5 Ways in Which Fingerstick Blood Testing Is Transforming Healthcare

Fingerstick testing is a patient-friendly microsampling method that involves the use of a lancet to draw a few drops of capillary blood from a fingertip. The procedure is minimally invasive compared to a standard (venous) blood draw. A similar method is used in newborn screening, which is typically carried out during the first hours or days of a newborn’s life. Here, a few drops of blood are collected from the heel – the so-called heel-prick test.

Fingerstick blood is ideal for a range of diagnostic applications, such as self-sampling at home and in remote locations, rapid diagnostic tests and point-of-care devices. The approach offers many advantages over venous blood draws, both for the individual being tested and healthcare services:

• The minimally-invasive procedure increases patient comfort, especially for children and individuals who require regular testing to monitor disease progression or response to treatment.
• The use of a specialised blood collection device that can collect and store the blood as a dried blood spot (DBS) allows for home sampling, further increasing patient comfort, and allowing shipment of dried samples at ambient temperature.
• The possibility of self- and home-sampling reduces the need for trained phlebotomists in healthcare facilities and allows for sampling in remote areas.
• For individuals requiring regular testing, the ease of being able to sample at home may increase patient compliance, leading to better health/treatment outcomes and reducing the burden on healthcare services.

Let’s take a closer look at 5 areas where fingerstick testing is already transforming healthcare!

1. Fingerstick blood testing for metabolic disease monitoring

Since the 1960s, the use of microsampling via DBS technology for newborn screening and monitoring of patients with inherited metabolic disorders has become routine in most parts of the world. Here, a heel-prick blood sample (from babies) or fingerstick blood sample is collected and put through various tests to detect certain proteins, minerals, and other analytes known to be implicated in genetic disorders.

Within metabolic disease monitoring, the rare but potentially fatal autosomal recessive condition phenylketonuria (PKU) provides an excellent example of a disease that when detected early, can be managed by dietary changes that greatly improve outcomes for those affected by it. For this reason, screening and monitoring of PKU in the first few days after birth has become standard practice in virtually all countries in which PKU is prevalent.

Continuous advances in quantitative DBS microsampling coupled with improvements in biomarker detection methods provide vast opportunities for rapid and high-throughput screening and monitoring of many analytes in the future, where non-invasive microsampling, sample transportation, accurate detection, and cost-effectiveness stand to greatly improve the lives of individuals living with inherited metabolic diseases and other genetic disorders.

2. Therapeutic drug monitoring – guiding clinicians to find the right dose for optimal treatment

Therapeutic drug monitoring (TDM) involves measuring the concentration of specific drugs in an individual’s bloodstream at set time intervals. The overall goal of TDM is to maintain a constant blood concentration at which a given drug is safe and effective. TDM is not performed for all drugs, but where relevant, it can help doctors to find the ‘right’ dose for drugs that might be challenging to dose. The approach is also useful for monitoring drugs with narrow therapeutic ranges, as well as drugs that cause harmful side effects, and drugs for which target concentrations are difficult to monitor.

Today, the TDM procedure usually starts with collecting venous blood samples from patients in special medical facilities, and these samples are put through a range of laboratory tests. TDM is a complex multidisciplinary discipline that requires many factors to be considered when determining blood drug concentrations and suitable dosages. Since many of the drugs monitored this way are administered to patients long-term or even life-long, TDM usually requires regular and repeated testing in the same individual over long time periods. For individuals affected by complex medical conditions who may also be immunosuppressed, regular visits to medical facilities for TDM testing may not always be feasible.

With its many advantages including ease of use, fingerstick testing has the potential to transform the TDM experience for patients, while also reducing the resource demands on healthcare facilities, e.g., by eliminating the need for regular phlebotomy. Although not yet part of the routine workflow, microsampling has been explored with promising results in TDM applications for several drug types, including antimicrobials, anti-seizure drugs, antidepressants, anti-cancer drugs and immunosuppressive drugs (reviewed in 1).

In January 2023, researchers in Sweden reported that volumetric dried blood spot testing holds promise for lithium monitoring during the treatment of bipolar disorder. Their findings, published in Journal of Pharmaceutical and Biomedical Analysis, demonstrate a strong linear correlation between lithium concentrations in dried blood spot fingerstick samples collected using Capitainer®B,which is based on fingerstick collection of dried blood spots, and venous blood samples (2). This is a significant advance given the very narrow therapeutic range of lithium, which means that there is only a small difference between the minimum effective concentration and the minimum toxic concentration in the blood.

At present, individuals receiving lithium treatment for bipolar or other psychiatric disorders are typically monitored by venous blood draw at least every three to six months. Such frequent testing is not only resource-intensive but also leads to risk of non-compliance/failure to show up for testing, which can make lithium treatment unsafe in certain situations. The study from Sweden highlights for the first time the potential of using volumetric microsampling to develop a patient-centric approach to lithium monitoring, and raise hopes for safer and more accessible treatment with one of the most effective drugs in psychiatry.

3. Accurate blood alcohol and anti-doping testing

PEth blood alcohol testing is used to identify long-term alcohol consumption by measuring the blood levels of phosphatidylethanol (PEth). PEth is a phospholipid that exists naturally in red blood cells, and its formation in the blood is catalysed by the enzyme phospholipase D (PLD) in the presence of ethanol. This means that the levels of PEth in the blood increase with frequent alcohol consumption, making PEth a useful biomarker. A major advantage of fingerstick testing here is that it eliminates the need for a phlebotomist, making it possible to perform testing at workplaces and sites without access to trained healthcare personnel. Additionally, fingerstick testing is much less invasive than a standard blood draw, thus improving patient comfort.

