A team of Vancouver investigators, led by Dr. Agatha Jassem of the British Columbia Centre for Disease Control (BCCDC) and partially funded by the CITF, assessed SARS-CoV-2 serological testing using two methods: finger pricking (dried blood spot or DBS) and traditional venipuncture (blood draw with a needle). Their observations, in pre-print and therefore not yet peer reviewed, conclude that samples obtained with a finger prick are a valid alternative to traditional venipuncture to reliably detect SARS-CoV-2 antibodies.

Key Points:

  • Samples from two methods, finger prick capillary dried blood spot (DBS) and traditional venipuncture collection of blood from a vein, usually done by a trained personnel serum collection were obtained from 644 individuals in British Columbia, between January 2020 and May 2021.
  • Samples were tested for the presence of antibodies against several SARS-CoV-2 proteins (nucleocapsid, full spike protein, or spike protein’s Receptor Binding Domain) using Meso Scale Discovery assays.
  • Of the 644 samples tested: 593 were SARS-CoV-2 negative and 24 were SARS-CoV-2 positive using both methods. Six DBS samples tested false negative and twenty-one samples tested false positive in comparison  to the paired sera collected by  These results indicate that DBS has 80% sensitivity the ability of a test to correctly identify a positive result as positive and 96% specificity, the ability of a test to correctly identify a negative result as negative when compared to serum from venipuncture. Overall, a DBS collected sample will provide an accurate diagnosis 88% of the time.

These results are useful because DBS sampling by finger prick eliminates the need for trained medical personnel since samples are self-collected; this is therefore a more feasible method for community collection of blood samples. In addition, collection cards are stable at ambient temperature for up to two weeks, simplifying transport. The cards can also be stored in large quantities, requiring very little space during data collection. As observed with this study, tests performed on these types of samples characteristically exhibit high specificity and lower sensitivity, in part due to the low volume of sample collected (2-3 drops) and variations in collection practices. The comparable diagnostic accuracy closeness of the measurements to the real result, positive or negative to that of traditional venipuncture serum samples in addition to simpler collection requirements and an wider population out-reach, make serological testing from finger prick DBS a viable option in our strategies to understand and combat the spread of SARS-CoV-2.

 

Nikiforuk AM, McMillan B, Bartlett SR,  Márquez AC, Pidduck T,  Kustra J,  Goldfarb DM, Barakauskas V, Sinclair G,  Patrick DM,  Sadarangani M, Ogilvie GS, Morshed M, Sekirov, Jassem AN. Performance of Immunoglobulin G Serology on Finger Prick Capillary Dried Blood Spot Samples to Measure SARS-CoV-2 Seroconversion and Humoral Immunogenicity of COVID-19 Vaccination. medRxiv. July 31 2021. doi: https://doi.org/10.1101/2021.07.29.21261156