2% overall, 13.4% among those in the baby boomer cohort, 2.7% among persons born since 1965, and 22.4% among those born before 1945. Conclusion Preliminary analyses of laboratory testing data indicate an increase in HCV antibody testing among persons in the ‘baby boomer cohort’, but a decline in the number newly identified as positive. The results demonstrate the feasibility of monitoring commercial laboratory data to assess the impact of the guidelines on HCV testing. Monthly average number of persons tested and testing positive, by year of birth, before

and after PXD101 chemical structure publication of guidelines Excludes persons missing ID or year of birth. Disclosures: Xiaohua Huang – Employment: Quest Diagnostics Anthony E. Yeo – Employment: Quest Diagnostics Mouneer Odeh – Employment: Quest Diagnostics; Stock Shareholder: Quest Diagnostics The following people have nothing to disclose: Monina Klevens, Daulati Thakare, John W. Ward Background: Understanding the patterns of HCV-RNA levels during acute HCV infection provides insights into immunopathogenesis and is important for vaccine design. This study assessed patterns of HCV-RNA levels and associated factors during acute HCV. Methods: Data were drawn from an international collaboration of nine prospective cohorts of acute HCV (InC3 Study). Individuals with well-characterized acute HCV (detected within 3 months

post-infection and Protease Inhibitor Library screening interval between the peak and subsequent HCV-RNA≤120 days) were categorised based on a priori-defined until patterns of HCV-RNA levels: i) spontaneous clearance, ii) partial viral control with persistence (≥1 log IU/mL decline in HCV-RNA levels following peak) and iii) viral plateau with persistence (increase or <1 log IU/mL decline in HCV-RNA levels following

peak). Results: Among 643 individuals with acute HCV, 162 with well-characterized acute HCV were identified. Spontaneous clearance, partial viral control with persistence, and viral plateau with persistence were observed in 52 (32%), 44 (27%), and 66 (41%) individuals, respectively (Figure). HCV-RNA levels reached a high viraemic phase one month following infection, with higher levels in spontaneous clearance and partial viral control with persistence groups, compared to viral plateau with persistence group (median: 6.0, 6.2, 5.3 log IU/mL; P=0.018). In two groups with persistence, interferon lambda 3 (IFNL3) CC genotype was independently associated with partial viral control compared to viral plateau (adjusted odds ratio [AOR]: 2.75; 95%CI: 1.08, 7.02). In two groups with viral control, female sex was independently associated with spontaneous clearance compared to partial viral control with persistence (AOR: 2.86; 95%CI: 1.04, 7.83). Conclusion: A spectrum of HCV-RNA patterns is evident in individuals with acute HCV. IFNL3 CC genotype is associated with initial viral control, while female sex is associated with ultimate spontaneous clearance. Disclosures: Arthur Y.