Comparison of dried blood spots and venous blood for the detection of SARS-CoV-2 antibodies in a population of nursing home residents

Abstract

In the current SARS-CoV-2 pandemic, testing for SARS-CoV-2 specific antibodies is paramount to monitor immune responses in post-authorization vaccination and sero-epidemiology studies. However, large scale and iterative serological testing by venipuncture in older persons can be challenging. Capillary blood sampled using a finger prick and collected on protein saver cards, i.e. dried blood spots (DBS), has already proven to be a promising alternative. However, elderly persons have a reduced cutaneous microvasculature, which may affect DBS-based antibody testing. Therefore, we aimed to evaluate the performance of DBS for the detection of SARS-CoV-2 antibodies in nursing homes residents. We collected venous blood and paired Whatman and EUROIMMUN DBS from nursing home residents, and from staff as a reference population. Venous blood samples were analyzed for the presence of SARS-CoV-2 IgG antibodies using the Abbot chemiluminescent microparticle immunoassay (CMIA). DBS were analyzed by the EUROIMMUN enzyme-linked immuno sorbent assay (ELISA) for SARS-CoV-2 IgG antibodies. We performed a statistical assessment to optimize the ELISA cut-off value for the DBS using the Youden's J index. A total of 273 paired DBS-serum samples were analyzed, of which 129 were positive as assessed by the reference test. The sensitivities and specificities of DBS ranged from 95% to 97.1% and from 97.1% to 98.8%, respectively, depending on population (residents or staff) or DBS card type. These results demonstrate that DBS sampling is a valid alternative to venepuncture for the detection of SARS-CoV-2 antibodies in the elderly.

Pre-vaccination SARS-CoV-2 seroprevalence among staff and residents of nursing homes in Flanders (Belgium) in fall 2020

“…To assess the presence of SARS-CoV-2-specific IgG antibodies, capillary blood was collected via a finger prick from each participant on protein saver cards and air-dried (i.e., dried blood spots, DBS) as previously described [13]. A pilot study showed that the sensitivities and specificities of DBS were at least 95% and 97%, respectively, depending on population (residents or staff) or DBS card type [13].…”

“…To assess the presence of SARS-CoV-2-specific IgG antibodies, capillary blood was collected via a finger prick from each participant on protein saver cards and air-dried (i.e., dried blood spots, DBS) as previously described [13]. A pilot study showed that the sensitivities and specificities of DBS were at least 95% and 97%, respectively, depending on population (residents or staff) or DBS card type [13]. DBS were sent to the Laboratory Bacteriology Research (LBR, Department Diagnostic Sciences, Faculty of Medicine and Health Sciences, Ghent University) and stored at four °C in an airtight container of low humidity and analysed within a period of 5 days.…”

“…A second remark is that previous papers show that, in estimating prevalences of rare diseases, the uncertainty in the sensitivity and specificity of the used test, may result in an underestimation of the prevalence [40]. Therefore, we additionally adjusted our global prevalence by applying Bayesian inference analysis, using the data obtained in the pilot validation study [13] as…”

“…DBS were sent to the Laboratory Bacteriology Research (LBR, Department Diagnostic Sciences, Faculty of Medicine and Health Sciences, Ghent University) and stored at four °C in an airtight container of low humidity and analysed within a period of five days. The DBS were analysed for the presence of anti-spike (anti-S) IgG antibodies by means of ELISA (EUROIMMUN, PerkinElmer Health Sciences Inc., Lübeck, Germany) as described previously [13]. Participants were classified as seronegative or seropositive according to the antibody optical density results of the ELISA (<0.8 or ≥0.8 respectively).…”

“…Therefore, we additionally adjusted our global prevalence by applying Bayesian inference analysis, using the data obtained in the pilot validation study [13] as prior data. This resulted in an adjusted https://www.cambridge.org/core/terms.…”