What is a Dilute Specimen?
It’s not uncommon for employers to receive reports of drug screen results with the term “dilute specimen” associated with either a negative or positive result. In my former position as a Clinic Manager our Medical Review Officer (MRO) office would receive several phone calls a week asking us to explain what a dilute specimen result meant and what actions the Designated Employer Representative (DER) was required to take in order to maintain compliance with DOT regulations. Federal drug testing regulations outline the roles and responsibilities of laboratories, MROs and employers for handling a dilute specimen. However, some of the terminology used in each of these functions may be a little confusing. Let’s see if we can simplify things.
Laboratory Responsibilities
Labs must determine the creatinine levels of every specimen being tested. What is creatinine? Creatinine is a byproduct of creatine phosphate caused by muscle contractions and is filtered out of the blood through the kidneys. Normal creatinine levels indicate the test sample is undiluted, whereas low amounts of creatinine in the urine indicate the specimen has either been adulterated or manipulated in some way.
Labs use creatinine levels as a trigger to conduct further validity testing. If the creatinine level is less than 20 mg/dL, then the labs will also determine the specific gravity (the ratio of urine to water), as well as pH levels. They will also test for the presence of oxidants (bleach or ammonia) in the urine. These procedures are part of the validity testing.
Let’s look at the creatinine and specific gravity levels and how they relate to the specimen result. Labs report specimens as “dilute” when the creatinine levels are equal to or greater than 2 mg/dL and less than 20 mg/dL, and the specific gravity levels are greater than 1.0010 but less than 1.0030 (the specific gravity level of water is 1.0000). I know this may be pretty technical, but that is the criteria for reporting “dilute” results. Scientists have established that the urine of normally hydrated person will not have creatine and specific gravity levels in this range.
If drug testing results are reported as “positive dilute specimen” – that is, the specimen tests positive for drugs and is also dilute – the results are considered positive. The fact that the specimen is dilute is irrelevant. If results are reported as “negative dilute specimen” the results are considered negative. However, there may be additional requirements for negative dilute specimens. These requirements may fall upon the MRO and/or the DER.
MRO Responsibilities
Upon receiving a negative dilute specimen result, the MRO must consider creatinine and specific gravity levels, which ultimately determines actions taken.
If the creatinine level is equal to or greater than 2 mg/dL but less than 5 mg/dL and the specific gravity level is greater than 1.0010 but less than 1.0030, then the DOT mandates the MRO to instruct the DER to have the specimen immediately recollected under direct observation. In other words, the specimen is valid but DOT requires another collection due to the rarity of the labs findings (40.197 (b)1)). In the MRO world, these results are labeled “Extreme Dilutes”.
If the MRO receives a negative dilute specimen result with creatinine levels equal to or greater than 5 mg/dL but less than 20 mg/dL, then the result is reported as a negative dilute and neither the MRO nor the DER are required to perform any other actions, unless outlined in the employer’s drug and alcohol testing policy.
DER Responsibilities
If the DER is instructed by the MRO to have a specimen immediately recollected under direct observation, then the DER must comply with the MRO’s instructions and federal guidelines. For negative dilute results that do not require an immediate recollection, the MRO may note “Negative dilute, defer to company policy” on the results. Some companies conduct a recollection based on any result reported as a negative dilute specimen. The process of handling all dilute specimens should be outlined in the employer’s drug and alcohol testing policy.
I have talked to DERs that consider any dilute specimen result as a positive result or an attempt by the applicant to “beat the test”. I don’t agree. I realize there are people who try to beat drug tests. But not everyone is out to beat the system. Subjects who have previously tested understand they need to be able to provide a specimen when directed and will therefore drink plenty of fluids in advance. On the other hand, there are individuals who will try to “flush” their system with water in order to provide a “clean” specimen. Finally, there are those individuals that produce low creatinine levels naturally.
Regardless of how labs test or MRO’s report results or the causes of a dilute specimen, a company must be knowledgeable of these situations and have a plan of response. It is a best practice for companies to have recollection procedures for negative dilute specimens outlined in their drug and alcohol testing policy. Take note: These recollections may not be conducted under direct observation. Only extreme dilute specimens require recollection under direct observation. If it’s not a DOT test, companies may consider recollections using alternative testing methods for negative dilute results, such as hair or saliva testing.