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Table 2 Predictors of quality control failure among buccal samples

From: Quantitative criteria for improving performance of buccal DNA for high-throughput genetic analysis

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
  1. Mean (95% confidence limits of mean) or n (%) presented; median [interquartile range] presented for years since sample collection.
  2. a Back-transformed from log values (geometric mean).