Nucleic acid testing for monkeypox in United States blood donor specimens

The 2022 multi-country outbreak of monkeypox (mpox) resulted in blood collection and public health agencies closely monitoring for changes in transmission dynamics that could pose a threat to the blood supply. While mpox virus (MPXV) is not known to be transfusion transmissible, there have been several studies demonstrating the detection of MPXV in blood. We evaluated the performance characteristics of a research use only (RUO) nucleic acid amplification test for MPXV. The assay was developed to detect MPXV DNA in plasma and serum specimens from human blood donors. The sensitivity of the RUO MPXV Assay was determined using a synthetic DNA sequence, purified full-length genomic DNA, and a chemically inactivated virus. Specificity was determined using fresh plasma samples collected from blood donors during the outbreak. Plasma samples collected from donors considered at increased risk for exposure to mpox were also tested. For sensitivity, the 95% limit of detection (LOD) ranged from 0.26 copies/mL (inactivated virus) to 31.65 copies/mL (synthetic DNA) to 166.61 copies/mL (for full-length DNA). All donor samples tested with the RUO MPXV Assay were nonreactive, resulting in a specificity of 100% (95% CI, 99.93%-100.00%). The RUO MPXV Assay was developed as a potential blood donation screening assay in response to the outbreak. While not directly comparable, the 95% LOD fiducial limits obtained from partial- and full-length DNA analysis were similar to other manufacturers' MPXV assays. Additionally, this assay demonstrated high specificity for screening blood donors.