Dried Blood Spot Testing – Part 2

Welcome back to our series about dried blood spot (DBS) testing. In Part 1, we provided an overview of what DBS is, how it is performed, and we touched upon some of its many applications. In Part 2, we will dig into how DBS may be used in the diagnosis and monitoring of infectious diseases.

DBS – a quick recap

In brief, DBS testing is a microsampling method that is based on dried spots of whole blood. The method arose through the work of American microbiologist Robert Guthrie in the 1960s who sought to develop new ways to detect the rare metabolic disorder phenylketonuria (PKU). Since then, DBS has increasingly been used for the qualitative or semi-quantitative analysis of hundreds of molecules, including nucleic acids, small molecule therapeutics, proteins, and more (1).

DBS testing in infectious disease

The first references to the use of DBS for infectious disease diagnostics date back to the 1950s, where the method was used to detect syphilis (2). Later, throughout the 1970s and 1980s, DBS was employed in the diagnosis and serological monitoring of a number of infectious diseases, including trypanosomiasis, hepatic amoebiasis, congenital rubella, and hepatitis B. Increase in the use of DBS in diagnostics rose again around the turn of the millennium, primarily in response to the urgent need for therapeutic monitoring of HIV infection (see 3, and references therein).

Within infectious disease diagnostics and monitoring today, DBS samples can be used to measure antibody responses to pathogens, and to detect pathogen-derived antigens or pathogen-derived nucleic acids, using a range of standard laboratory analysis methods.

As well as providing a qualitative answer regarding the presence or absence of a pathogen, DBS testing can also be used to quantitatively monitor viral load or immunoglobulin titers in individuals already confirmed to have a chronic infection such as HIV, as well as monitoring the response to treatment by using viral/bacterial load or immunoglobulin titers as a readout.

Advantages of DBS testing in infectious disease diagnostics

In comparison to venous blood draws, DBS sampling devices make sample collection relatively easy and non-invasive. With the emergence of devices such as Capitainer®B, which is based on Capitainer’s proprietary qDBS technology, consistent and highly accurate DBS sampling is now possible. Because DBS samples can be stored and shipped as non-hazardous material at ambient temperatures, DBS has vast potential to improve diagnostics and care of infection in hard-to-reach populations or remote areas with high infection risk, in young and vulnerable individuals, as well as people living in low-income settings.

As well as the above benefits, DBS testing circumvents the need for a trained phlebotomist, making it an ideal and cost-effective choice for home/remote sampling for regular testing and monitoring of a diverse range of infectious diseases, including but not limited to, infectious diseases associated with poverty, pregnancy-associated infectious diseases and sexually-transmitted diseases.

By using a safety lancett, microsampling from the fingertip onto a DBS sampling card can easily be performed at home.

World Health Organisation recognises DBS testing for HIV, Hepatitis B and C

In 2020, the World Health Organisation (WHO) pre-qualified the Aptima HIV-1 Quant Dx assay (Hologic, U.S.) for testing of DBS samples. This in vitro PCR-based assay can be used with DBS samples to monitor viral load and disease progression among HIV-1-infected individuals, and to aid in the diagnosis of HIV-1 infected infants below the age of 18 months. The WHO pre-qualification programme is viewed as an international seal of approval attesting that products for certain diagnostics (as well as certain medicines and vaccines) meet acceptable standards for the way they are manufactured and how they work.

In addition, the WHO has also set out a manual of best practice recommendations for DBS samples in HIV-1 drug resistance genotyping as an alternative to the ‘gold standard’ plasma samples, since DBS sampling is more practical in rural, remote areas, as well as in lower income countries, where access to trained personnel and cold storage may not be feasible.

In its 2016 guidelines on hepatitis B (HBV) and C (HCV) testing, the WHO also states that capillary whole blood DBS sampling may be considered for antibody- and nucleic acid-based detection strategies for hepatitis B virus (HBV) and hepatitis C virus (HCV) infection to facilitate access to testing in situations where the facilities or personnel needed to take venous blood samples are lacking, as long as DBS sampling products and detection assays used are validated for this purpose.

Beyond the examples presented above, when available, DBS samples taken for newborn screening are further subjected to testing for cytomegalovirus (CMV) if an individual develops hearing problems, since congenital CMV (cCMV) infection is linked to hearing and other defects. Currently, retrospective cCMV diagnosis in children is only possible via testing the DBS samples collected shortly after birth (4). DBS samples are stored for different time spans depending on the NBS procedures in operation in different countries, but their potential for retrospective diagnosis for infectious and other diseases beyond those included in the NBS schedule may warrant longer term storage.

DBS in infectious disease research and serology

Beyond their use in infectious disease diagnostics, dried blood spots have been investigated as a sample matrix for the detection of diverse infections in research settings, e.g., antigen-specific antibody responses to cholera, enterotoxigenic E.scherichia. coli, and and typhoid fever, and PCR-based detection of Epstein Barr Virus, to name a few.

Given the advantages of DBS sampling over venous blood draws and its emergence in infectious disease diagnostics as presented above, it is not unlikely that DBS-based workflows for diagnosing and monitoring infectious diseases will gain traction in the future. Indeed, real-life experiences gained during the COVID-19 pandemic have demonstrated the power of DBS self-sampling in Sweden and in Canada, where DBS testing has been used to determine the spread of SARS-CoV-2 infection and the level of immunity within parts of the population. DBS has also been proven to work with modern multiplex serology applications such as the Luminex platform (5). These successes highlight the power of DBS and are likely to spur increased interest in self-sampling in the future.

Screening for infectious diseases during pregnancy – a role for DBS?

Screening for infectious diseases such as rubella, HIV, syphilis, toxoplasmosis and hepatitis B and C is a routine part of pre-natal care in much of the world. At present, these tests are primarily carried out on venous blood samples. Screening early in pregnancy allows for treatment to be initiated when necessary, to ensure the best possible outcome of the pregnancy.

Although not currently routine, pregnancy screening with DBS samples would offer significant advantages over venous blood draws, since home and remote sampling may be more comfortable for pregnant individuals who may or may not have mobility issues or underlying conditions that make healthcare visits challenging. DBS-based screening during pregnancy would also remove the geographical barriers that may exist in areas where healthcare is either too far away or difficult to access.

References

1. Moat, S. J., George, R. S., & Carling, R. S. (2020). Use of Dried Blood Spot Specimens to Monitor Patients with Inherited Metabolic Disorders. International Journal of Neonatal Screening, 6(26), doi: 10.3390/ijns6020026.
2. Blaurock, G., Rische, H., Rohne, K. (1950). Development of the blotting paper method in the dried blood reaction for syphilis. Dtsch Gesundheitsw 5(15), 462–464.
3. Tuaillon, E., Kania, D., Pisoni, A. et al. (2020). Dried Blood Spot Tests for the Diagnosis and Therapeutic Monitoring of HIV and Viral Hepatitis B and C. Front Microbiol, 11(373). doi: 10.3389/fmicb.2020.00373.
4. Pellegrinelli, L., Alberti, L., Pariani, E. et al. (2020). Diagnosing congenital Cytomegalovirus infection: don’t get rid of dried blood spots. BMC Infect Dis, 20: 217. doi: 10.1186/s12879-020-4941-z.
5. Roxhed, N., Bendes, A., Dale, M. et al. (2021). Multianalyte serology in home-sampled blood enables an unbiased assessment of the immune response against SARS-CoV-2. Nature Communications, 12(3695). doi: https://doi.org/10.1038/s41467-021-23893-4.