Ethanol

Clinical utility

Ethanol is the most widely used and abused chemical substance, and its measurement is one of the more frequently performed tests in the toxicology laboratory. Quantitative blood/serum ethanol is used in emergency settings to help explain altered mental status, coma, or hypoglycemia and to determine whether it is contributing to an increased osmolal gap alongside other toxic alcohols. It underlies forensic and legal determinations such as statutory driving limits, and ethanol itself is also used therapeutically as a competitive alcohol dehydrogenase inhibitor in methanol or ethylene glycol poisoning. Ethanol biomarkers (EtG, EtS, PEth) are additionally used clinically and legally to detect recent or heavy drinking beyond the short window of direct ethanol measurement.

Alcohol Intoxication

How it's measured

Enzymatic assay (serum, plasma, whole blood, urine, oral fluid)

Enzymatic analysis is the method of choice for ethanol in most clinical laboratories. Alcohol dehydrogenase (ADH) is reasonably specific for ethanol (interference from isopropanol, acetone, methanol, and ethylene glycol is typically <1%), and the reaction is followed by the increase in absorbance of NADH at 340 nm:

Ethanol + NAD+ --alcohol dehydrogenase (ADH)--> Acetaldehyde + NADH + H+

Serum or plasma is most common, but the method also performs well with urine or oral fluid; whole blood can be assayed directly or after a precipitation step to avoid hemoglobin interference. A recognized interferent is high blood lactate together with elevated lactate dehydrogenase (LDH), via the coupled reaction:

Lactate + NAD+ --lactate dehydrogenase (LDH)--> Pyruvate + NADH + H+

since the NADH generated by this side reaction can be mistaken for ethanol-derived signal in susceptible assays.

Gas chromatography

Development of gas chromatographic methods for volatile alcohols in 1964 was a key advance in alcohol/toxic-alcohol testing. Flame ionization GC remains the most common method for detection and quantitation of volatile alcohols (ethanol, methanol, isopropanol, acetone) in biological samples, distinguishing among them and measuring concentrations as low as 10 mg/dL (0.01%). Specimens are prepared by direct injection (diluted with an aqueous internal standard) or by headspace analysis, which exploits the principle that the amount of volatile alcohol in the air space above a liquid sample is proportional to its concentration in solution. GC results generally compare closely with those from enzymatic assays.

Breath alcohol analysis

Because blood collection is invasive, breath testing (based on near-instantaneous equilibration of alcohol between alveolar air and capillary blood, conventionally at a ratio of about 2100:1, though possibly closer to 2300:1) has become the mainstay of evidential and point-of-care alcohol measurement. A 15-minute deprivation period before testing, and duplicate measurements 5–10 minutes apart, are used to guard against residual mouth alcohol contamination. Breath analyzers use one of several measurement principles: infrared absorption spectrometry (most common), dichromate-sulfuric acid oxidation-reduction (photometric), gas chromatography (flame ionization or thermal conductivity detection), electrochemical (fuel cell) oxidation, or metal oxide semiconductor sensors.

Ethanol biomarkers

Ethyl glucuronide (EtG) and ethyl sulfate (EtS), phase II conjugates of ethanol measured in urine, and phosphatidylethanol (PEth), formed in whole blood by phospholipase D in the presence of ethanol, serve as biomarkers of ethanol exposure with much longer detection windows than direct ethanol assays (EtG up to about 80 hours; PEth up to about 3 weeks), and are used to monitor recent or heavy/binge drinking in clinical and legal settings.

Sources: Ch43 Clinical toxicology.pdf · Extracted 2026-08-18 · Approved 2026-08-25

Method comparison

Ortho VITROS 4600

kinetics endpoint λ 340 nm AMR 10–300 mg/dL (2.2–65.1 mmol/L; 0.1–3.0 g/L)

ethanol + NAD+ --ADH--> acetaldehyde + NADH
acetaldehyde + TRIS --> acetaldehyde-TRIS complex

Endpoint colorimetric (reflectance) dry-slide assay; NADH formation is the species measured, not ethanol or acetaldehyde directly.

Spreading layer — Spreading layer (sample distribution layer): Barium sulfate (BaSO4) matrix containing nicotinamide adenine dinucleotide (NAD+), approximately 0.8 mg/cm2
Reagent layer — Reagent layer (reaction layer): Alcohol dehydrogenase (yeast), approximately 1.1 U/cm2; TRIS (tris(hydroxymethyl)aminomethane) buffer, pH 8.75, approximately 1.0 mg/cm2

Reaction procedure:

A drop of patient serum/plasma sample is deposited on the VITROS ALC slide; the spreading layer (BaSO4, containing NAD+) evenly distributes the sample down to the underlying reagent layer.
In the reagent layer, alcohol dehydrogenase oxidizes ethanol in the sample to acetaldehyde, reducing the NAD+ carried down from the spreading layer to NADH.
TRIS buffer (pH 8.75) in the reagent layer binds the acetaldehyde as it forms, producing an acetaldehyde-TRIS complex; removing acetaldehyde from solution drives the reversible ADH reaction to completion so that NADH accumulation reflects the full ethanol content rather than stalling at an equilibrium point.
After a fixed 5-minute incubation at 37°C, the slide's reflectance density at 340 nm (proportional to the NADH generated) is read once and converted to an ethanol concentration using the software-resident endpoint colorimetric math model referenced to slide-lot calibration.

