PROJECT SUMMARY Infection due to Hepatitis C virus (HCV) is a current global health burden and is estimated that globally more than 58 million people have chronic HCV with about 1.5 million new infections occurring per year. If left untreated HCV infection can lead to cirrhosis and hepatocellular carcinoma. Despite significant recent advances in the development of highly effective and affordable HCV treatment, one of the major challenges in HCV infection management is rapid and early diagnosis of active HCV infection particularly those in resource- limited settings. Worldwide, only 21% of HCV-infected people are diagnosed. Of particular interest are the American Indians and Alaska Natives (AI/AN) who are disproportionally affected with new HCV infection rate of 2.9 cases/100,000 as compared to 0.5 cases/100,000 in African Americans and 1.2 cases/100,000 in non- Hispanic Whites with significantly higher mortality rates compared to non-AI/AN ethnic and racial groups. The two-step HCV testing process of HCV antibody testing followed by confirmatory HCV RNA testing is expensive, time-consuming, and suboptimal, which has led to significant drop out of HCV-infected individuals from the cascade of HCV management before receiving care. The HCV antibody testing cannot be used for detecting active infection due to its inability to distinguish between resolved HCV (R-HCV) and viremic HCV (V- HCV). The currently available HCV RNA testing assays including the POC HCV RNA assays are still lab-based and expensive and may not be available in most resource-limited settings and those with HCV-related health disparities including AIs/ANs. Low-cost, rapid, sensitive, and specific POC HCV antigen testing is an attractive alternative approach that holds great promise for one-step HCV screening and diagnosis. There is currently no commercially available and FDA-approved POC HCV Ag testing device. The already developed HCV Ag assays are lab-based, relatively expensive, and more importantly not sensitive/specific enough particularly when tested with samples with clinically relevant low viral loads (<1000 IU/mL), which has limited their clinical utilities. The Abbott Architect HCVcAg assay had a sensitivity of 64.7%-81.9% when tested with HCV serum samples with <104 IU/mL viral loads and 0.0%-19.7% when tested with HCV serum samples with <1000 IU/mL viral loads. Therefore, to increase access to HCV care particularly those disproportionally affected such as AIs/ANs, there is an urgent need for inexpensive, rapid, sensitive, and specific POC HCV Ag diagnostic testing. The main goal of this interdisciplinary project is developing a smartphone-based diagnostic system for rapid (<30 minutes) and sensitive (LoD of 200 IU/mL to 1000 IU/mL) HCV detection using fingerprick volume (<100 µL) of a whole blood sample placed on an inexpensive (<$2 material cost), disposable, and mass- producible microfluidic-based cartridge. We will validate the proposed device with HCV-infected patien...