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.

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.