Analysis of Inflammatory Biomarker Changes in Dry Blood Spot Versus Venous Blood Samples

Inflammation plays a key role in the progression of both acute and chronic health conditions. When properly regulated, inflammatory responses enable the body to adapt to short-term stressors such as infection, vaccination, or strenuous exercise.1 In contrast, excessive and/or prolonged inflammation can lead to the development and progression of chronic health conditions including cardiovascular disease, autoimmune disorders, and metabolic dysfunction.2 In both acute and chronic settings, measuring changes in inflammatory biomarkers allows us to better understand how the immune system responds to physiological challenges, which may ultimately support the development of earlier testing (diagnostic) strategies, more accurate detection methods, and timely interventions for individuals most at risk.

Venous blood sampling is the gold standard for measuring inflammatory biomarker concentrations. However, venous blood sampling is invasive, requires trained personnel, and entails a visit to a hospital or health clinic.3 Dependence on venous sampling for inflammatory biomarker detection therefore limits the feasibility of decentralized, real-world investigations, such as those conducted in home environments. This restriction reduces opportunities for longitudinal data collection and poses challenges for larger-scale and/or high temporal frequency sampling protocols.

More recently, dried blood spot (DBS) samples have shown to be a compelling alternative to assess inflammatory biomarkers like C-reactive protein (CRP) in the blood. In comparison, this method is minimally invasive, can be obtained by the patient rather than trained personnel, involves fewer requirements for transport and storage, and is less costly than venous blood sampling.3-7 Previous comparative studies between venous blood sampling and DBS, have shown the latter's potential for measuring a wide range of indices, including inflammatory biomarkers during both chronic and acute medical conditions. In fact, numerous studies have shown good concordance between the DBS and venous blood sampling methods, namely for CRP, interleukin (IL)-6, IL-10, and tumor necrosis factor alpha (TNF-α).3,8-13 Furthermore, a recent study by Anderson et al. demonstrated that DBS can reliably capture dynamic changes in 12 inflammatory biomarkers (incl., serum amyloid A (SAA), myeloperoxidase (MPO), immunoglobin M (IgM)) across diverse conditions (infection, vaccination, surgery, exercise, Crohn's disease) and over both acute and chronic timescales; however, these markers have yet to be directly compared to venous blood sample analysis.14 It is not yet well enough established whether inflammatory biomarkers can be measured from DBS with the same quality, sensitivity, and reproducibility as from venous blood samples, while certain gaps remain regarding how DBS performs when capturing acute, stressor-induced fluctuations in circulation concentrations of inflammatory biomarkers. Addressing these gaps is critical to determine whether DBS can serve as a valid substitute for venous blood sampling in research and clinical contexts. Based on these considerations, this study aims to validate the measurement of change in inflammatory biomarkers obtained in DBS compared with paired venous blood samples following a controlled physiological stressor, using a comprehensive (48-plex) inflammatory biomarker panel.

The overarching aim of this study is to validate and compare the measurement of changes in inflammatory biomarkers obtained from dried blood spot (DBS) samples against paired venous blood samples, using the Human Cytokine/Chemokine Panel A 48-Plex (HD48A).

• Venous blood sampling (Diagnostic test): -Venous blood samples (1-2 mL) will be collected into EDTA and serum-separator vacutainer tubes. Samples will be processed within one hour by centrifugation (1,500g, 10 min, 4°C), and plasma/serum aliquots will be stored at -80°C
• Dried blood spot sampling (Diagnostic test): -DBS samples will be collected via finger prick (using a lancet) onto certified filter paper (Dried Blood Spot Sample Collection Kit with Lancets, Salimetrics, LLC; State College, PA, USA). Two blood spots (\~20 µL each) will be dried at room temperature for at least two hours, then stored in a sealed bag at -20°C with desiccant. Validated guidelines for the collection, storage and preparation of DBS samples will be followed to ensure proper quality control.

Primary outcomes

• Concordance between inflammatory biomarker concentrations measured in DBS samples and paired venous blood samples [Enrollment to 3 days after exposure of stressor]: Agreement and variability between both sample types will be measured using multiple approaches: * coefficients of variation * intraclass correlation coefficients (ICC) * Pearson correlation coefficients * Bland-Altman analyses.

Sex: All, ages: 18 Years to any

Inclusion Criteria:

* Men or women aged ≥18 years, who are planning to receive a seasonal vaccine OR have a scheduled acute stressor*.

Exclusion Criteria:

* Any infectious symptoms (fever, cough, rhinorrhea, sore throat, diarrhea, loss of smell or taste) within the previous 7 days
* Any self-reported active/recent use of cocaine, injection drugs, or amphetamines
* Acute worsening of a known chronic health condition within the previous 30 days (e.g., of IBD, COPD, asthma, rheumatologic disease)
* Known severe allergy or intolerance to the planned vaccine
* Contraindication to the vaccine received, if applicable

  *List of possible scheduled acute stressors include:
* Hard exercise (incl. 10km run or longer, high-intensity interval training, or comparable endurance activity)
* Social event with moderate alcohol consumption
* Planned change in medication dose and/or frequency of use
* Onset of menstruation (day 1)
* Other pre-planned stressors expected to elicit an inflammatory response

• Emily G. McDonald, MD MSc, Principal investigator, McGill University Health Centre/Research Institute of the McGill University Health Centre