Emerg Infect Dis. 2024 Aug;30(8):1621-1630. doi: 10.3201/eid3008.240659. Epub 2024 Jul 9.
Nucleocapsid antibody assays can be used to estimate SARS-CoV-2 infection prevalence in regions implementing spike-based COVID-19 vaccines. However, poor sensitivity of nucleocapsid antibody assays in detecting infection after vaccination has been reported. We derived a lower cutoff for identifying previous infections in a large blood donor cohort (N = 142,599) by using the Ortho VITROS Anti-SARS-CoV-2 Total-N Antibody assay, improving sensitivity while maintaining specificity >98%. We validated sensitivity in samples donated after self-reported swab-confirmed infections diagnoses. Sensitivity for first infections in unvaccinated donors was 98.1% (95% CI 98.0-98.2) and for infection after vaccination was 95.6% (95% CI 95.6-95.7) based on the standard cutoff. Regression analysis showed sensitivity was reduced in the Delta compared with Omicron period, in older donors, in asymptomatic infections, <30 days after infection, and for infection after vaccination. The standard Ortho N antibody threshold demonstrated good sensitivity, which was modestly improved with the revised cutoff.
核衣壳抗体检测可用于估计在实施基于刺突蛋白的 COVID-19 疫苗的地区的 SARS-CoV-2 感染流行率。然而，据报道，核衣壳抗体检测在接种疫苗后检测感染的灵敏度较差。我们通过使用 Ortho VITROS Anti-SARS-CoV-2 Total-N 抗体检测，在一个大型献血者队列（N=142599）中确定了一个较低的截定点来识别以前的感染，在保持特异性>98%的同时提高了灵敏度。我们在自我报告的拭子确诊感染诊断后捐赠的样本中验证了敏感性。根据标准截定点，未接种疫苗的供体中首次感染的灵敏度为 98.1%（95%CI 98.0-98.2），接种疫苗后的感染灵敏度为 95.6%（95%CI 95.6-95.7）。回归分析显示，与奥密克戎时期相比，德尔塔变体时期的敏感性降低，在老年供体、无症状感染、感染后<30 天以及接种疫苗后感染时，敏感性降低。标准 Ortho N 抗体阈值显示出良好的灵敏度，使用修订后的截定点略有提高。