Reaction notes:
This is an endpoint (fixed-time) colorimetric reaction, not a rate assay. NAD+ is the stoichiometric cofactor reduced 1:1 with ethanol oxidized; the insert states fixed mass/activity amounts per cm2 (ADH 1.1 U, NAD+ 0.8 mg, TRIS 1.0 mg) but not molar concentrations, so an exact molar excess cannot be derived from the insert alone. TRIS's role is not to generate signal but to trap the acetaldehyde product as it forms, pulling the reversible ADH reaction to completion (mass-action/Le Chatelier effect) so the fixed-time NADH signal approximates total ethanol converted. The species actually monitored is NADH (reflectance at 340 nm), not ethanol or acetaldehyde directly.
Kinetics: A single reflectance reading is taken after a fixed 5-minute incubation at 37°C (endpoint, not rate/kinetic); concentration is derived from a software-resident endpoint colorimetric math model referenced to slide-lot calibration. This supports the stated linear reportable range of 10–300 mg/dL (2.2–65.1 mmol/L); samples above this range must be diluted and reanalyzed rather than read as-is.
Readout: Reflectance density at 340 nm, generated by NADH accumulated in the reagent layer, is read once at the end of the fixed incubation and converted to an ethanol concentration via the current slide-lot calibration curve.
What's measured: Measures ethanol in serum/plasma via ADH-catalyzed oxidation. Because ADH is not absolutely specific for ethanol, other low-molecular-weight alcohols that are also ADH substrates (n-propanol, isopropanol, n-butanol, ethylene glycol) will cross-react and generate a positive ethanol result in the absence of true ethanol; acetaldehyde, acetone, and methanol were specifically tested and do not cross-react.
Interference implications: Metronidazole (tested at 12.5 and 25 mg/dL) and methotrexate (45.4 mg/dL) each produce small, quantified positive biases (+8 to +19 mg/dL and +11.0 mg/dL, respectively) at the ethanol concentrations tested. Structurally related alcohols cross-react as alternate ADH substrates, with bias scaling roughly with how good an ADH substrate each is: n-propanol (+108 mg/dL) > n-butanol (+58 mg/dL) > isopropanol (+20 mg/dL) > ethylene glycol (+4.0 mg/dL), all tested at 200 mg/dL interferent. Postmortem or immediately antemortem specimens can give false-positive results from extremely high endogenous LDH/lactate and should be confirmed by GC. Outside of these, an extensive panel of over 100 drugs, metabolites, and physiologic substances (e.g., acetaminophen, salicylate, bilirubin, hemoglobin up to 1000 mg/dL, triglyceride up to 1600 mg/dL, lipemia/Intralipid, total protein) was tested per NCCLS EP7 and validated as non-interfering (bias <11 mg/dL) at the concentrations shown.
Known bias: Method comparison studies reported in the insert show good agreement with Headspace Gas Chromatography (VITROS 750 vs. GC: slope 1.03, r=0.998, n=64) and with a commercial ADH-based method (VITROS 750 vs. commercial method: slope 0.92, r=0.990, n=187), as well as good cross-platform agreement among VITROS systems (slopes 0.98–1.00, r≥0.998).

Interferences & pre-/post-analytical notes

Interferences

Known interferences

Postmortem/immediately antemortem specimen (endogenous LDH and lactate): may produce false positive ethanol results because of extremely high levels of lactate dehydrogenase and lactate; confirm positive results by gas chromatography (GC)
Metronidazole: positive bias +8 mg/dL (1.7 mmol/L) at ethanol 95 mg/dL when present at 12.5 mg/dL; +19 mg/dL (4.1 mmol/L) at ethanol 95 mg/dL when present at 25 mg/dL (12.5 mg/dL (0.73 mmol/L) and 25 mg/dL (1.46 mmol/L)) — NCCLS Protocol EP7 (ref. 11)
Methotrexate: positive bias +11.0 mg/dL (2.4 mmol/L) at ethanol 98 mg/dL (45.4 mg/dL (1.0 mmol/L)) — NCCLS Protocol EP7 (ref. 11)
Ethylene glycol: cross-reacts as an ADH substrate; positive bias +4.0 mg/dL (0.87 mmol/L) (200 mg/dL (32.22 mmol/L))
n-Propanol: cross-reacts as an ADH substrate; positive bias +108 mg/dL (23.44 mmol/L) (200 mg/dL (33.28 mmol/L))
Isopropanol: cross-reacts as an ADH substrate; positive bias +20 mg/dL (4.34 mmol/L) (200 mg/dL (33.28 mmol/L))
n-Butanol: cross-reacts as an ADH substrate; positive bias +58 mg/dL (12.59 mmol/L) (200 mg/dL (26.98 mmol/L))

