What Could Cause A False Positive In An Alcohol Test?

Posted on Tue, 30 Jun 2015

Question: I took an Alco brand mouth swab test tonight for alcohol and it came back positive for alcohol. I do not understand why because I have not drank at all since 12 AM Sunday and it was about 6:15 PM today (Tuesday) when this test was administered. The only things I had eaten today before the test had been Reese's Cups and pizza from Papa John's, and I drank 24 oz. of coffee this morning and a few 12 oz. cans of Mt. Dew throughout the day, along with some water. I also had taken a drink from a Gatorade not long before the test was administered, and I'm not sure that the full 15 minutes had passed before taking the test. I currently take Keppra XR 1500 mg daily and just recently started taking 60 mg Dexilant this morning. I am 5'8" 152 pounds and a male. One thing I'd like to note is that I work at a junk yard and had been exposed to A LOT of beer cans around 4:30 PM when I was emptying them into tubs to be put up for the end of my work day at 5. Is it possible that being exposed to the alcohol in these cans produced a positive result? Any information would be greatly appreciated as I am extremely confused as to why it would say I have a BAC when there is just no possible way that I would. Thank you.

Answered by Dr. Dr. Matt Wachsman (1 hour later)

Brief Answer:
several ways there can be

Detailed Answer:
false readings.Other sources of alcohol. Various foods, mouth washes, shaving aids, and hand sanitizer if a lot of it is inhaled. If I worked in a junk yard I would have a lot of hand sanitizer around. The beer cans are not very likely at all since the amount of alcohol in beer is low. the amount in hand sanitizer is high.

With a very large amount of alcohol on sunday, 48 hr later... depends on the particular test characterisitics. some alcohol urine tests are definitely set up to detect alcohol in the system that far into the past.

Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar

Follow up: Dr. Dr. Matt Wachsman (17 minutes later)

Well I know that I didn't use mouth wash, any kind of shave aid, or hand sanitizer (I don't think anyway, there is a soap that has some kind of grainy substance in it that I wish my hands with on a regular basis at work, I have no idea if it has any kind of hand sanitizer like substance in it though). Keep in mind this was not a urine test at all. It was simply a thin stick with a small pad on the end used inside the mouth, and the pad end is placed into a vial to sit in a small amount of the test subjects saliva It has very specific things about it. One is that nothing is supposed to be placed into the mouth in terms of food, drink, tobacco product, etc. for 15 minutes before the test, and as I said, I had drank some Gatorade not long before taking the test, and I'm not sure if it had been a full 15 minutes that had passed before taking the test. It also says that after 2 minutes 30 seconds the test results can be "erroneous" and I know for a fact that it was much longer than 2 minutes 30 seconds before the results were read. It just blows my mind how it could possibly be saying that I have a current BAC when it is simply a mouth swab test meant to detect current alcohol levels and I know that I had not drank in basically 66 hours and I would say after at least the first 12 of those 66 hours my BAC should have tested at 0.00. I'm very familiar with ETG testing and how it can trace metabolites of alcohol in urine, and I've taken a few and passed all of them under similar circumstances, but this again as I said is NOT a urine test by any means. ETG has to be sent to a lab and tested much more thoroughly than this where results are gotten in a very short amount of time.

Answered by Dr. Dr. Matt Wachsman (7 hours later)

Brief Answer:
if it's much longer than 2 minutes then that's it.

Detailed Answer:
the test works on an oxidation reaction with alcohol probably. Most of the strips work with an enzyme that oxidizes a XXXXXXX and a second enzyme that makes a chemical to run that one in the presence of the particular target (urine test strips for glucose, etc). The XXXXXXX can directly oxidize over time/temperature.

and I think I mentioned motor fuel can show up as positive
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC0000/
the alco swab is mentioned as reacting with drugs (prescription not abuse) but the sources do not give which drugs and how they know this.
OH, and it's a color test. the color of the gatorade will directly change the test.
ETG has it's own false positives but not false negatives. It is a Period rather than a point time test.... it measures heavy alcohol use over the last several days, so, it's considerably more sensitive than a swab or breathalyzer.

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Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar