Table 5.
Comparison of ethanol concentrations in samples of venous and capillary blood using 10 µL aliquots.
| Sample | Mean BAC for 10 μL venous (mg/100 mL) | SD | CV% | Mean BAC for 10 μL capillary (mg/100 mL) | SD | CV% | Difference (mg/100 mL) | Paired t-test p-value |
|---|---|---|---|---|---|---|---|---|
| 1 (M) | 64 | 2.29 | 3.56 | 60 | 1.62 | 2.69 | 4.05 | 0.168 |
| 2 (M) | 75 | 1.07 | 1.43 | 67 | 1.67 | 2.51 | 8.05 | 0.015 |
| 3 (M) | 56 | 2.20 | 3.9 | 48 | 0.54 | 1.12 | 8.23 | 0.007 |
| 4 (F) | n/aa | n/a | n/a | n/a | n/a | n/a | n/a | n/a |
| 5 (M) | 58 | 0.72 | 1.24 | 55 | 1.23 | 2.25 | 3.07 | 0.044 |
| 6 (M) | 20 | 0.23 | 1.12 | 15 | 0.34 | 2.23 | 5.08 | 0.000 |
| 7 (M) | 55 | 0.68 | 1.24 | 44 | 0.58 | 1.33 | 10.94 | 0.000 |
| 8 (F) | 27 | 1.26 | 4.65 | 21 | 0.48 | 2.31 | 6.31 | 0.002 |
| 9 (F) | 27 | 0.45 | 1.67 | 21 | 0.27 | 1.30 | 6.02 | 0.000 |
| 10 (M) | 21 | 0.52 | 2.45 | 16 | 0.65 | 4.00 | 5.03 | 0.000 |
| 11 (M) | 19 | 0.92 | 4.86 | 12 | 0.72 | 6.30 | 7.35 | 0.008 |
| 12 (M) | 16 | 0.72 | 4.64 | 9* | 0.84 | 9.01 | 6.14 | 0.000 |
| 13 (M) | 28 | 0.79 | 2.87 | 26 | 1.88 | 7.33 | 1.93 | 0.061 |
| 14 (M) | 30 | 1.22 | 4.05 | 27 | 1.24 | 4.59 | 3.27 | 0.000 |
| 15 (M) | 19 | 0.55 | 2.91 | 19 | 0.50 | 2.69 | 0.23 | 0.647 |
| 16 (M) | 27 | 0.73 | 2.68 | 24 | 0.96 | 4.03 | 3.43 | 0.008 |
| 17 (M) | 26 | 1.07 | 4.17 | 23 | 0.88 | 3.90 | 2.97 | 0.037 |
| 18 (M) | 29 | 1.17 | 4.03 | 24 | 1.58 | 6.57 | 4.94 | 0.047 |
| 19 (M) | 23 | 0.97 | 4.25 | 21 | 1.34 | 6.46 | 2.11 | 0.094 |
| 20 (F) | 30 | 0.07 | 0.25 | 27 | 1.09 | 4.10 | 3.02 | 0.052 |
| 21 (M) | 27 | 1.04 | 3.87 | 21 | 1.24 | 5.84 | 5.65 | 0.013 |
| 22 (M) | 62 | 0.74 | 1.19 | 57 | 0.99 | 1.75 | 5.18 | 0.014 |
| 23 (M) | 52 | 1.11 | 2.13 | 51 | 1.83 | 3.60 | 1.55 | 0.382 |
| 24 (M) | 62 | 0.70 | 1.13 | 60 | 0.54 | 0.90 | 2.17 | 0.039 |
| 25 (M) | 58 | 1.01 | 1.74 | 52 | 0.85 | 1.63 | 5.91 | 0.008 |
| 26 (M) | 74 | 1.41 | 1.89 | 69 | 2.11 | 3.08 | 5.74 | 0.006 |
| 27 (M) | 73 | 1.88 | 2.60 | 71 | 0.91 | 1.29 | 1.53 | 0.407 |
| 28 (M) | 43 | 0.68 | 1.57 | 41 | 1.58 | 3.83 | 2.16 | 0.106 |
| 29 (M) | 62 | 1.13 | 1.81 | 58 | 0.48 | 0.84 | 4.24 | 0.043 |
| 30 (M) | 67 | 2.81 | 4.18 | 64 | 1.02 | 1.59 | 2.96 | 0.148 |
| 31 (M) | 65 | 1.16 | 1.80 | 59 | 1.49 | 2.50 | 5.18 | 0.024 |
| 32 (F) | 33 | 0.79 | 2.36 | 30 | 2.03 | 6.84 | 3.63 | 0.038 |
| 33 (M) | 20 | 0.59 | 2.88 | 19 | 0.52 | 2.74 | 1.48 | 0.088 |
| 34 (M) | 72 | 1.02 | 1.41 | 67 | 0.33 | 0.48 | 4.91 | 0.032 |
| 35 (M) | 30 | 0.09 | 0.30 | 29 | 0.17 | 0.60 | 1.33 | 0.129 |
| 36 (M) | 18 | 1.15 | 6.33 | 18 | 0.75 | 4.26 | 0.55 | 0.513 |
| 37 (F) | 35 | 0.34 | 0.97 | 28 | 1.06 | 3.78 | 6.46 | 0.089 |
| 38 (M) | 66 | 0.68 | 1.03 | 60 | 0.84 | 1.39 | 6.14 | 0.095 |
| 39 (M) | 62 | 1.14 | 1.83 | 57 | 1.58 | 2.75 | 5.00 | 0.243 |
| 40 (M) | 33 | 0.96 | 2.92 | 30 | 0.26 | 0.89 | 3.23 | 0.032 |
Our results indicate that micro-analyses of capillary and venous blood provide differing BAC values and cannot be treated as equivalent matrices. In approximately 97.5% of samples, the corresponding capillary BAC was on average 4.13 mg/100 mL lower than the venous equivalent.
aValue was below the limit of quantitation of the method.