Abstract
BackgroundThe prevalence of allergic and autoimmune conditions has been steadily increasing in wealthy nations over the past century. One hypothesis put forward to explain this is the Old Friends Hypothesis, which posits that increased hygiene, urbanization, and lifestyle changes have reduced our exposure to parasites and microbes that we co-evolved with, resulting in immune dysregulation. However, research in traditionally living populations, who are exposed to greater parasite and pathogen loads such as those encountered during our evolution, is limited, in part due to a lack of minimally invasive, field-friendly biomarkers of autoimmune disorders. We therefore developed an ELISA to assess positivity for thyroid peroxidase autoantibody (TPO-Ab), an indicator of autoimmune thyroid disease, based on dried blood spot (DBS) samples.ResultsWe used the Accubind anti-thyroid peroxidase test system to screen our validation samples comprising matched fingerprick DBS, venous DBS, and plasma samples from 182 adults. After confirming that we had TPO-Ab-positive individuals in our validation sample (n = 12), we developed an indirect ELISA to measure TPO-Ab levels from one 3-mm DBS punch. The sensitivity and specificity of our assay for DBS samples ranged from 91.7–100% and 98.2–98.8%, respectively, using a cut-off value of ≥ 26 IU/mL. Intra-assay reliability for duplicate quality control DBS punches was 5.2%, while inter-assay reliability ranged from 11.5–24.4% for high, medium, and low DBS controls. Dilutional linearity ranged from 80 to 120%, and spike and recovery experiments indicated that the DBS matrix does not interfere with the detection of TPO-Ab. TPO-Ab levels remained stable in DBS samples stored at − 28 °C or − 80 °C, but decreased over time in DBS samples kept at 22 °C or at 37 °C.ConclusionsWe developed an in-house, kit-independent indirect ELISA assay to determine individuals’ TPO-Ab positivity based on dried blood spots, representing a cost-effective method with potential applications in a range of research settings.
Highlights
The prevalence of allergic and autoimmune conditions has been steadily increasing in wealthy nations over the past century
While indirect testing of the Old Friends Hypothesis has been conducted in traditionally living populations by assessment of biomarkers of inflammation in dried blood spot (DBS) samples, direct testing with autoimmune and parasitic burden data has been mostly limited to studies conducted in wealthy nations [3]
Combined with altered lifestyles related to the Old Friends Hypothesis, the ability to monitor Autoimmune thyroid disorder (AITD) prevalence in these populations is crucial for understanding biocultural relationships and adaptive tradeoffs related to indigenous health
Summary
The prevalence of allergic and autoimmune conditions has been steadily increasing in wealthy nations over the past century. While indirect testing of the Old Friends Hypothesis has been conducted in traditionally living populations by assessment of biomarkers of inflammation in dried blood spot (DBS) samples, direct testing with autoimmune and parasitic burden data has been mostly limited to studies conducted in wealthy nations [3]. Biological anthropologists are ideally positioned to test the Old Friends Hypothesis because of their frequent work with both traditionally living populations and populations in early stages of market integration, the lack of minimally invasive, field-friendly biomarkers of autoimmune disorders has limited relevant research. Cold-adapted populations upregulate basal metabolic rates for increased internal heat production via elevations in thyroid hormone production [5,6,7] This upregulation may work to prematurely exhaust the thyroid gland, resulting in higher rates of AITDs among these populations [8]. Combined with altered lifestyles related to the Old Friends Hypothesis, the ability to monitor AITD prevalence in these populations is crucial for understanding biocultural relationships and adaptive tradeoffs related to indigenous health
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