Validated -- no significant interference

Acetaldehyde: no significant interference; bias <11 mg/dL (<2.4 mmol/L) (10 mg/dL (2 mmol/L)) — NCCLS Protocol EP7 (ref. 11)
Acetaminophen: no significant interference (20 mg/dL (1 mmol/L))
Acetate: no significant interference (50 mmol/L)
Acetone: no significant interference (450 mg/dL (77 mmol/L))
Acyclovir: no significant interference (10 mg/dL (444 μmol/L))
Albuterol sulfate: no significant interference (18 μg/dL (375 nmol/L))
Allopurinol: no significant interference (20 mg/dL (1 mmol/L))
Amitriptyline: no significant interference (1 mg/dL (36 μmol/L))
Ammonia: no significant interference (0.5 mmol/L)
Amphotericin B: no significant interference (35 μg/mL (38 μmol/L))
Ampicillin: no significant interference (200 mg/dL (6 mmol/L))
Ascorbic Acid: no significant interference (6 mg/dL (341 μmol/L))
Atenolol: no significant interference (2 mg/dL (75 μmol/L))
Azathioprine: no significant interference (1 mg/dL (36 μmol/L))
Benzalkonium chloride: no significant interference (10 mg/dL (314 μmol/L))
7.5% Betadine: no significant interference (20 μL/dL)
Bicarbonate: no significant interference (40 mmol/L)
Bilirubin: no significant interference (40 mg/dL (684 μmol/L))
2,3-Butanediol: no significant interference (3.5 mmol/L)
2-Butanone: no significant interference (3.5 mmol/L)
Captopril: no significant interference (2 mg/dL (92 μmol/L))
Carbamazepine: no significant interference (12 mg/dL (508 μmol/L))
Cefazolin: no significant interference (400 mg/dL (9 mmol/L))
Ceftriaxone: no significant interference (250 mg/dL (5 mmol/L))
Chloral hydrate: no significant interference (10 mg/dL (605 μmol/L))
Chloramphenicol: no significant interference (25 mg/dL (774 μmol/L))
Chloride: no significant interference (170 mmol/L)
Chlorpromazine: no significant interference (1 mg/dL (31 μmol/L))
Cholesterol: no significant interference (405 mg/dL (10 mmol/L))
Cholic acid: no significant interference (6 μmol/L)
Cimetidine: no significant interference (8 mg/dL (317 μmol/L))
Clonidine: no significant interference (37 μg/dL (2 μmol/L))
Codeine: no significant interference (1.7 mg/dL (58 μmol/L))
Cytarabine: no significant interference (120 mg/dL (5 mmol/L))
Desipramine: no significant interference (1 mg/dL (38 μmol/L))
Dexamethazone: no significant interference (1.35 μg/mL (3 μmol/L))
Dextran 40: no significant interference (3000 mg/dL (1 mmol/L))
Diazepam: no significant interference (2 mg/dL (70 μmol/L))
Diethyldithiocarbamate: no significant interference (2.3 mg/dL (155 μmol/L))
Digoxin: no significant interference (30 μg/dL (384 nmol/L))
Diltiazem: no significant interference (0.2 mg/dL (5 μmol/L))
Dipyrone: no significant interference (250 mg/dL (9 mmol/L))
Disulfiram: no significant interference (0.8 mg/dL (27 μmol/L))
Dopamine: no significant interference (30 μg/dL (2 μmol/L))
Doxepin: no significant interference (2 mg/dL (72 μmol/L))
Doxorubicin: no significant interference (0.6 μg/mL (1 μmol/L))
Erythromycin: no significant interference (20 mg/dL (273 μmol/L))
Ferrous gluconate: no significant interference (300 μg/dL (54 μmol/L))
Fluoxetine: no significant interference (1 mg/dL (32 μmol/L))
Formaldehyde: no significant interference (35 mg/dL (12 mmol/L))
Formic acid: no significant interference (450 mg/dL (98 mmol/L))
Furosemide: no significant interference (10 mg/dL (302 μmol/L))
Geneticin disulfate: no significant interference (50 mg/dL (1 mmol/L))
Gentamicin: no significant interference (12 mg/dL (256 μmol/L))
Gentisic Acid: no significant interference (25 mg/dL (2 mmol/L))
Glyburide: no significant interference (6.4 μg/dL (130 nmol/L))
Glycerol: no significant interference (1 mmol/L)
Glycolic acid: no significant interference (700 mg/dL (92 mmol/L))
Glyoxylic acid: no significant interference (5 mg/dL (675 μmol/L))
Haloperidol: no significant interference (0.2 mg/dL (5 μmol/L))
Hemoglobin: no significant interference (1000 mg/dL (10 g/L))
Hydrochlorothiazide: no significant interference (2 mg/dL (67 μmol/L))
Hydroxychloroquine: no significant interference (1 mg/dL (30 μmol/L))
Hydroxyurea: no significant interference (0.1 mg/dL (13 μmol/L))
Hydroxyzine: no significant interference (0.1 mg/dL (3 μmol/L))
Hypaque: no significant interference (500 mg/dL (8 mmol/L))
Ibuprofen: no significant interference (40 mg/dL (2 mmol/L))
Imipramine: no significant interference (1 mg/dL (36 μmol/L))
Intralipid: no significant interference (800 mg/dL (8 g/L))
Isoniazid: no significant interference (7 mg/dL (511 μmol/L))
Keflin: no significant interference (0.6 mg/dL (15 μmol/L))
L-Dopa: no significant interference (30 mg/dL (2 mmol/L))
Lactic Acid: no significant interference (176 mg/dL (20 mmol/L))
Lactose: no significant interference (3000 mg/dL (88 mmol/L))
Lactulose: no significant interference (6.5 mg/dL (190 μmol/L))
Lecithin (phospholipids): no significant interference (500 mg/dL (5 g/L))
Lidocaine: no significant interference (6 mg/dL (256 μmol/L))
Streptokinase: no significant interference (700 U/mL)
Lithium: no significant interference (3.5 mg/dL (825 μmol/L))
Streptomycin: no significant interference (50 mg/dL (439 μmol/L))
Lovastatin: no significant interference (0.06 mg/dL (1 μmol/L))
Theophylline: no significant interference (25 mg/dL (1 mmol/L))
Mannitol: no significant interference (650 mg/dL (36 mmol/L))
Thimerosal: no significant interference (100 mg/dL (2 mmol/L))
Metoprolol: no significant interference (0.3 mg/dL (11 μmol/L))
Thioridazine: no significant interference (2 mg/dL (54 μmol/L))
Methadone: no significant interference (1 mg/dL (32 μmol/L))
Tolazamide: no significant interference (55 mg/dL (2 mmol/L))
Methanol: no significant interference (700 mg/dL (218 mmol/L))
Total Protein: no significant interference (4 g/dL (40 g/L))
N-Acetylcysteine: no significant interference (100 mg/dL (6 mmol/L))
Total Protein: no significant interference (10 g/dL (100 g/L))
Naproxen: no significant interference (120 mg/dL (5 mmol/L))
Triamterene: no significant interference (6 mg/dL (237 μmol/L))
Neomycin: no significant interference (20 mg/dL (325 μmol/L))
1,1,1-Trichloroethane: no significant interference (72 mg/dL (5 mmol/L))
Nifedipine: no significant interference (1 mg/dL (29 μmol/L))
Triglyceride: no significant interference (1600 mg/dL (181 mmol/L))
Nortriptyline: no significant interference (1 mg/dL (38 μmol/L))
Trimethoprim: no significant interference (25 mg/dL (861 μmol/L))
Nystatin: no significant interference (100 mg/dL (1 mmol/L))
D-Penicillamine: no significant interference (4 mg/dL (268 μmol/L))
Valproic acid: no significant interference (50 mg/dL (3 mmol/L))
Warfarin: no significant interference (10 mg/dL (324 μmol/L))
Sample pH (low): no significant interference (pH 6.9)
Zephiran chloride: no significant interference (1 μL/mL)
Sample pH (high): no significant interference (pH 8.9)
Phenylpropanolamine: no significant interference (0.18 mg/dL (12 μmol/L))
Pseudoephedrine: no significant interference (0.6 mg/dL (36 μmol/L))
Phenelzine: no significant interference (0.25 mg/dL (18 μmol/L))
Phenobarbital: no significant interference (15 mg/dL (646 μmol/L))
Phenylbutazone: no significant interference (100 mg/dL (3 mmol/L))
Phenytoin: no significant interference (30 mg/dL (1 mmol/L))
Prednisone: no significant interference (0.1 mg/dL (3 μmol/L))
Procainamide: no significant interference (20 mg/dL (850 μmol/L))
Promethazine: no significant interference (1 mg/dL (35 μmol/L))
Propranolol: no significant interference (0.5 mg/dL (19 μmol/L))
Propylene glycol: no significant interference (200 mg/dL (26 mmol/L))
Pyruvate: no significant interference (2 mg/dL (230 μmol/L))
Quinidine: no significant interference (5 mg/dL (154 μmol/L))
Ranitidine: no significant interference (15 mg/dL (478 μmol/L))
Salicylate: no significant interference (50 mg/dL (4 mmol/L))
Suramin: no significant interference (100 mg/dL (777 μmol/L))

