Table 2

Predictors of quality control failure among buccal samples
N All buccal QC passed QC failed P-value t-test or χ2 p-value Wilcoxon or Exact
708 628 80
Years since sample collection 7.9 [5.3, 10.0] 8.0 [5.6, 10.0] 5.3 [4.2, 9.0] <0.0001 <0.0001
Current cigarette smoker (%) 136 (19.2%) 116 (18.5%) 20 (25%) 0.16 0.18
Current cigar smoker (%) 21 (3%) 17 (2.7%) 4 (5%) 0.26 0.28
Average daily coffee intake (cups) 1.43 (1.28, 1.59) 1.39 (1.23, 1.54) 1.79 (1.16, 2.42) 0.23 0.25
Average daily tea intake (cups) 0.42 (0.33, 0.51) 0.42 (0.32, 0.51) 0.42 (0.19, 0.66) 0.96 0.77
Average daily sodas 0.75 (0.62, 0.87) 0.74 (0.60, 0.87) 0.85 (0.54, 1.16) 0.50 0.06
260/280 Ratio 1.81 (1.80-1.81) 1.81 (1.80-1.81) 1.82(1.80-1.84) 0.42 0.32
260/230 Ratio 1.17 (1.15- 1.20) 1.18 (1.15-1.21) 1.14 (1.06-1.21) 0.38 0.39
Total DNA (ng/μl)a 87.4 (82.3-92.8) 85.6 (80.6-91.8) 102.5 (87.4-121.5) 0.06 0.05
ds DNA (ng/μl)a 55.7 (52.5-59.1) 56.8 (53.5-60.3) 49.4 (41.3-59.1) 0.12 0.09
ds/total DNA ratio 0.66 (0.65-0.68) 0.68 (0.67-0.69) 0.52 (0.46-0.57) <0.0001 <0.0001

Mean (95% confidence limits of mean) or n (%) presented; median [interquartile range] presented for years since sample collection.

a Back-transformed from log values (geometric mean).

Woo et al.

Woo et al. BMC Genetics 2012 13:75   doi:10.1186/1471-2156-13-75

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