Minipool testing for SARS‐CoV‐2 RNA in United States blood donors

Abstract

Background SARS‐CoV‐2 RNA prevalence in blood donors from large geographic areas of high community transmission is limited. We tested residual donor plasma minipools (MPs) to determine SARS‐CoV‐2 RNAemia prevalence in six United States areas. Study Design/Methods Blood donations collected from 7 March 2020 to 25 September 2020 were tested for SARS‐CoV‐2 RNA (vRNA) in MP of 6 or 16 donations using the Grifols Procleix SARS‐CoV‐2 research‐use only (RUO) transcription‐mediated amplification (TMA) assay. Reactive results were confirmed using an alternate target region TMA assay. Reactive MPs were tested by TMA after serial dilution to estimate viral load. Testing for anti‐SARS‐CoV‐2 antibodies and infectivity was performed. Results A total of 17,995 MPs corresponding to approximately 258,000 donations were tested for vRNA. Three confirmed reactive MP16 were identified. The estimated prevalence of vRNA reactive donations was 1.16/100,000 (95% CI 0.40, 3.42). The vRNA‐reactive samples were non‐reactive for antibody, and the estimated viral loads of the (presumed single) positive donations within each MP ranged from <1000 to <4000 copies/ml. When tested, no infectivity was observed in inoculated permissive cell cultures. Discussion Blood donation MP‐nucleic acid testing (NAT) indicated that SARS‐CoV‐2 RNAemia is infrequent and, when detected, the vRNA was at low concentrations. Only one RNA‐reactive MP could be tested for infectivity for operational reasons and was not infectious in cell culture. These findings support current recommendations from international and national regulatory agencies to not screen donors by NAT.

Low rate of RNAemia in blood donations collected during the first wave of COVID‐19 in France

“…Only one out of 9672 donations tested positive, which indicates 1.03 positive per 10,000 donations. Our findings are consistent with published data 2,20–23 reporting low prevalence rates, ranging from 0% in 98,342 blood donors tested prospectively in MP8 in China 22 to 0.3% in 690 blood donors tested individually in Pakistan 24 . The study reporting the largest number of tested donations was conducted in the United States.…”

“…The only reactive donation found here had a viral load close to the limit of detection of the methods used for both screening and confirmation. This is consistent with the RNA loads in blood donations estimated by Bakkour et al (from <1000 to <4000 copies/ml) 21 but also with data obtained in symptomatic individuals (60-6000 copies/ml). 7 In our study, the donor tested positive in plasma was asymptomatic and antibody-negative at the time of donation and reported COVID-19-related symptoms after blood donation at the post-donation interview when the donor was recalled for information.…”

“…Out of approximately 258,000 donations tested in pools of 6 or 16 donations collected from March to September 2020 in 6 metropolitan areas, only three tested positive, resulting in a prevalence rate 10 times lower than in our study (1.16 per 100,000 donations). 21 Differences in prevalence according to studies may be linked to the sensitivity level of the NAT method, especially if based on MP since this may have further diluted the already low levels of RNA present in plasma, generating potentially false-negative samples. The number of samples tested, the study period, and the geographic study areas may also impact results.…”

“…However, to date, there is no evidence of viral transmission through blood, and viral infectivity has not been demonstrated in viral culture. 7,21 No clinical consequences have come to light in patients transfused with RNA-reactive blood components and SARS-CoV-2 is highly sensitive to inactivation procedures. This also mitigates the risk of transmission through blood components to which the process is applied.…”

“…Secondly, although uncommon in infected donors, viral sequences can be detected in the plasma of asymptomatic donors. However, to date, there is no evidence of viral transmission through blood, and viral infectivity has not been demonstrated in viral culture 7,21 . No clinical consequences have come to light in patients transfused with RNA‐reactive blood components and SARS‐CoV‐2 is highly sensitive to inactivation procedures.…”