Evaluation of serological assays for SARS-CoV-2 antibody testing from dried blood spots collected from cohorts with prior SARS-CoV-2 infection

High pre-Delta and early-Omicron SARS-CoV-2 seroprevalence detected in dried blood samples from Kinshasa (D.R. Congo)

Studies on the impact of the COVID-19 pandemic in sub-Saharan Africa have yielded varying results, although authors universally agree the real burden surpasses reported cases. The primary objective of this study was to determine SARS-CoV-2 seroprevalence among patients attending Monkole Hospital in Kinshasa (D.R. Congo). The secondary objective was to evaluate the analytic performance of two chemiluminescence platforms: Elecsys® (Roche) and VirClia® (Vircell) on dried blood spot samples (DBS). The study population (N = 373) was recruited in two stages: a mid-2021 blood donor cohort (15.5% women) and a mid-2022 women cohort. Crude global seroprevalence was 61% (53.9%-67.8%) pre-Delta in 2021 and 90.2% (84.7%-94.2%) post-Omicron in 2022. Anti-spike (S) antibody levels significantly increased from 53.1 (31.8-131.3) U/mL in 2021 to 436.5 (219.3-950.5) U/mL in 2022 and were significantly higher above 45 years old in the 2022 population. Both platforms showed good analytic performance on DBS samples: sensitivity was 96.8% for IgG (antiN/S) (93.9%-98.5%) and 96.0% (93.0%-98.0%) for anti-S quantification. These results provide additional support for the notion that exposure to SARS-CoV-2 is more widespread than indicated by case-based surveillance and will be able to guide the pandemic response and strategy moving forward. Likewise, this study contributes evidence to the reliability of DBS as a tool for serological testing and diagnosis in resource-limited settings.

Testing, diagnosis, and treatment following the implementation of a program to provide dried blood spot testing for HIV and hepatitis C infections: the NSW DBS Pilot

BACKGROUND

Dried blood spot (DBS) testing provides an alternative to phlebotomy and addresses barriers to accessing healthcare experienced by some key populations. Large-scale evaluations of DBS testing programs are needed to understand their feasibility. This study evaluated the implementation of a state-wide DBS HIV and hepatitis C virus (HCV) testing pilot.

METHODS

The New South Wales (NSW) DBS Pilot is an interventional cohort study of people testing for HIV antibody and/or HCV RNA from DBS samples in NSW, Australia. Participants at risk of HIV/HCV participated in testing via: 1) self-registration online with a DBS collection kit delivered and returned by conventional postal service; or 2) assisted DBS sample collection at 36 community health sites (including drug treatment and harm-minimisation services) and prisons. Participants received results by text (HIV antibody/ HCV RNA not detected) or a healthcare provider (HIV antibody/ HCV RNA detected). The RE-AIM framework was used to evaluate reach, effectiveness, adoption, and implementation.

RESULTS

Reach: Between November 2016 and December 2020, 7,392 individuals were tested for HIV and/or HCV (21% self-registration, 34% assisted in community, and 45% assisted in prison).

EFFECTIVENESS

Of 6,922 people tested for HIV (19% men who have sex with men, 13% living outside major cities, 21% born outside Australia), 51% (3,521/6,922) had no HIV test in the past two years, 0.1% (10/6,922) were newly diagnosed with HIV, and 80% (8/10) initiated HIV treatment within six months. Of 5,960 people tested for HCV (24% women, 35% Aboriginal and/or Torres Strait Islander, 55% recently injected drugs), 15% had detectable HCV RNA (878/5,960), and 45% (393/878) initiated treatment within six months. Adoption: By the end of 2020, DBS via assisted registration was available at 36 community sites and 21 prisons.

IMPLEMENTATION

90% of DBS cards arriving at the laboratory had the three full spots required for testing; the proportion was higher in assisted (94%) compared to online (76%) registration.

CONCLUSIONS

This study demonstrated the feasibility of DBS testing for HIV and HCV in key populations including Aboriginal and Torres Strait Islander peoples, men who have sex with men, people who inject drugs, and demonstrated the utility of DBS in the prison setting.

Hepatitis C Treatment Uptake Following Dried Blood Spot Testing for Hepatitis C RNA in New South Wales, Australia: The NSW DBS Pilot Study

Background

Dried blood spot (DBS) testing for hepatitis C virus (HCV) RNA provides a sampling option that avoids venepuncture and can be carried out in a nonclinical setting. Large-scale evaluations are needed to understand how DBS testing can reduce HCV burden. This study estimated prevalence of, and factors associated with, HCV RNA and treatment initiation among people enrolled in a state-wide pilot of people testing in the NSW DBS Pilot in New South Wales, Australia.

Methods

People at risk of HIV/HCV could participate via (1) self-registration online with a DBS collection kit delivered and returned by conventional postal service; or (2) assisted DBS sample collection at a community site or prison. Logistic regression was used to identify factors associated with detectable HCV RNA and treatment initiation within 6 months of testing.

Results

Between September 2017 and December 2020, 5960 people were tested for HCV (76% men, 35% Aboriginal and/or Torres Strait Islander, 55% recently injected drugs): 21% online self-registration, 34% assisted registration in the community, 45% assisted registration in prison. Fifteen percent had detectable HCV RNA (878/5960). Overall, 44% (n = 386/878) of people with current HCV initiated treatment within 6 months (13% online self-registration, 27% assisted registration in the community, 61% assisted registration in prison). Testing in prison compared with the community (adjusted odds ratio [aOR], 4.28; 95% CI, 3.04-6.03) was associated with increased odds of treatment initiation. Being a woman compared with a man (aOR, 0.68; 95% CI, 0.47-0.97) was associated with reduced treatment initiation.

Conclusions

The NSW DBS Pilot demonstrates the feasibility of using DBS to promote HCV testing and treatment in community and prison settings.

Dried blood spot eluates are suitable for testing of SARS-CoV-2 IgG antibodies targeting Spike protein 1 and Nucleocapsid protein

Dried blood spots (DBS) provide easy handling and are thus a beneficial tool for data collection, e.g. for epidemiological studies. The suitability of DBS for the assessment of antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was analyzed with regards to the use in future studies addressing seroprevalence in the population. 121 volunteers gave a venous blood sample and capillary blood samples on two DBS cards (PerkinElmer and Ahlstrom-Munksjö) via self-sampling under supervision. All samples were analyzed using the Anti-SARS-CoV-2 ELISA (IgG) and the Anti-SARS-CoV-2 NCP ELISA (IgG) from EUROIMMUN performed on the EUROIMMUN EUROLabWorkstation ELISA. Correlation coefficients between ELISA results based on the different sampling methods were calculated. Results of DBS analysis for SARS-CoV-2 IgG S1 and NCP highly correlated with the serum values (r = 0.96). In addition, the calculation of the phi coefficient showed no significant difference between the qualitative results of both sampling methods (r_φ = 0.98-1.0). Further analysis of DBS eluates after prolonged storage of 6-8 h also showed a high correlation with serum results (r = 0.97 and r = 0.93, respectively). The study results indicate suitability of DBS for the analysis of antibodies against SARS-CoV-2 S1 and NCP. For DBS eluate, a stability of 6-8 h for measurement of SARS-CoV-2 antibodies can be assumed.