Long‐term stability and reproducibility of frozen plasma control samples for hepatitis B virus, hepatitis C virus, and human immunodeficiency virus by quantitative PCR : Implications for retrospective testing in hemovigilance

Abstract Objective Data on the long‐term stability and reproducibility of nucleic acid amplification testing (NAT) results in frozen stored positive samples (≤−20°C) remain limited. This study evaluated the long‐term performance of frozen virus‐positive samples in quantitative PCR assays and aimed to provide evidence for their analytical reliability in retrospective NAT and quality assurance. Because blood transfusions, despite their high safety, still carry a residual risk of transmission of blood‐borne viruses, these data may also be relevant for look‐back investigations in hemovigilance. Materials and Methods Diluted and aliquoted internal run controls from positive patient samples were retrospectively analyzed using routine quantitative PCR assays. Long‐term stability was assessed over 37 months for HIV, 25 and 29 months for HBV‐A and HBV‐B, and 49 and 38 months for HCV‐A and HCV‐B. Descriptive statistics and linear regression were used to assess variability and temporal trends. Compliance with the German Medical Association's guidelines for quality assurance in medical laboratory testing (Rili‐BAEK) was evaluated using an acceptance range of ±0.5 log10. Results All internal run controls demonstrated stable long‐term performance during frozen storage and routine use. Across the datasets, 99.2%–100% of measurements remained within the acceptance range. Results outside mean ± 3 SD were rare, and no statistically significant temporal trend was observed for any internal run control. Conclusion Frozen HBV‐, HCV‐, and HIV‐positive samples showed robust long‐term stability and reproducibility in routine quantitative PCR assays for up to 4 years. These findings support the suitability of long‐term stored specimens for retrospective NAT.