We investigated the performance of dried blood spots (DBS) in hepatitis C virus (HCV) diagnosis using modified commercial tests. Paired DBS and serum samples were collected from 200 patients: 100 patients with anti-HCV antibodies (anti-HCV), including 62 patients with detectable serum HCV RNA, and 100 patients without anti-HCV. The DBS sample consisted of three drops of approximately 50 L of whole blood applied to a paper card, which was then stored at ؊20°C within 48 hours of collection. Using the Ortho HCV 3.0 enzyme-linked immunosorbent assay kit on DBS, we observed both a specificity and sensitivity of 99% in detecting anti-HCV. HCV RNA was detected on DBS in 60/62 (97%) patients with detectable serum HCV RNA, which was then successfully quantified in 55 samples (89%) using the Cobas TaqMan HCV test. A good correlation was observed between the DBS HCV RNA concentration and the serum level (r 2 ؍ 0.95; P < 0.001). HCV genotyping was successfully performed on DBS samples, with a full concordance between the 14 paired DBS and serum samples (genotypes 1-4). Conclusion: This study presents DBS as a reliable alternative to serum specimens for detecting anti-HCV, quantifying HCV RNA and genotyping HCV. DBS may increase the opportunities for HCV testing and treatment follow-up in hard-to-reach individuals. (HEPATOLOGY 2010;51:752-758.) H epatitis C virus (HCV) infection is currently underdiagnosed, leaving many individuals unaware of their infection status. Some population groups, such as sex workers, the homeless, prisoners, or other institutionalized individuals, have a higher prevalence of HCV infection than the general population. [1][2][3] However, HCV testing in these groups is limited by the poor acceptability or feasibility of venipuncture. Collecting capillary blood spots on filter paper requires less staff training, is less invasive, involves smaller blood volumes, and is ideal for high-risk patients with damaged veins, such as intravenous drug users. 4 In addition, this technique can reduce the cost of HCV testing by simplifying sample collection, processing (no centrifugation), storage, and shipment. Many studies have already demonstrated the value of dried blood spots (DBS) for the serological and molecular diagnosis of human immunodeficiency virus. [5][6][7][8][9][10][11] Routine screening for HCV infection relies on detecting antibodies against HCV (anti-HCV) using highly sensitive second-or third-generation enzyme immunoassay. DBS have been used to detect anti-HCV among intravenous drug users, prisoners and childbearing women. 12-17 However, the diagnosis of acute or chronic infection also requires the detection of HCV RNA by polymerase chain reaction (PCR). 18,19 Likewise, when recent HCV infection is suspected or the patient is immunocompromised, then the sample should be referred for PCR. Samples with a low screening signal-to-cutoff ratio may also need confirmation with these more specific recombinant immunoblot assays. 20,21 In this study, we have investigated both anti-HCV and HCV RNA detecti...