Side-by-side cutoff comparison
At 100 ng/mL, a laboratory reports lower EtG concentrations that would be negative at 500 ng/mL. Research in outpatient populations found that lower cutoffs were more useful for detecting drinking across multiple days, while 500 ng/mL primarily identified more recent or heavier exposure.
Sensitivity and specificity tradeoff
Sensitivity is the ability to detect exposure when it occurred. Specificity is the ability to remain negative when it did not. Lowering the cutoff usually raises sensitivity and may lower specificity; raising it does the reverse.
Which EtG cutoff does my test use?
Policies differ. Clinical programs, courts, employers, treatment providers, and home tests may not use the same threshold. Ask the laboratory or ordering organization rather than guessing from a brand name or detection-time claim.
How to interpret a near-cutoff result
A number near a cutoff deserves context. Confirmation method, creatinine, collection timing, known alcohol-containing products, and EtS may all be relevant. A single concentration should not be reverse-calculated into an exact drinking history.
Evidence and limitations
This guide summarizes primary research and public-health guidance. Group-level findings cannot predict one person's result.