DSI-NRF Centre of Excellence for Biomedical Tuberculosis Research, South African Medical Research Council Centre for Tuberculosis Research, Department of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town, South Africa.
Division of Clinical Pharmacology, Department of Medicine, Stellenbosch University and Tygerberg Academic Hospital, Cape Town, South Africa.
PLoS One. 2021 Feb 25;16(2):e0247852. doi: 10.1371/journal.pone.0247852. eCollection 2021.
Inequality is rife throughout South Africa. The first wave of COVID-19 may have affected people in lower socioeconomic groups worse than the affluent. The SARS-CoV-2 seroprevalence and the specificity of anti-SARS-CoV-2 antibody tests in South Africa is not known.
We tested 405 volunteers representing all socioeconomic strata from the workforce of a popular shopping and tourist complex in central Cape Town with the Abbott SARS-CoV-2 IgG assay. We assessed the association between antibody positivity and COVID-19 symptom status, medical history, and sociodemographic variables. We tested 137 serum samples from healthy controls collected in Cape Town prior to the COVID-19 pandemic, to confirm the specificity of the assay in the local population.
Of the 405 volunteers tested one month after the first peak of the epidemic in Cape Town, 96(23.7%) were SARS-CoV-2 IgG positive. Of those who tested positive, 46(47.9%) reported no symptoms of COVID-19 in the previous 6 months. Seropositivity was significantly associated with living in informal housing, residing in a subdistrict with low income-per household, and having a low-earning occupation. The specificity of the assay was 98.54%(95%CI 94.82%-99.82%) in the pre-COVID controls.
There is a high background seroprevalence in Cape Town, particularly in people of lower socioeconomic status. Almost half of cases are asymptomatic, and therefore undiagnosed by local testing strategies. These results cannot be explained by low assay specificity.
南非普遍存在不平等现象。第一波 COVID-19 疫情对社会经济地位较低的人群的影响可能比富裕人群更为严重。南非 SARS-CoV-2 血清流行率和抗 SARS-CoV-2 抗体检测的特异性尚不清楚。
我们使用 Abbott SARS-CoV-2 IgG 检测试剂盒，对来自开普敦市中心一个受欢迎的购物和旅游综合体的各社会经济阶层的 405 名志愿者进行了检测。我们评估了抗体阳性与 COVID-19 症状状况、病史和社会人口统计学变量之间的关联。我们检测了 137 份在 COVID-19 大流行前从开普敦采集的健康对照者的血清样本，以确认该检测在当地人群中的特异性。
在开普敦疫情第一波高峰后一个月检测的 405 名志愿者中，有 96 人（23.7%）SARS-CoV-2 IgG 阳性。在检测阳性者中，有 46 人（47.9%）在过去 6 个月内没有 COVID-19 症状。血清阳性与居住在非正规住房、居住在低收入家庭所在的分区以及从事低收入职业显著相关。在 COVID-19 前的对照组中，该检测的特异性为 98.54%（95%CI 94.82%-99.82%）。
开普敦存在较高的背景血清流行率，尤其是在社会经济地位较低的人群中。近一半的病例为无症状，因此未被当地检测策略检出。这些结果不能用低检测特异性来解释。