Pre-analytical

Recommended specimens: serum; plasma (heparin or fluoride oxalate). Not recommended: serum or plasma preserved with mercuric chloride.
Do not cleanse the venipuncture/draw site with alcohol or other volatile disinfectants; use only aqueous disinfectants to avoid contaminating the sample with exogenous ethanol.
Monitor and eliminate alcohol from all outside sources prior to collection/testing.
Handle and store specimens in tightly stoppered containers with minimal dead air space to avoid contamination and evaporation of the volatile analyte; use a freshly filled cup if a test must be repeated.
Mix samples by gentle inversion and bring to room temperature (18–28°C) prior to analysis.
Specimen stability: room temperature (18–28°C) ≤2 days; refrigerated (2–8°C) ≤2 weeks; frozen (≤-18°C) at least one month.
Postmortem or immediately antemortem specimens may produce false positive results because of extremely high endogenous lactate dehydrogenase and lactate.

Post-analytical

If the ethanol result exceeds the measuring range (10–300 mg/dL), dilute and reanalyze: on-analyzer dilution uses VITROS FS Diluent Pack 2 (VITROS 5600/XT7600/4600) or VITROS 7% BSA (VITROS 250/350/XT3400); for manual dilution, dilute the sample with VITROS 7% BSA (an initial twofold dilution is recommended), reanalyze, and multiply the result by the dilution factor.
Positive results obtained on postmortem or immediately antemortem specimens should be confirmed by gas chromatography (GC).

Source: package insert (PDF, Cat #804 6872, rev 13.0) · Extracted 2026-08-25 · Approved 2026-08-26

Roche Cobas c503

kinetics other λ 340 / 700 nm AMR 2.2-108 mmol/L (0.101-4.98 g/L, 10.1-498 mg/dL) LoD 2.2 mmol/L (0.101 g/L, 10.1 mg/dL) LoQ 2.2 mmol/L (0.101 g/L, 10.1 mg/dL)

Ethanol + NAD+ --ADH--> Acetaldehyde + NADH + H+

Enzymatic rate (kinetic) method using alcohol dehydrogenase (ADH); NADH formation is monitored photometrically as a rate of change in absorbance, directly proportional to ethanol concentration.

R1 — Buffer reagent: Buffer; preservatives (position B)
R3 — NAD/ADH reagent: NAD (yeast) ≥ 3 mmol/L; ADH (EC 1.1.1.1; yeast; 25°C) ≥ 617 μkat/L (37 U/mL); stabilizers; preservatives (position C)

Reaction procedure:

Sample (3.2 μL normal/increased, or 1.6 μL via the decreased sample volume function for high concentrations) is combined with R1 (buffer; preservatives), which establishes the reaction matrix/pH -- no color- or NADH-forming chemistry occurs at this step.
R3 (NAD+ and alcohol dehydrogenase, ADH) is added; ADH catalyzes oxidation of ethanol to acetaldehyde with stoichiometric reduction of NAD+ to NADH.
Because R3 supplies NAD+ and ADH in reagent excess relative to the very small sample volume, the rate of NADH accumulation is directly proportional to sample ethanol concentration; this rate is monitored bichromatically (700/340 nm) over the 10-minute reporting time and used to compute the result -- NADH formation, not ethanol itself, is the measured species.

