Deep in a refrigerated repository in Sweden lies one of the most remarkable biomedical archives in the world: the Phenylketonuria screening biobank, a collection of neonatal dried blood spots from every child born in Sweden since 1975. With roughly 115,000 newborns added each year, the biobank now holds samples from more than five million individuals, each Guthrie card accompanied by detailed metadata covering maternal information, birth details, and the precise timing of collection. For decades, this resource has fueled genetic, metabolic, and molecular research, but one frontier remained uncertain: whether these decades-old spots, stored on filter paper at 4 degrees Celsius and 30 percent humidity, could yield reliable DNA methylation profiles using the most advanced modern arrays. A new pilot study now answers that question with a resounding yes, opening the door to epigenetic studies on a population scale.
The study, published in Epigenetics Communications by researchers at Karolinska Institutet and their collaborators in Denmark and the United States, set out to test whether the Illumina Infinium MethylationEPIC v2.0 array could produce high-quality data from archival newborn blood spots using vanishingly small amounts of DNA. This is no trivial challenge. The EPIC v2.0 array, which profiles approximately 937,000 cytosine-phosphate-guanine sites across the genome, officially recommends between 250 and 500 nanograms of DNA as input material. Decades-old dried blood spots, however, typically surrender far less genetic material, often well below 100 nanograms per sample, raising serious doubts about whether the resulting methylation data would be complete, accurate, and free of technical artifacts.
To find out, the team selected seven random samples from individuals born between 1985 and 2003, meaning the blood spots had been stored for periods ranging from 18 to 40 years. The laboratory workflow began with two 3-millimeter punches from each blood spot, which were placed into 96-well plates. Proteins and metabolites were eluted by incubating the punches in phosphate-buffered saline for two hours at room temperature on a rotary shaker, after which DNA was extracted using the Highprep Blood and Tissue DNA kit from MagBio Genomics, processed on an automated Beckman Coulter BioMek I7 liquid handler and eluted in a final volume of 50 microliters. After a portion of the extract was used for genotyping on an Illumina Global Screening Array, the remainder was carried forward to bisulfite conversion and methylation profiling at the National Genomic Infrastructure in Uppsala, part of Science for Life Laboratory.
The DNA volumes recovered from these archival spots ranged from just 19.2 nanograms to 99.2 nanograms, figures dramatically below the manufacturer’s recommended input of 250 nanograms, with the lowest sample representing less than 10 percent of the prescribed amount. Yet when the raw data came back from the array, the results were extraordinary. Probe call rates, the proportion of methylation sites successfully measured in each sample, averaged 99.75 percent at the conventional significance threshold of p less than 0.01, comfortably exceeding the greater than 98 percent benchmark commonly used to define successful probe detection in methylation studies. Coverage remained robust across all seven samples, with between 930,588 and 936,110 probes reliably detected, close to the array’s full complement of sites.
Quality control went well beyond call rates. The researchers examined the balance between methylated and unmethylated signal intensities, a key indicator of whether DNA degradation or processing problems have distorted the underlying signal. All seven samples clustered tightly around expected values, with median methylated intensity spanning a log-two range of 11.34 to 12.07 and median unmethylated intensity between 10.36 and 10.82, and no outliers emerged from the group. The team also calculated pairwise sample-to-sample Pearson correlations across the full set of genome-wide beta values, which ranged from 0.972 to 1.000. Such uniformly high correlations indicate consistent methylation profiles, reproducible processing, and, crucially, the absence of batch effects, a common scourge of microarray experiments that can masquerade as biological signal.
The fundamental structure of the methylation data also held up under scrutiny. Raw beta value distributions displayed the characteristic bimodal pattern expected of high-quality methylation data, with the vast majority of CpG sites falling into clearly methylated or clearly unmethylated classes and relatively few occupying intermediate values. This bimodality was preserved after noob normalization, a preprocessing step implemented in the R Bioconductor package minfi that corrects for background signal and dye bias, and the normalized density curves showed slightly improved alignment across samples. Embedded control probes monitoring bisulfite conversion, staining, hybridization, target removal, extension, and specificity all performed within expected ranges, with negative control signals remaining low and target-removal controls showing appropriately reduced signal compared with hybridization controls, together indicating minimal background fluorescence and efficient chemistry at every step.
The significance of these findings extends far beyond a single national biobank. DNA methylation, the chemical modification of DNA that influences gene activity without altering the underlying sequence, is increasingly recognized as a record of early-life biology and environmental exposure. Because newborn blood spots capture the epigenome at the very beginning of life, the ability to profile them retrospectively gives researchers a unique window into the molecular conditions present at birth, potentially decades before the onset of disease. Previous work had already shown promise: two earlier studies using the older Infinium 450K array achieved correlations exceeding 0.99 between dried blood spot samples and matched frozen blood fractions, and one proof-of-principle study using the HumanMethylation27 BeadChip demonstrated that neonatal blood spots stored for 26 and 28 years produced methylation profiles nearly identical to adult reference samples with only 30 nanograms of DNA. Other evaluations had pushed the EPIC v2.0 array to inputs as low as 1 nanogram, but only with fresh cell line DNA, never with archival clinical material stored at refrigeration temperatures.
