False-positive infectious screening results among blood donors

High-sensitivity assays for infectious screening of blood donations still occasionally result in false-positive test results (FPTRs). The cause of FPTRs is not always clear and may stem from both lot-dependent and lot-independent factors. FPTRs generate additional administration and extra costs for confirmatory testing and may cause concern among deferred donors.

First-time and second-time FPTRs among blood donors screened from January 2021 to November 2023 were identified in the blood bank computer system. Abbott Alinity i hepatitis B surface antigen, hepatitis C virus (HCV) antibody and human immunodeficiency virus (HIV) antibody/antigen assays and Roche Cobas MPX assay were used for screening. Using logistic regression, we examined whether the risk of second-time FPTR was affected by being a new donor, sex, age and time between two donations.

During the study period, 38,962 donors gave 223,323 donations. The total number of FPTRs was 216. Among the donors with a first-time FPTR, 83 had a second donation within the observation period, and 56 (67.5%) of these had a second-time FPTR. In total, 0.2% of donors were deferred because of second-time FPTR. New donors with a first-time FPTR had a significantly higher risk (adjusted odds ratio [aOR] = 6.06, 95% confidence interval [CI] [1.17-31.55]) of a second-time FPTR, which occurred in 89.5% of cases.

An increased risk of second-time FPTR was found among new donors, and hence it may be beneficial considering the donors' ethical and economical aspects, to defer this group of donors after the initial FPTR. Lot-independent factors might explain why some donors keep getting FPTR even after years.