Limiting reagent: Ethanol (sample analyte) is rate-limiting; NAD+ and ADH (R3) are supplied in reagent excess relative to the small sample volume (1.6-3.2 μL sample vs. 40 μL + 40 μL reagent) -- exact excess fold not stated.
Reaction notes:
R3 supplies NAD+ and ADH in reagent excess relative to the microliter-scale sample volume, so the initial rate of NADH formation (not an equilibrium endpoint) tracks ethanol concentration; NADH accumulation is what's optically monitored at 340 nm (700 nm reference), not ethanol itself.
Kinetics: Read as a rate (kinetic) reaction over a fixed 10-minute window rather than a true endpoint, with the rate of absorbance change proportional to ethanol concentration across the 2.2-108 mmol/L reportable range; calibration is linear (2-point, S1 water / S2 calibrator).
Readout: Bichromatic absorbance measurement (700/340 nm) tracking the rate of NADH generation; cobas c systems convert this rate to ethanol concentration (mmol/L, with g/L and mg/dL conversions available).
What's measured: Reagent is specific for ethanol. Measurable cross-reactivity was found with n-propanol (8.0% serum/9.9% urine) and n-butanol (2.8% serum/1.5% urine) at 2000 mg/dL; isopropanol, acetone, ethylene glycol, methanol, and acetaldehyde showed negligible (near-zero) cross-reactivity at the same concentration.
Interference implications: Icterus, hemolysis, lipemia, LDH/lactic acid, and common therapeutic-dose drugs show no significant interference in serum/plasma at the stated indices/thresholds; hemolysis, glucose, urea, creatinine, and drugs likewise show no significant interference in urine. Two cautions stand out: urine contaminated with microorganisms/sugars can ferment to produce a false-positive ethanol result, and rare IgM gammopathy (Waldenström's) may give unreliable results.
Known bias: Method comparison (Passing/Bablok and linear regression) of cobas c503, c303, and c703 results against the corresponding reagent on cobas c501 showed slopes of ~1.00-1.03 and r ≥ 0.998 across serum/plasma and urine, indicating no clinically significant bias between these platforms.

Interferences & pre-/post-analytical notes

Interferences

Known interferences

n-Propanol: Cross-reactivity: 8.0% (serum), 9.9% (urine) (Tested at 2000 mg/dL)
n-Butanol: Cross-reactivity: 2.8% (serum), 1.5% (urine) (Tested at 2000 mg/dL)

Suspected / theoretical

Gammopathy (IgM, e.g. Waldenström's macroglobulinemia): In very rare cases may cause unreliable results — Bakker AJ, Mücke M. Clin Chem Lab Med 2007;45(9):1240-1243.
Urine sugars with microbial contamination: May yield a false positive result due to fermentation of sugar to alcohol

Validated -- no significant interference

Icterus (conjugated bilirubin) - serum/plasma: No significant interference (I index up to 30 (approx. 513 μmol/L or 30 mg/dL conjugated bilirubin)) — Glick MR, Ryder KW, Jackson SA. Clin Chem 1986;32:470-475.
Icterus (unconjugated bilirubin) - serum/plasma: No significant interference (I index up to 60 (approx. 1026 μmol/L or 60 mg/dL unconjugated bilirubin)) — Glick MR, Ryder KW, Jackson SA. Clin Chem 1986;32:470-475.
Hemolysis - serum/plasma: No significant interference (H index up to 200 (approx. 124.2 μmol/L or 200 mg/dL hemoglobin)) — Glick MR, Ryder KW, Jackson SA. Clin Chem 1986;32:470-475.
Lipemia (Intralipid) - serum/plasma: No significant interference; poor correlation between L index and triglyceride concentration (L index up to 500) — Glick MR, Ryder KW, Jackson SA. Clin Chem 1986;32:470-475.
Drugs (common panels) - serum/plasma: No interference found at therapeutic concentrations — Breuer J. Eur J Clin Chem Clin Biochem 1996;34:385-386; Sonntag O, Scholer A. Ann Clin Biochem 2001;38:376-385.
LDH/lactic acid: No significant interference (tested via dose-response curve with purified LDH fractions added to 30 mmol/L lactic acid solution) (Up to 2000 U/L LDH)
Hemolysis - urine: No significant interference (H index up to 750 (approx. 466 μmol/L or 750 mg/dL hemoglobin))
Glucose - urine: No significant interference (Up to 111 mmol/L (2000 mg/dL))
Urea - urine: No significant interference (Up to 1800 mmol/L (10811 mg/dL))
Creatinine - urine: No significant interference (Up to 22.1 mmol/L (250 mg/dL))
Drugs (common panels) - urine: No interference found at therapeutic concentrations — Sonntag O, Scholer A. Ann Clin Biochem 2001;38:376-385.
Isopropanol: Cross-reactivity: 0.2% (serum), 0.5% (urine) -- negligible (Tested at 2000 mg/dL)
Acetone: Cross-reactivity: 0.0% (serum), 0.2% (urine) -- negligible (Tested at 2000 mg/dL)
Ethylene glycol: Cross-reactivity: 0.0% (serum), 0.2% (urine) -- negligible (Tested at 2000 mg/dL)
Methanol: Cross-reactivity: -0.1% (serum), 0.2% (urine) -- negligible (Tested at 2000 mg/dL)
Acetaldehyde: Cross-reactivity: -1.1% (serum), -0.3% (urine) -- negligible (Tested at 2000 mg/dL)

Pre-analytical

Do not use alcohol or other volatile disinfectants at the venipuncture site; aqueous Zephiran (benzalkonium chloride), aqueous Merthiolate (thimerosal), or povidone-iodine may be used instead.
Repeat assays must be performed on freshly poured cups due to evaporation of alcohol.
Ammonia/Ethanol/CO2 Calibrator cups must not be left open longer than 30 minutes at 15-25°C; Control cups must not be left open longer than 1 hour at 15-25°C.
Urine: use random urine, keep samples tightly closed, and centrifuge samples containing precipitates before performing the assay.
Do not use volatile solvents in the work area when performing assays; do not perform sample preparation (especially spiking of pools) in the immediate work area, since vapor contamination of reagents can impact calibration stability.
Do not use automatic rerun for high-concentration samples; use the decreased sample volume function (a 1:2 dilution, automatically multiplied by a factor of 2) on a fresh, tightly-closed aliquot instead.