What distinguishes the new study is precisely this combination of archival age, real-world storage conditions, and ultra-low input on the current-generation platform. The samples in the analysis had endured 18 to 40 years of refrigerated storage with variable collection dates, and none showed evidence of degradation-related signal imbalance. The authors note that while Kaur and colleagues had previously demonstrated adequate EPIC v2.0 performance with 1-nanogram inputs using fresh DNA, the present results extend those findings to the far more demanding context of decades-old clinical biobank samples, where DNA may be fragmented, chemically modified, or partially degraded by years of storage.
The limitations of the pilot are nonetheless clear and acknowledged by the team. Seven samples cannot establish population-level generalizability, and future work will need to validate these results in larger cohorts with broader demographic representation. Moreover, all samples analyzed had been collected after 1981 and therefore stored under controlled refrigerated conditions. Samples from before 1981, which spent their early years at room temperature, may behave differently and will require separate validation, although encouraging results from dried blood spots stored three to ten years at room temperature using the older 450K platform have been reported by Joo and colleagues and by Walker and colleagues, suggesting that even less favorable storage histories may not be disqualifying.
Even so, the proof of principle is transformative. The Swedish PKU biobank, with its five million-plus samples collected systematically since 1975 under Swedish Biobank Law provisions that permit ethically approved research use, now stands as an invaluable resource for large-scale epigenetic investigation into conditions ranging from neurodevelopmental disorders to cardiovascular and metabolic disease. Neonatal screening biobanks of similar design exist around the world, collectively representing millions of additional archived samples that could become accessible to methylation profiling. The study was approved by the Swedish Ethical Review Authority without individual informed consent, with all data handled in deidentified form in accordance with GDPR and Swedish legislation. For researchers who have long dreamed of tracing the epigenetic origins of disease back to the first days of life, the message of this small but rigorous study is unmistakable: the molecular memory written into a newborn’s blood can survive decades in a cold archive, and modern technology can now read it with remarkable fidelity, even from less than one-tenth of the DNA the platform’s designers thought necessary.
Subject of Research: DNA methylation profiling of archival neonatal dried blood spots using the Illumina MethylationEPIC v2.0 array with ultra-low DNA input
Article Title: Performance of the Illumina Infinium MethylationEPIC v2.0 array with low DNA input from Swedish neonatal dried blood spots
Article References: Brander, G., Karlsson, H., Dalman, C., Bybjerg-Grauholm, J., Crowley, J. J., & Mataix-Cols, D. (2025). Performance of the Illumina Infinium MethylationEPIC v2.0 array with low DNA input from Swedish neonatal dried blood spots. Epigenetics Communications, 5(1), Article 9. https://doi.org/10.1186/s43682-025-00042-2
Image Credits: AI Generated
DOI: 10.1186/s43682-025-00042-2
Keywords: DNA methylation, dried blood spots, MethylationEPIC v2.0, neonatal biobanks, epigenetics, low-input DNA, archival samples, PKU biobank, quality control, Illumina, Swedish biobank, CpG sites
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Harold Sullivan. (September 22, 2026). Decades-Old Newborn Blood Spots Yield High-Quality DNA Methylation Data With Tiny DNA Inputs. Scienmag. https://scienmag.com/decades-old-newborn-blood-spots-yield-high-quality-dna-methylation-data-with-tiny-dna-inputs/
Harold Sullivan. “Decades-Old Newborn Blood Spots Yield High-Quality DNA Methylation Data With Tiny DNA Inputs.” Scienmag, 22 September 2026, https://scienmag.com/decades-old-newborn-blood-spots-yield-high-quality-dna-methylation-data-with-tiny-dna-inputs/. Accessed 22 September 2026.
Harold Sullivan. “Decades-Old Newborn Blood Spots Yield High-Quality DNA Methylation Data With Tiny DNA Inputs.” Scienmag. September 22, 2026. https://scienmag.com/decades-old-newborn-blood-spots-yield-high-quality-dna-methylation-data-with-tiny-dna-inputs/
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Tags: archival blood sample analysisarchival samplesCpG sitesDNA MethylationDNA methylation profilingdried blood spotsepigenetic research on stored samplesepigeneticshigh-throughput methylation data from minimal DNAhistorical blood spot biorepositoriesIlluminaIllumina MethylationEPIC array validationlarge-scale epidemiological epigeneticslong-term sample preservation effects on DNA qualitylow-input DNAMethylationEPIC v2.0neonatal biobanksneonatal biobanks for DNA methylationneonatal dried blood spotsPKU biobankpopulation-scale epigenetic studiesquality controlSwedish biobankvalidation of epigenetic methods on aged samples
