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Collection and analysis of DNA, most commonly from blood or buccal cells, is becoming more common in epidemiologic studies. Buccal samples, which are painless to take and relatively easily collected, are often the preferred source. There are several buccal cell collection methods: swabs, brushes, mouthwash, and treated cards, such as FTA or IsoCode cards. Few studies have systematically compared methods of buccal cell collection with respect to DNA yield and amplification success under similar conditions. We compared buccal DNA collection and amplification using buccal swabs and FTA cards in 122 control subjects from our Australian case-control study of childhood acute lymphoblastic leukaemia. Buccal DNA was quantified using a real-time PCR for beta-actin and genotyped at the loci of three polymorphisms (MTHFR 677C>T, ACE I/D, and XPD 1012G>A). PCR was successful with DNA from buccal swabs for 62% to 89% of subjects and from FTA cards for 83% to 100% of subjects, depending on the locus. The matched pair odds ratios (95% confidence interval) comparing success of FTA cards with buccal swabs are as follows: MTHFR 677C>T using PCR-RFLP, 12.5 (11.6-13.5) and using real-time PCR, 130.0 (113.1-152.8); ACE I/D using PCR-amplified fragment length polymorphism, 3.36 (3.2-3.5); XPD 1012G>A using real-time PCR, 150.0 (132.7-172.3). FTA cards are a robust DNA collection method and generally produce DNA suitable for PCR more reliably than buccal swabs. There are, however, technical challenges in handling discs punched from FTA cards that intending users should be aware of.

We devised a simple, noninvasive, cost-efficient technique for collecting buccal cell DNA for molecular epidemiology studies. Subjects (n = 52) brushed their oral mucosa and expectorated the fluid in their mouths, which was applied to "Guthrie" cards pretreated to retard bacterial growth and inhibit nuclease activity (IsoCode, Schleicher and Schuell, Keene, NH). The cards are well-suited for transport and storage because they dry quickly, need no processing, and are compact and lightweight. We stored the samples at room temperature for 5 days to mimic a field situation and then divided them into portions from which DNA was extracted either immediately or after storage for 9 months at room temperature, -20 degrees C, or -70 degrees C. The fresh samples had a median yield of 2.3 microg of human DNA (range, 0.2-53.8 microg), which was adequate for at least 550 PCR reactions. More than 90% of the samples were amplified in all three beta-globin gene fragment assays attempted. DNA extract frozen for 1 week at -20 degrees C also performed well. Stored samples had reduced DNA yields, which achieved statistical significance for room temperature and -70 degrees C, but not -20 degrees C, storage. However, because all of the stored samples tested were successfully amplified, the observed reduction may represent tighter DNA fixation to the card over time rather than loss of genetic material. We conclude that treated cards are an alternative to brushes/swabs and mouth rinses for the collection of buccal cell DNA and offer some advantages over these methods, particularly for large-scale or large-scale or long-term studies involving stored samples and studies in which samples are collected off-site and transported. Future studies that enable direct comparisons of the various buccal cell collection methods are needed.