Medical Director LATAM Scientific Affairs, Abbott Transfusion Medicine Bogotá, Distrito Capital de Bogota, Colombia
Background/Case Studies: False-positive results in infectious disease screening represent a significant challenge in transfusion medicine. They can lead to unnecessary donor deferrals, increased confirmatory testing, and the potential loss of safe blood units. These outcomes affect blood availability, increase operational costs, and may cause emotional distress for donors. This study aimed to evaluate the impact of targeted interventions on the rate of presumed false-positive results for key infectious markers over a four-year period, with a particular focus on the pre-analytical phase.
Study
Design/Methods: A longitudinal observational study was conducted from 2021 to 2024 in a major blood bank in Bogotá, Colombia. The analysis included serological screening results for HIV, HBsAg, HCV, HTLV, Chagas, anti-HBc and Syphilis using the Alinity i instrument (Abbott). The window for observing the cleaning or culling effect had already passed and the proportion of first time and repeat donors were equivalent during the time frame of the study. For HIV, HBsAg, HCV, HTLV and Chagas, presumed false-positive rates were calculated based on repeat reactivity followed by negative confirmatory results, following national algorithms. For markers without confirmatory testing such as anti-HBc and Syphilis, trends in reactive rates were used as a proxy. Throughout the study period, a series of interventions were implemented to improve pre-analytical processes, including enhanced staff training, stricter sample handling protocols, and improved environmental controls (e.g. quality of water).
Results/Findings: A consistent and progressive decline in presumed false-positive rates was observed across all markers. HIV false-reactive rates decreased from 0.09% in 2021 to 0.05% (p< 0.05) in 2024. HBsAg dropped from 0.15% to 0.13%, and HCV from 0.58% to 0.34% over the same period. HTLV and Chagas also showed downward trends, although with greater year-to-year variability. Anti-HBc reactivity decreased from 0.85% in 2021 to 0.52% (p< 0.05) and Syphilis decreased from 1.35% to 1.16% over the same period. These improvements coincided with the timeline of implemented interventions, suggesting a strong association between pre-analytical quality and assay specificity.
Conclusions: Our findings underscore the critical role of pre-analytical phase optimization in enhancing the performance of infectious serology screening. Systematic improvements in this phase can significantly reduce false-positive results, contributing to safer, more efficient blood banking practices. These results support the integration of continuous quality improvement strategies focused on pre-analytical variables as a core component of transfusion safety programs.
