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An Assessment of a Novel Capillary Blood Collection System for Research Sample Collection in Adults

Laboratory Genetics and Genomics
  • Primary Categories:
    • Population Genetics
  • Secondary Categories:
    • Population Genetics
Introduction:

Research sample collection faces barriers such as collection site accessibility, scheduling time, patient discomfort, and staff resources. Venipuncture is a common sample collection method for genetic research. However, it requires trained staff to perform the procedure and for participants to visit a phlebotomy site. While at-home saliva kit collection has helped increase accessibility for genetic testing, they yield inconsistent results due to contamination and insufficient DNA quality and quantity. Previous research from our group has shown that capillary blood collection in infants can provide consistent high-quality DNA for genomic analysis (ACMG 2023, PB3146). However, this has not yet been tested in an adult cohort. Here, we compare the yield from capillary blood collection and saliva kits in this cohort of participants from the Electronic Medical Records and Genomics study (eMERGE) cohort.




Methods:
This study utilized the Neoteryx Mitra® volumetric absorptive microsamplers (VAMs). Patients were eligible to enroll in the eMERGE study and receive a genetic report if they were between ages 3-75 and if they had a PCP within the Massachusetts General Brigham system (MGB) and provided a DNA sample. Polygenic risk score testing required a minimum of 40uL in sample volume with a concentration of ~60ng/uL and a suggested ~2-2.5ug gDNA for genotyping at the Broad Institute. Capillary sampling was offered to patients if 2 previous samples (venipuncture or saliva) failed DNA extraction or if their sample was collected in the last 4 months of recruitment. Patients were mailed 30 microliter Mitra clamshell (4-samplers) kits and instructed to fill the blood collection device tips until saturated. Participants were then instructed to mail kits to the Laboratory for Molecular Medicine (LMM) at Mass General Brigham for DNA extraction within 24 hours. Extraction using membrane spin columns (QIAamp DNA Investigator Kit, QIAGEN) was utilized for sample preparation.

Results:
A total of 2747 samples from 2565 patients were collected throughout the eMERGE study. Venipuncture was primarily used in this study accounting for 60.2% (n=1654) of the samples, followed by saliva (n= 1057; 38.5%) and capillary blood (n= 36; 1.3%). Capillary testing had a lower rate of failure during DNA extraction at 13.9% (n=5) with saliva at 19.6% (n= 207). Average yield of capillary sampling was 1.66ug. When used in infants from the BabySeq study, this technique yielded an average of 2.39 ug for the 119 samples tested (unpublished data). Saliva samples had a lower Broad assay failure rate of 2.3% (n=20) than capillary testing at 6.4% (n=2). The 7 capillary testing failures were due to failure to saturate the collection tips (n=3; 42.9%) and DNA extraction (n=2; 28.5%) and assay failure (n=2; 28.5%).

Conclusion:
This study found that capillary collection methods had a lower extraction failure rate than saliva and may provide a reliable and accessible option for research participants. We believe the assay rate of failure was higher for capillary samples due to sending less than the requested gDNA amount. While not optimal for this study, the extracted capillary gDNA may have been a sufficient yield for other studies such as BabySeq (required .75ug) and wouldn’t have been an overt failure. Possible reasons for capillary sample failure included <50% saturation of the collection swab and potential patient discomfort. Additional patient education around how to effectively use these kits may decrease failure rates in the future. While saliva and capillary had similar rates of failure, this dataset does not capture the saliva failures due to incomplete sealing of sample tubes or sample loss during transport. Given this, capillary sampling is an effective and accessible alternative for adult participants who cannot access venipuncture or saliva sampling and should be considered in research studies.

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