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Background: In low‐risk populations, variability in the sensitivity of current serological tests for Hepatitis C virus (HCV) blood donor screening may lead to the presence of false‐positive results. This contributes to the unnecessary loss of blood donor samples as well as to difficulty in accurate donor counselling. The present study determined the optimal cut‐off value of a chemiluminescent immunoassay for identification of HCV‐reactive blood donors. Study Design and Methods: In a retrospective cross‐sectional analysis of 193 973 blood donations, 578 samples that were positive for HCV antibody in a chemiluminescent immunoassay and/or RNA screening tests were identified. Blood from 379 of these positive samples was available for retesting by a second confirmatory HCV immunoassay followed by a receiver operating characteristic (ROC) curve analysis. Donors were also recalled for a new analysis. Results: Only 71 (18.7%) blood samples remained HCV‐positive upon retesting, while 233 (61.5%) now tested negative and 75 (19.8%) yielding indeterminate results. A signal to cutoff ratio ≥4.32 was determined as the best differential threshold between a positive and negative result, increasing the positive predictive value from 27.3% to 66.7%. Conclusion: Using a higher threshold for an HCV‐positive blood sample enhances the chemiluminescent immunoassay screening test´s accuracy and helps to improve donor counselling and notification processes. [ABSTRACT FROM AUTHOR]