[Screening of Hepatitis C virus in blood donors over 11 years].

Background: HCV infection remains a global concern due to its often asymptomatic course and the potential for transfusion transmission during the window period. In this setting, nucleic acid testing (NAT) can detect early viremia that is not yet identifiable by serology, thereby strengthening blood safety. Objective: To quantify HCV NAT yield (NAT-reactive donations with non-reactive anti-HCV serology, consistent with window-period detection) in blood donors using combined NAT and serology over an 11-year period. Material and methods: Cross-sectional, observational study including 568,569 donations recorded at the CMN Siglo XXI Blood Bank (2014-2025). NAT and serology results were analyzed in accordance with NOM-253-SSA1-2012 to identify donations with a NAT-reactive/serology-non-reactive pattern. Results: One NAT-reactive/serology-non-reactive case was identified, consistent with window-period infection. The NAT yield rate was 0.18 per 100,000 donations (1.8 per million). No risk factors or coinfections were reported, indicating that serology alone would have missed the infection. Because only one case was documented over 11 years, population-level inferences and epidemiologic impact estimates are not supported. Conclusions: In a large cohort within a very low-frequency setting, NAT identified a potentially infectious donation that serology did not detect. Although the absolute yield was low, each detected case is relevant to transfusion safety. Expanding NAT coverage and strengthening voluntary donation are recommended to optimize transfusion safety in Mexico.