Validation of a SARS-CoV-2 RNA RT-PCR assay for high-throughput testing in blood of COVID-19 convalescent plasma donors and patients.

Strasser, E F; Steininger, P A; Korn, K; Achenbach, S; Tenbusch, M; Cunningham, S; Zimmermann, R; Ãœberla, K; Hackstein, H

BACKGROUND The frequency of SARS-CoV-2 RNAemia in blood donors is uncertain. Thus, assays for SARS-CoV-2 RNA detection in blood, validated on commercially available PCR systems, are required to allow a good comparability of data. MATERIAL AND METHODS The cobas SARS-CoV-2 dual-target RT-PCR assay, licensed for respiratory swab SARS-CoV-2 RNA testing, was validated for detection of viral RNA in blood. For the validation panel, SARS-CoV-2 positive plasma samples were prepared by spiking SARS-CoV-2 positive respiratory specimens in negative human plasma. The 95% limit of detection (LOD95) was determined by probit analysis. For clinical validation, COVID-19 convalescent plasma (CCP) donors and COVID-19 patients with a severe disease course treated in an intensive care unit (ICU) were included. RESULTS The validation of the SARS-CoV-2 RT-PCR assay for blood demonstrated high sensitivity, specificity, intra- and inter-assay precision and efficiency. The LOD95 for SARS-CoV-2 RNA was 5.0 genome copies/mL (95% CI, 3.3-12 copies/ml) for target 1 and 4.3 genome copies/mL (95% CI, 2.9-10 copies/ml) for target 2. In a cohort of 39 CCP donors with 66 CCP donations no SARS-CoV-2 RNA in plasma was detected. Screening of 25 blood samples of 19 ICU COVID-19 patients showed six positive results for SARS-CoV-2 RNA in at least one target of the assay. CONCLUSION The SARS-CoV-2 RNA assay, only licensed for respiratory swabs, performed on a PCR system for high-throughput testing, showed a good assay performance for blood testing.