The enzymatic analysis of alcohol (ethanol) in serum and plasma with the alcohol dehydrogenase reagent: focus on intra-analytical and post-analytical aspects.

The alcohol dehydrogenase (ADH) method is commonly used to measure serum alcohol concentration (SAC) and plasma alcohol concentration (PAC) for the rapid detection of ethanol intoxication in emergency medical departments. Alcohol dehydrogenase methods are sometimes used in forensic laboratories as a preliminary screening test prior to confirmation by gas chromatographic (GC) methods. This review identifies critical factors affecting results of ADH methods of analysis including clinical reliability and forensic defensibility. Key considerations include intra-analytical factors (method chemistry, calibration, analytical performance, interferences, calibrator stability, and sample matrix effects) and post-analytical factors (measurement units, reference ranges, performance specifications, uncertainty budget, medical decision levels, legal intoxication thresholds, ADH-GC agreement, and SAC/PAC to blood alcohol concentration (BAC) conversion). The yeast ADH method demonstrates high selectivity for ethanol with no assay-specific bias, and measurement error and uncertainty meet regulatory standards. However, ADH methods are prone to interferences, particularly from lactate dehydrogenase/lactic acid (LD/LA), leading to potential false positive results. Free hemoglobin (hemolysis) is another problem with ADH methods introducing a negative bias. When results provided by hospital laboratories are interpreted in a legal context, care is needed because ethanol concentrations in plasma/serum are about 15% higher than in whole blood (range 10-20%). Although less important in clinical practice, these differences are important to consider in a forensic context. The ADH method is not inherently a forensic assay, but these limitations can be mitigated by refining laboratory procedures and standardizing the assay methodology and quality control, thus strengthening forensic reliability and boosting confidence in the analytical results.