Table 4.
Comparison of ethanol concentrations in samples of venous and capillary blood using 100 µL aliquots.
| Sample | Mean BAC for 100 μL venous (mg/100 mL) | SD | CV% | Mean BAC for 100 μL capillary (mg/100 mL) | SD | CV% | Difference (mg/100 mL) | Paired t-test p-value |
|---|---|---|---|---|---|---|---|---|
| 1 (M) | 65 | 1.45 | 2.23 | 61 | 1.24 | 2.03 | 4.01 | 0.028 |
| 2 (M) | 74 | 1.33 | 1.79 | 69 | 1.29 | 1.88 | 5.61 | 0.014 |
| 3 (M) | 56 | 0.99 | 1.77 | 51 | 1.90 | 3.76 | 5.09 | 0.028 |
| 4 (F) | 7a | n/a | n/a | 6a | n/a | n/a | n/a | n/a |
| 5 (M) | 57 | 0.37 | 0.65 | 52 | 0.83 | 1.58 | 4.55 | 0.007 |
| 6 (M) | 20 | 0.45 | 2.23 | 14 | 0.58 | 4.11 | 5.95 | 0.000 |
| 7 (M) | 67 | 0.78 | 1.17 | 60 | 1.06 | 1.79 | 7.44 | 0.001 |
| 8 (F) | 26 | 0.60 | 2.33 | 20 | 0.59 | 2.93 | 5.70 | 0.000 |
| 9 (F) | 26 | 0.54 | 2.07 | 21 | 0.35 | 1.71 | 5.48 | 0.000 |
| 10 (M) | 23 | 0.99 | 4.29 | 19 | 0.73 | 3.87 | 4.28 | 0.002 |
| 11 (M) | 19 | 1.28 | 6.63 | 14 | 0.91 | 6.43 | 5.14 | 0.003 |
| 12 (M) | 17 | 1.44 | 8.61 | 11 | 1.05 | 9.19 | 5.29 | 0.000 |
| 13 (M) | 28 | 0.51 | 1.83 | 25 | 1.26 | 4.95 | 2.16 | 0.094 |
| 14 (M) | 31 | 1.12 | 3.60 | 29 | 1.46 | 5.10 | 2.46 | 0.034 |
| 15 (M) | 19 | 2.17 | 11.48 | 20 | 0.09 | 4.48 | –1.01 | 0.552 |
| 16 (M) | 27 | 1.29 | 4.81 | 25 | 1.35 | 5.36 | 1.65 | 0.000 |
| 17 (M) | 25 | 0.81 | 3.24 | 23 | 1.06 | 4.57 | 1.85 | 0.036 |
| 18 (M) | 29 | 1.16 | 4.01 | 26 | 0.78 | 2.99 | 2.83 | 0.075 |
| 19 (M) | 25 | 0.97 | 3.81 | 21 | 0.13 | 0.63 | 4.64 | 0.114 |
| 20 (F) | 31 | 1.42 | 4.62 | 29 | 0.35 | 1.19 | 1.44 | 0.251 |
| 21 (M) | 25 | 1.55 | 6.19 | 22 | 0.65 | 2.98 | 3.34 | 0.037 |
| 22 (M) | 64 | 0.37 | 0.58 | 61 | 0.07 | 0.11 | 2.83 | 0.012 |
| 23 (M) | 58 | 1.11 | 1.90 | 54 | 0.00 | 0.02 | 4.30 | 0.012 |
| 24 (M) | 67 | 1.02 | 1.52 | 62 | 0.56 | 0.90 | 5.07 | 0.096 |
| 25 (M) | 59 | 1.22 | 2.07 | 54 | 0.71 | 1.33 | 5.15 | 0.019 |
| 26 (M) | 76 | 0.70 | 0.92 | 71 | 0.89 | 1.25 | 5.06 | 0.008 |
| 27 (M) | 72 | 0.84 | 1.17 | 73 | 0.67 | 0.91 | –0.93 | 0.332 |
| 28 (M) | 42 | 1.88 | 4.44 | 39 | 2.34 | 5.95 | 3.04 | 0.082 |
| 29 (M) | 64 | 2.33 | 3.66 | 58 | 1.71 | 2.98 | 6.10 | 0.006 |
| 30 (M) | 64 | 1.41 | 2.20 | 61 | 0.70 | 1.15 | 3.17 | 0.014 |
| 31 (M) | 63 | 2.26 | 3.58 | 61 | 3.56 | 5.83 | 2.01 | 0.524 |
| 32 (F) | 32 | 1.92 | 6.07 | 29 | 1.11 | 3.83 | 2.53 | 0.010 |
| 33 (M) | 21 | 1.01 | 4.74 | 21 | 0.49 | 2.38 | 0.69 | 0.361 |
| 34 (M) | 73 | 0.46 | 0.63 | 68 | 0.94 | 1.38 | 4.74 | 0.002 |
| 35 (M) | 31 | 0.27 | 0.84 | 30 | 0.77 | 2.53 | 0.96 | 0.204 |
| 36 (M) | 21 | 0.55 | 2.60 | 20 | 0.22 | 1.09 | 1.20 | 0.013 |
| 37 (F) | 35 | 0.22 | 0.63 | 33 | 0.36 | 1.11 | 2.73 | 0.102 |
| 38 (M) | 65 | 0.88 | 1.34 | 65 | 0.99 | 1.53 | 0.58 | 0.766 |
| 39 (M) | 63 | 1.22 | 1.93 | 60 | 1.06 | 1.75 | 2.80 | 0.128 |
| 40 (M) | 36 | 1.06 | 2.97 | 32 | 0.83 | 2.58 | 3.42 | 0.015 |
Our results indicate that capillary and venous blood provide differing BAC values and cannot be treated as equivalent matrices. In approximately 92.5% of samples, the corresponding capillary BAC was on average 3.38 mg/100 mL lower than the venous equivalent.
aValue was below the limit of quantitation of the method.