Lindberg Lars, Grubb David, Dencker Daniel, Finnhult Mikael, Olsson Sven-Gunnar
Lund University, Department of Clinical Sciences (Anaesthesia and Intensive Care, PICU), Skane University Hospital in Lund, SE-221 85 Lund, Sweden.
Lund University, Department of Clinical Sciences (Anaesthesia and Intensive Care, PICU), Skane University Hospital in Lund, SE-221 85 Lund, Sweden.
Forensic Sci Int. 2015 Apr;249:66-72. doi: 10.1016/j.forsciint.2015.01.017. Epub 2015 Jan 30.
The presence of mouth alcohol (MA) during alcohol breath test for law enforcement is the most common cause of falsely high breath alcohol concentrations (BrAC). A fast and reliable test for detection of MA roadside at the scene of the act would facilitate the police efforts for proper prosecution. A tentative technique to use orally exhaled water vapour as a reference gas to position the origin of alcohol was validated. BrAC and water vapour concentration (WVC) were simultaneously measured as a known MA component was added to subjects with existing blood alcohol. In the absence of MA, water always precedes alcohol in a volumetric expirogram. In the presence of MA this relationship reversed. A scatterplot of WVC versus BrAC from similar fractional exhaled volumes illustrates how their relative positions change by MA. A deviation area (DA) between the scatterplot curve and a fictitious linear relationship was defined as a measurement of MA. The accuracy and cut-off level of the DA to detect MA were determined with receiver operating characteristic (ROC) curve analysis. The area under the ROC curve (AUC) was 0.95 (95% CI 0.90-1.0), indicating excellent discriminatory ability. The optimal cut-off for DA to discriminate between MA ≥0.010 mg/L (1 μg/100 ml, 0.002 g/210 L) or lack of MA was -0.35, with a sensitivity of 0.91 and specificity of 0.95. Analysis of BrAC in relation to WVC is a practical method to detect and confirm MA contamination with high reliability.
在执法过程中进行酒精呼气测试时，口腔酒精（MA）的存在是导致呼气酒精浓度（BrAC）出现假高值的最常见原因。一种能够在现场快速可靠地检测路边MA的测试方法将有助于警方进行适当的起诉工作。一种尝试性的技术得到了验证，即使用口腔呼出的水蒸气作为参考气体来确定酒精的来源。在向已有血液酒精含量的受试者添加已知MA成分的同时，同步测量BrAC和水蒸气浓度（WVC）。在没有MA的情况下，在体积呼气图中，水总是先于酒精呼出。在有MA的情况下，这种关系发生了逆转。来自相似呼出分数体积的WVC与BrAC的散点图说明了MA如何改变它们的相对位置。散点图曲线与虚拟线性关系之间的偏差区域（DA）被定义为MA的一种测量指标。通过受试者工作特征（ROC）曲线分析确定了DA检测MA的准确性和临界水平。ROC曲线下面积（AUC）为0.95（95%可信区间0.90 - 1.0），表明具有出色的区分能力。DA区分MA≥0.010 mg/L（1 μg/100 ml，0.002 g/210 L）或无MA的最佳临界值为 - 0.35，灵敏度为0.91，特异性为0.95。分析与WVC相关的BrAC是一种检测和确认MA污染的实用方法，具有很高的可靠性。
