four methods were essentially the same; the Catrimox-14-Trizol method did not yield increased virus levels. Insignificant levels of virus were found in the WBC. The results did not demonstrate a clinical usefulness for the Catrimox-14-Trizol method.