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Correspondence
Preservation of bacterial DNA in 10-year-old guaiac FOBT cards and FIT tubes
  1. Matheus Couto Furtado Albuquerque1,
  2. Yasmijn van Herwaarden2,
  3. Guus A M Kortman3,
  4. Bas E Dutilh4,5,
  5. Tanya Bisseling2,
  6. Annemarie Boleij1
  1. 1Deparment of Pathology, Radboudumc, Nijmegen, The Netherlands
  2. 2Department of Gastroenterology, Radboudumc, Nijmegen, The Netherlands
  3. 3Department of Laboratory Medicine, Radboudumc, Nijmegen, The Netherlands
  4. 4Department of Theoretical Biology and Bioinformatics, Utrecht University, Utrecht, The Netherlands
  5. 5Center for Molecular and Biomolecular Informatics (CMBI), Radboudumc, Nijmegen, The Netherlands
  1. Correspondence to Dr Annemarie Boleij, Department of Pathology, Radboudumc, Nijmegen, 6525 GA, The Netherlands; Annemarie.Boleij{at}radboudumc.nl, aboleij{at}gmail.com

https://doi.org/10.1136/jclinpath-2017-204592

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    With great interest we read the article of Taylor et al in the Journal of Clinical Pathology regarding the use of guaiac faecal occult blood test (gFOBT) cards for microbiome studies.1 gFOBT cards were found to be an easy to use option for stool collection and gained results comparable to fresh stool, even when cards were stored for up to 3 years at ambient temperature before DNA extraction. We would like to share our experience that even after 10 years of storage, gFOBT cards and faecal immunochemical test (FIT) tubes can be used to study the microbiome.

    Taylor et al conducted 16S rDNA amplicon sequencing for determination of outcome comparability within and between sample type and storage time.1 Between-subject differences greatly outweighed any differences by sample collection type (fresh vs gFOBT) and time spent at ambient temperature (from 2 weeks up to 3 years after development of the gFOBT cards), which was also reported previously.2–4 No appreciable differences within the three individuals with regard to microbial taxa composition, alpha and beta diversity index and intraclass correlation (ICC) were observed.1 In our analysis, we used gFOBT cards (Hemoccult II; Beckman Coulter) and FIT tubes (OC-sensor; Eiken Chemical) that were collected a decade ago to evaluate the positive predictive value and specificity of these tests in a colorectal cancer screening population.5 Storage times at ambient temperature ranged from 2 to 11 days before samples were developed and frozen at −80°C for long-term storage. From 5 FIT tubes and 12 gFOBT cards DNA was extracted with a protocol adjusted from the Human Microbiome Project including bead beating (see online supplementary file 1). DNA quantity and quality from these 10-year-old samples were evaluated and analysed with quantitative PCR (qPCR) for the most abundant phyla in stool.

    Supplementary file 1

    [SP1.docx]

    FIT tubes that were stored for 2–4 …

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