Fingerstick PEth testing via dried blood spots has gained interest in recent years, but with the drawback of high-volume CV% of standard DBS caused by the haematocrit effect and sample quality factors. Recent technological advances made by Capitainer have led to a highly accurate PEth sampling device that provides volume control and eliminates the risk of falsely elevated PEth levels due to post-sampling formation. This advance builds upon knowledge that in vitro PEth formation can be prevented by inhibiting PLD activity immediately after blood sampling.

Anti-doping testing, which is performed in the sporting world to check for the use of performance-enhancing drugs, is also resource-intensive, and the need for regular venous blood draws may be uncomfortable for those being tested. Indeed, The World Anti-Doping Agency (WADA) has been working towards implementing a DBS sampling method for anti-doping testing since 2019, in collaboration with the International Olympic Committee and several international and national testing agencies. WADA requires a minimum of approximately 20-40 µL of capillary blood for routine monitoring of doping substance usage (3), a volume which is possible to collect using Capitainer’s larger-volume fingerstick collection device Capitainer®B 50.

Capitainer®B 50 collects 2×50 µL of blood and allows the patient to fill the metering channels by multiple drops until the required volume is met.

4. Serology and pandemic response

Fingerstick testing gained much attention during the COVID-19 pandemic, as it represents a relatively easy way to collect blood from large populations of people, including those in remote areas. Sero-epidemiology, which involves analysing the presence and titres of certain antibodies in the blood is a crucial part of the response to any pandemic or local disease outbreak. It helps to shed light on the long-term immune response to infection and vaccination, to evaluate the impact of transmission control strategies and vaccination programmes, and to assess previous infection history within populations when a new virus or variants of an existing virus emerge.

In 2021, Capitainer’s microsampling device Capitainer®B was selected by the Swedish Public Health Agency as a home-sampling device for a national point seroprevalence study to determine country-wide exposure to or vaccination against SARS-CoV-2 in Sweden during 2021 and 2022. Using that device, the study yielded a successful sampling rate >95 % and revealed laboratory analysis with DBS fingerstick samples to be as accurate as conventional serum analysis (4).

This development really illustrates the potential of fingerstick testing to increase access not only to COVID-19 tests, but also to diagnostics more broadly in large geographic areas, including sparsely population regions that are over-represented by elderly people living alone. Indeed, a retrospective cohort study published earlier this year found that home sampling with Capitainer®B did increase accessibility to COVID-19 antibody testing in the Sweden’s large but sparsely populated Västerbotten Region, compared to regular blood sampling at health clinics (5). This study is the first to demonstrate the impact of increased access to diagnostics with home sampling versus traditional venous blood sampling in a western country.

Within serology, fingerstick blood can be used for individual rapid antibody/antigen blood tests, as well as broader sero-epidemiological studies to monitor biomarkers of past infection or immunisation, acquired naturally or through vaccination.

5. Fingerstick blood testing in primary healthcare

As microsampling technology and detection methods advance further, we are likely to see more fingerstick testing when we visit the GP, as well as widespread use of the method in the management of chronic diseases. For instance, fingerstick testing is already widely used for self-monitoring of blood glucose levels (to manage diabetes), to measure CRP (C-reactive protein) in primary healthcare to direct decision making for infectious disease treatment, and to measure haemoglobin using point-of-care devices to monitor for anaemia.

Other major applications where fingerstick microsampling could transform patient comfort include paediatric care, e.g., to rapidly diagnose infections, anaemia, or other nutritional deficiencies in a minimally-invasive manner, prenatal care, e.g., monitoring for early detection of pre-eclampsia, anaemia, infection and gestational diabetes, and geriatric care, where one can be monitored for a range of health conditions from the comfort of their own home.

In summary, fingerstick testing has already made huge contributions to healthcare with widespread use in newborn screening and metabolic disease monitoring. The method has massive potential to transform future responses to pandemics and local disease outbreaks. Although not discussed in detail here, fingerstick testing has also shown promise in biomarker detection, with recent proof-of-concept for the detection of biomarkers for atherosclerotic cardiovascular disease.

Finally, and perhaps most importantly, fingerstick testing improves the overall patient experience by reducing discomfort and removing the need for regular travel to healthcare facilities. In a modern world where people want to be in control of their own health, fingerstick testing could be the perfect bridge between the patient, who can test themselves at home, and the healthcare provider, who can relay test results and provide advice over the phone or via other modern telecommunications methods.

References

1. Wilhelm, A. J., den Burger, J. C., Swart, E. L. (2014). Therapeutic drug monitoring by dried blood spot: progress to date and future directions. Clin Pharmacokinet,53:961–973. doi: 10.1007/s40262-014-0177-7.
2. Wikström F, Olsson C, Palm B, Roxhed N, Backlund L, Schalling M, Beck O. (2023). Determination of lithium concentration in capillary blood using volumetric dried blood spots. J Pharm Biomed Anal. 227(115269), doi: 10.1016/j.jpba.2023.115269.
3. World Anti-Doping Agency 2021 Code Implementation Support Program Guidelines for Sample Collection. Accessed 7th August 2023.
4. Beser J, Galanis I, Enkirch T, et al. Seroprevalence of SARS-CoV-2 in Sweden, April 26 to May 9, 2021. Sci Rep. 2022. 25;12(1):10816. doi: 10.1038/s41598-022-15183-w.
5. Byström JW, Vikström L, Rosendal E, et al. At-home sampling to meet geographical challenges for serological assessment of SARS-CoV-2 exposure in a rural region of northern Sweden, March to May 2021: a retrospective cohort study. Euro Surveill. 2023. 28(13):2200432. doi: 10.2807/1560-7917.ES.2023.28.13.2200432.