Post-analytical

For diagnostic purposes, results should always be assessed in conjunction with the patient's medical history, clinical examination, and other findings.
Urinary:blood ethanol ratio is often reported as 1.3:1, but other lower or higher ratios may apply depending on patient population and factors such as urine volume produced and excreted.
The legal definition of intoxication varies by jurisdiction; each laboratory should establish an acceptable reporting format and procedures for reporting abnormal results.

Source: package insert (PDF, Cat #08057630190, rev V 4.0) · Extracted 2026-08-25 · Approved 2026-08-26

Siemens Atellica CH

kinetics endpoint λ 340 / 410 nm AMR 3.0–300.0 mg/dL (0.7–65.1 mmol/L) LoD 2.8 mg/dL (0.6 mmol/L) for serum and plasma; 3.0 mg/dL (0.7 mmol/L) for urine

Ethanol + NAD --ADH--> Acetaldehyde + NADH

Enzymatic endpoint assay (alcohol dehydrogenase method); the ADH-catalyzed oxidation of ethanol reduces NAD to NADH, producing a concomitant increase in absorbance proportional to ethanol concentration.

R1 — Reagent 1 (buffer): Tris buffer; surfactant; preservatives
R2 — Reagent 2 (enzyme/cofactor): MES, Tris buffer, preservatives, stabilizers; NAD (18 mmol/L); alcohol dehydrogenase (ADH, yeast) (> 525 kU/L)
Atellica CH Diluent:

Reaction procedure:

Sample pre-dilution: 50 μL of primary sample (serum, plasma, or urine) plus 200 μL Atellica CH Diluent are dispensed into a dilution cuvette (1:5 dilution) — brings the ethanol concentration into the working range of the enzymatic reaction before the small 8 μL aliquot is taken forward.
80 μL of R1 plus 2 μL special reagent water are dispensed into the reaction cuvette. R1 contains only Tris buffer, surfactant, and preservatives (no NAD or ADH), so this step establishes the pH/ionic reaction environment before any enzymatic chemistry begins — it does not itself generate signal or clear an interferent.
8 μL of the pre-diluted sample is dispensed into the reaction cuvette.
45 μL of R2 plus 2 μL special reagent water are dispensed into the reaction cuvette. R2 supplies the reactive components — ADH and NAD — that oxidize ethanol to acetaldehyde while reducing NAD to NADH; this is the analyte-specific, signal-generating step.
The mixture is mixed and incubated at 37°C to drive the ADH reaction to completion.
Absorbance is measured bichromatically (340/410 nm) after R2 addition — a single, fixed-time (endpoint) reading of NADH formation, not of ethanol directly.
The system calculates and reports the result from the measured absorbance change.

Limiting reagent: Ethanol (the analyte) is reagent-limiting: accounting for the 1:5 sample pre-dilution and reaction-cuvette volumes, NAD in R2 (18 mmol/L as supplied) works out to roughly 5.9 mmol/L in the final reaction mixture, versus only ~0.76 mmol/L ethanol at the top of the 300 mg/dL measuring range — an approximate 8-fold molar excess of NAD (and its co-supplied ADH) over substrate.
Reaction notes:
ADH and NAD are supplied together in R2 in large molar excess relative to the analyte: after accounting for the 1:5 sample pre-dilution and reaction-cuvette volumes, NAD works out to roughly 5.9 mmol/L in the final reaction mixture versus only ~0.76 mmol/L ethanol at the top of the 300 mg/dL measuring range (~8-fold excess), so ethanol is the reagent-limiting species and its concentration governs the extent of the reaction. R1, dispensed first, is only Tris buffer/surfactant/preservatives — it conditions the sample but does not react. The signal actually monitored is NADH formation (bichromatic absorbance at 340/410 nm), not ethanol itself; NADH is produced stoichiometrically with oxidized ethanol.
Kinetics: This is a fixed-time endpoint measurement: absorbance is read once after Reagent 2 addition and incubation at 37°C, not monitored as a continuous rate. This supports the linear reportable range of 3.0–300.0 mg/dL (0.7–65.1 mmol/L); results above this can be handled by the system's automatic-repeat function, which extends the effective reportable range to 900.0 mg/dL (195.3 mmol/L) and flags such results 'Autorepeat.'
Readout: Bichromatic absorbance is measured at 340/410 nm; the increase reflects NADH generated by ADH-catalyzed oxidation of ethanol, read as a single endpoint measurement after Reagent 2 addition and incubation.
What's measured: The assay is designed to quantify ethanol specifically via its oxidation by ADH. Because ADH also acts on other short-chain alcohols, the assay shows a specificity gap with n-propanol (26.9% cross-reactivity at only 30 mg/dL), while acetaldehyde, acetone, ethylene glycol, isopropanol, methanol, n-butanol, and propylene glycol showed <5% cross-reactivity at the higher concentrations tested. The method is traceable to a gas chromatography reference method via NIST materials and patient-sample correlation.
Interference implications: Hemolysis (up to 1000 mg/dL hemoglobin), conjugated/unconjugated bilirubin (up to 80 mg/dL), and lipemia (Intralipid up to 3000 mg/dL) all produced <10% bias, the insert's stated threshold for interference, and are validated non-interferents. A broad panel of drugs and endogenous substances tested in serum and urine likewise showed <10% bias at the concentrations tested. The one specificity flag is n-propanol: even at a low concentration (30 mg/dL) it shows 26.9% cross-reactivity, since it is also an ADH substrate and would read as falsely elevated ethanol if present.
Known bias: The assay is designed to correlate with Dimension RxL ETOH at r > 0.960 and slope 1.0 ± 0.1; observed results were serum y = 1.05x + 1.5 mg/dL (r = 0.995, N = 140) and urine y = 1.05x − 0.8 mg/dL (r = 0.998, N = 103), indicating a small (~5%) proportional positive bias versus the Dimension RxL comparator.

