There have been reports of false-positive ethanol concentrations in blood samples tested by enzymatic assays. Subsequent studies have yielded contradictory results.
An enzymatic assay for ethanol involves:
(1) oxidation of ethyl alcohol to acetaldehyde with concurrent reduction of NAD to NADH
(2) production of NADH is measured at an absorbance of 340 nm
The argument is that elevated lactate and LDH in blood can impact this measurement. Nine et al linked the interference to coenzyme depletion.
Some of the claims of a false-positive assay have involved lawsuits related to traffic accidents.
Lefrere et al states that the interference is due to matrix effect and can be observed in post-mortem specimens. Ultracentrifugation of a "positive" urine sample from an infant resulted in a negative ethanol result.
Observations:
(1) The gold standard for blood ethanol determination is gas chromatography. If an enzymatic result is in doubt, then a specimen should be sent for gas chromatography.
(2) To make the argument the suspected sample should have an elevated lactate and LDH.
(3) If the reported ethanol concentration is incongruous with the clinical situation, then the result should be investigated.
