Comparison of methods for collection of DNA samples by mail in the black womenʹs health study

Purpose The authors compared approaches to participants and methods of collecting buccal cell samples by mail in the Black Womenʹs Health Study, a follow-up study of geographically dispersed African-American women. Outcomes of interest were within group participation rates, yield of DNA, and PCR success. Methods Six hundred fifty six participants were randomized to four groups: Groups 1 and 2 used the cheek swab method and Groups 3 and 4 used the mouthwash swish method. Groups 1 and 3 were mailed collection kits together with consent forms, whereas Groups 2 and 4 were mailed a kit only after returning a signed consent. Results Participation rates were similar regardless of the method used for sample collection or mailing of the kits: samples were returned by 40% of Group 1, 37% of Group 2, 36% of Group 3, and 35% of Group 4. The median DNA yield was 3693 ng/sample for the swab method and 10,077 ng/sample for the mouthwash swish method (p<0.001). PCR analyses were successful in 98% of mouthwash samples and 94% of swab samples. Conclusion Because of its higher yield of DNA, the mouthwash swish method is preferable for collection of buccal cell samples by mail.