Mekelle University College of Health Sciences, Mekelle, Ethiopia.
Ethiopian Public Health Institute, Addis Ababa, Ethiopia.
PLoS One. 2022 Mar 23;17(3):e0263627. doi: 10.1371/journal.pone.0263627. eCollection 2022.
Serological testing for SARS-CoV-2 plays an important role for epidemiological studies, in aiding the diagnosis of COVID-19, and assess vaccine responses. Little is known on dynamics of SARS-CoV-2 serology in African settings. Here, we aimed to characterize the longitudinal antibody response profile to SARS-CoV-2 in Ethiopia.
In this prospective study, a total of 102 PCR-confirmed COVID-19 patients were enrolled. We obtained 802 plasma samples collected serially. SARS-CoV-2 antibodies were determined using four lateral flow immune-assays (LFIAs), and an electrochemiluminescent immunoassay. We determined longitudinal antibody response to SARS-CoV-2 as well as seroconversion dynamics.
Serological positivity rate ranged between 12%-91%, depending on timing after symptom onset. There was no difference in positivity rate between severe and non-severe COVID-19 cases. The specificity ranged between 90%-97%. Agreement between different assays ranged between 84%-92%. The estimated positive predictive value (PPV) for IgM or IgG in a scenario with seroprevalence at 5% varies from 33% to 58%. Nonetheless, when the population seroprevalence increases to 25% and 50%, there is a corresponding increases in the estimated PPVs. The estimated negative-predictive value (NPV) in a low seroprevalence scenario (5%) is high (>99%). However, the estimated NPV in a high seroprevalence scenario (50%) for IgM or IgG is reduced significantly to 80% to 85%. Overall, 28/102 (27.5%) seroconverted by one or more assays tested, within a median time of 11 (IQR: 9-15) days post symptom onset. The median seroconversion time among symptomatic cases tended to be shorter when compared to asymptomatic patients [9 (IQR: 6-11) vs. 15 (IQR: 13-21) days; p = 0.002]. Overall, seroconversion reached 100% 5.5 weeks after the onset of symptoms. Notably, of the remaining 74 COVID-19 patients included in the cohort, 64 (62.8%) were positive for antibody at the time of enrollment, and 10 (9.8%) patients failed to mount a detectable antibody response by any of the assays tested during follow-up.
Longitudinal assessment of antibody response in African COVID-19 patients revealed heterogeneous responses. This underscores the need for a comprehensive evaluation of seroassays before implementation. Factors associated with failure to seroconvert needs further research.
血清学检测在流行病学研究、辅助 COVID-19 诊断和评估疫苗反应方面发挥着重要作用。在非洲环境中，人们对 SARS-CoV-2 血清学的动态变化知之甚少。在此，我们旨在描述埃塞俄比亚 SARS-CoV-2 血清学的纵向抗体反应特征。
在这项前瞻性研究中，共纳入了 102 例经 PCR 确诊的 COVID-19 患者。我们获得了 802 份连续采集的血浆样本。使用四种侧向流动免疫分析（LFIAs）和电化学发光免疫分析来确定 SARS-CoV-2 抗体。我们确定了 SARS-CoV-2 的纵向抗体反应以及血清转换动态。
血清学阳性率在 12%-91%之间，具体取决于症状出现后的时间。严重和非严重 COVID-19 病例的阳性率无差异。特异性在 90%-97%之间。不同检测之间的一致性在 84%-92%之间。在血清流行率为 5%的情况下，IgM 或 IgG 的估计阳性预测值（PPV）范围为 33%至 58%。然而，当人群血清流行率增加到 25%和 50%时，估计的 PPV 会相应增加。在低血清流行率（5%）的情况下，估计的阴性预测值（NPV）很高（>99%）。然而，在高血清流行率（50%）的情况下，IgM 或 IgG 的估计 NPV 显著降低至 80%至 85%。总体而言，在中位时间为 11（IQR：9-15）天的症状发作后，28/102（27.5%）例通过一种或多种检测方法血清转换。与无症状患者相比，有症状患者的血清转换中位时间更短[9（IQR：6-11）天 vs. 15（IQR：13-21）天；p=0.002]。总体而言，症状发作后 5.5 周抗体血清转换达到 100%。值得注意的是，在纳入的队列中，74 例剩余 COVID-19 患者中有 64 例（62.8%）在入组时抗体呈阳性，10 例（9.8%）患者在随访期间通过任何检测均未能检测到可检测的抗体反应。
对非洲 COVID-19 患者的抗体反应进行纵向评估发现，其存在异质性反应。这凸显了在实施之前全面评估血清学检测的必要性。与未能血清转换相关的因素需要进一步研究。
