What Does a “Dilute” Drug Test Result Mean? - American Society of Employers - Susan Chance

What Does a “Dilute” Drug Test Result Mean?

Some drug test results return as “dilute.” While a result of “positive dilute” is a positive result, a test that shows “negative dilute” does not necessarily mean the test is negative.drugs

Over-hydrating before a drug screen can cause a negative dilute result. This result can also be caused by the subject trying to cheat the test.

Cut-off levels for each type of drug being tested are used, so a result will only show as positive if the drug is above a specific level. For example, a subject who has a cold and has been prescribed cough medicine with codeine in it can fail the test if the level in their system is above the cut-off level. This could point to abusing the medication.

Cut-off levels also help to prevent false positive results. It is very rare, but in some cases, eating poppy seeds before a urine drug screen can cause the test to show opium in the specimen. Eating foods with other substances such as hemp, in legal amounts, could also show up in the specimen. Ephedrine, a decongestant, can also cause a false positive for amphetamines.

Other methods to assist in ensuring testing accuracy include measuring the pH level, creatinine level, and specific gravity of the sample. The pH level is the measure of acid-base in the urine and the normal range is from 4.5 to 9. Creatinine is a product of our kidneys and is a normal part of urine and the concentration should be at 20 mg/dL. Specific gravity in urine testing measures the concentration of dissolved particles in the urine. The normal range is an approximation of 1.0020 to 1.0200.

These checks help to identify if any adulterants were used to try to cheat the test by providing a sample that is not normal for a human specimen. One of the most common ways to try to cheat a test is to ad an adulterant to the sample. Everyday household items such as vinegar, bleach, ammonia, and beverages such as lemonade and soft drinks are used to try to alter or substitute the specimen.

Most employers will send the subject for a second test if the initial result is negative dilute. Best practice for a second test is to require the subject to go for the collection within 24 hours or less of being notified of the requirement for a second test. For Department of Transportation (DOT) testing they will allow a second test.  A second result of negative dilute is considered a negative result, and you may not send the person for additional tests. For non-DOT testing it is up to the employer on how they want to handle the situation. Typically, a second negative dilute would be accepted as a negative result as it is with DOT testing.

If you are an employer who has a drug testing policy, make sure that you have a clear policy on negative dilute results, and that you treat everyone the same under the policy.

Additional ASE Resources
ASE Drug Screening - ASE can accommodate all of your drug screening needs, including: pre-employment, random,  reasonable suspicion, and post-incident testing. For more information contact Susan Chance.

ASE Handbook Development- If you would like your current drug testing policy reviewed, revised, or a new policy created ASE can help.  Contact Mike Burns.


 

Sources:  Medicalnewstoday.com, questdiagnostics.com, drugs.com, transportation.gov, workingpartners.com, indeed.com

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