Interferences & pre-/post-analytical notes

Interferences

Known interferences

n-Propanol: 26.9% cross-reactivity — meaningfully inflates apparent ethanol result even at a low concentration (30 mg/dL (5.0 mmol/L))

Validated -- no significant interference

Hemoglobin (hemolysis): 6% bias at 50.4 mg/dL ethanol, -1% bias at 101.0 mg/dL ethanol (threshold for interference is >10% bias) (1000 mg/dL (0.624 mmol/L))
Bilirubin, conjugated: 3% bias at 56.1 mg/dL ethanol, 4% bias at 106.0 mg/dL ethanol (80 mg/dL (1368 μmol/L))
Bilirubin, unconjugated: 0% bias at both tested ethanol concentrations (80 mg/dL (1368 μmol/L))
Lipemia (Intralipid): 1% bias at both tested ethanol concentrations (3000 mg/dL (33.9 mmol/L))
Acetaldehyde: -1.0% cross-reactivity (1000 mg/dL (227 mmol/L))
Acetone: 0.0% cross-reactivity (2000 mg/dL (344 mmol/L))
n-Butanol: 4.2% cross-reactivity (250 mg/dL (33.8 mmol/L))
Ethylene glycol: 0.2% cross-reactivity (2000 mg/dL (322 mmol/L))
Isopropanol: 0.4% cross-reactivity (2000 mg/dL (333 mmol/L))
Methanol: -0.1% cross-reactivity (2000 mg/dL (624 mmol/L))
Propylene glycol: 0.0% cross-reactivity (2000 mg/dL (263 mmol/L))
Acetaminophen (serum): < 10% bias (20.0 mg/dL (1324 μmol/L))
Amikacin (serum): < 10% bias (8.0 mg/dL (137 μmol/L))
Ampicillin (serum): < 10% bias (5.3 mg/dL (152 μmol/L))
Ascorbic acid (serum): < 10% bias (6.0 mg/dL (342 μmol/L))
Caffeine (serum): < 10% bias (6.0 mg/dL (308 μmol/L))
Carbamazepine (serum): < 10% bias (3.0 mg/dL (127 μmol/L))
Chloramphenicol (serum): < 10% bias (5.0 mg/dL (155 μmol/L))
Chlordiazepoxide (serum): < 10% bias (1.0 mg/dL (33.3 μmol/L))
Chlorpromazine (serum): < 10% bias (0.2 mg/dL (6.27 μmol/L))
Cholesterol (serum): < 10% bias (503 mg/dL (13 μmol/L))
Cimetidine (serum): < 10% bias (2.0 mg/dL (79.2 μmol/L))
Creatinine (serum): < 10% bias (30.0 mg/dL (2.7 mmol/L))
Dextran 40 (serum): < 10% bias (6000 mg/dL (1500 μmol/L))
Diazepam (serum): < 10% bias (0.51 mg/dL (18.0 μmol/L))
Digoxin (serum): < 10% bias (6.1 ng/mL (7.8 nmol/L))
Erythromycin (serum): < 10% bias (6.0 mg/dL (81.6 μmol/L))
Ethosuximide (serum): < 10% bias (25.0 mg/dL (1770 μmol/L))
Furosemide (serum): < 10% bias (6.0 mg/dL (181 μmol/L))
Gentamicin (serum): < 10% bias (1.0 mg/dL (21 μmol/L))
Heparin (serum): < 10% bias (3.0 U/mL (3000 U/L))
Ibuprofen (serum): < 10% bias (50 mg/dL (2427 μmol/L))
Immunoglobulin G (IgG) (serum): < 10% bias (5.0 g/dL (50 g/L))
Lactate (serum): < 10% bias (901 mg/dL (100 mmol/L))
Lactate dehydrogenase (serum): < 10% bias (237,500 U/L)
Lidocaine (serum): < 10% bias (1.2 mg/dL (51.2 μmol/L))
Lithium (serum): < 10% bias (2.2 mg/dL (3.2 mmol/L))
Mannitol (serum): < 10% bias (500 mg/dL (27.4 mmol/L))
Nicotine (serum): < 10% bias (0.10 mg/dL (6.2 μmol/L))
Penicillin G (serum): < 10% bias (25 U/mL (25000 U/L))
Pentobarbital (serum): < 10% bias (8.0 mg/dL (354 μmol/L))
Phenobarbital (serum): < 10% bias (10.0 mg/dL (431 μmol/L))
Phenytoin (serum): < 10% bias (5.0 mg/dL (198 μmol/L))
Primidone (serum): < 10% bias (4.0 mg/dL (183 μmol/L))
Propoxyphene (serum): < 10% bias (0.16 mg/dL (4.91 μmol/L))
Protein (Albumin) (serum): < 10% bias (6.0 g/dL (60 g/L))
Protein (Total) (serum): < 10% bias (12.0 g/dL (120 g/L))
Salicylic acid (serum): < 10% bias (60 mg/dL (4.34 mmol/L))
Theophylline (serum): < 10% bias (4.0 mg/dL (222 μmol/L))
Triglycerides (serum): < 10% bias (3000 mg/dL (33.9 mmol/L))
Urea (serum): < 10% bias (500 mg/dL (83 mmol/L))
Uric acid (serum): < 10% bias (20 mg/dL (1.2 mmol/L))
Valproic acid (serum): < 10% bias (50 mg/dL (3467 μmol/L))
Acetone (urine): < 10% bias (1.0 g/dL (1.72 mol/L))
Ascorbic acid (urine): < 10% bias (1.5 g/dL (45.4 μmol/L))
Bilirubin (urine): < 10% bias (2.0 mg/dL (34.2 μmol/L))
Creatinine (urine): < 10% bias (0.5 g/dL (440 mmol/L))
Gamma globulin (urine): < 10% bias (0.5 g/dL (5.0 g/L))
Glucose (urine): < 10% bias (2 g/dL (0.11 mol/L))
Hemoglobin (urine): < 10% bias (115 mg/dL (1.15 g/L))
Human serum albumin (urine): < 10% bias (0.5 g/dL (5.0 g/L))
Oxalic acid (urine): < 10% bias (0.1 g/dL (110 mmol/L))
Riboflavin (urine): < 10% bias (7.5 mg/dL (2.0 mmol/L))
Sodium chloride (urine): < 10% bias (6.0 g/dL (10.3 mol/L))
Urea (urine): < 10% bias (6.0 g/dL (10.0 mol/L))
Boric acid (urine): < 10% bias (1% w/v (162 mmol/L))
Sodium azide (urine): < 10% bias (1% w/v (154 mmol/L))
Sodium fluoride (urine): < 10% bias (1% w/v (238 mmol/L))

Pre-analytical

Due to the volatile nature of alcohol, specimen tubes should be completely filled and capped to avoid evaporative loss; samples should be opened and processed in STAT mode.
Use non-alcohol germicidal solution to cleanse the venipuncture site; reusable collection containers, syringes, and needles must not be cleaned or stored with alcohol or other volatile solvents.
Urine specimens within pH 3.0–11.0 do not require prior pH adjustment.
Specimens may be stored up to 2 days at room temperature; serum up to 2 weeks at 2–8°C or indefinitely frozen at ≤-20°C; urine at 4°C until analysis or indefinitely frozen at ≤-20°C.
Samples must be free of bubbles/foam and fibrin or other particulate matter before analysis; centrifuge to remove particulates per CLSI guidance.

Post-analytical

The system flags all results outside the 3.0–300.0 mg/dL (0.7–65.1 mmol/L) measuring interval; an optional automatic-repeat feature extends the effective reportable range to 900.0 mg/dL (195.3 mmol/L) for serum, plasma, and urine, flagging such results 'Autorepeat.'
Conversion formula: mg/dL × 0.217 = mmol/L.
Results should always be interpreted in conjunction with the patient's medical history and clinical presentation; the fatal blood alcohol concentration has been reported as >400.0 mg/dL (86.8 mmol/L).

Source: package insert (PDF, Cat #11097501, rev Rev. 05, 2024-11) · Extracted 2026-08-25 · Approved 2026-08-26

Comparison highlights

Both platforms use the same ADH chemistry but differ in kinetics: Roche Cobas c503 runs a kinetic (rate) method reading NADH accumulation over a 10-minute window, while Siemens Atellica CH uses a fixed-time endpoint reading after incubation to completion — a rate artifact (e.g., a slow side reaction) could bias the Roche result differently than it would the Siemens endpoint.

n-Propanol cross-reactivity is far more pronounced on Siemens: Atellica CH shows 26.9% cross-reactivity at just 30 mg/dL n-propanol, versus Roche's 8.0% (serum) at a much higher tested concentration (2000 mg/dL) — a patient with co-ingested n-propanol could show a much larger false elevation on Siemens than on Roche.

n-Butanol cross-reactivity also differs: Siemens reports 4.2% at 250 mg/dL, while Roche reports a lower 2.8% (serum) at a much higher 2000 mg/dL, suggesting Siemens' assay is comparatively more butanol-sensitive per unit concentration.

Analytical ranges and sensitivity are not identical: Roche's AMR is 10.1–498 mg/dL with LoD/LoQ both at 10.1 mg/dL, while Siemens spans a wider 3.0–300.0 mg/dL with a lower LoD (~2.8–3.0 mg/dL) — Siemens can detect and quantify lower-level ethanol that would fall below Roche's reporting floor, while Roche's upper limit extends further before requiring dilution.

Lactate/LDH interference was assessed differently and both cleared it: Roche explicitly dosed purified LDH up to 2000 U/L into a 30 mmol/L lactate solution and found no significant interference; Siemens tested LDH up to 237,500 U/L (and lactate up to 901 mg/dL) with <10% bias — reassuring given the overview's warning that LDH-driven lactate-to-pyruvate NADH generation can mimic ethanol signal, though Siemens' much higher LDH ceiling gives a wider validated margin.

Sample handling differs: Roche uses a very small direct sample volume (3.2 μL, or 1.6 μL via a reduced-volume mode for high concentrations) with reagent supplied in large excess, whereas Siemens performs an explicit 1:5 pre-dilution step before drawing an 8 μL aliquot forward — a difference relevant to pipetting/dilution error propagation, though not itself a chemistry difference.

Each platform's bias claim is anchored to a different comparator: Roche's cross-platform agreement (slopes ~1.00–1.03, r≥0.998) is versus its own cobas c501 reagent, while Siemens' regression (~5% proportional positive bias, r>0.99) is versus Dimension RxL ETOH — neither claim demonstrates agreement with the other platform directly, so a formal method comparison between Roche and Siemens results would still be advisable before treating them as interchangeable.

Interferent panels tested are asymmetric in scope: Siemens validated a very broad panel of >50 named drugs and endogenous substances (serum and urine) at <10% bias, while Roche's insert emphasizes icterus/hemolysis/lipemia indices and urine solutes plus two qualitative cautions (urine fermentation by contaminating sugars, and rare IgM gammopathy) not mentioned in the Siemens data provided — the absence of a finding on one insert doesn't confirm the other platform is unaffected.

Generated 2026-08-26 · Approved 2026-08-26

Lab comparison

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