Dilute Samples - What is a dilute? Should I be concerned?

Submitted on Jan 13, 2015

Most reports of a negative-dilute specimen are nothing to be concerned with, however some situations can be a red flag and require further testing. The main thing to note is that a negative-dilute specimen is NOT the same as a positive result. A dilute specimen is just that....a dilute specimen. Dilute specimens that are positive are not reported as positive-dilute they are reported as a positive. The dilute status is not of concern. Whenever receiving a dilute specimen report, it is important to have an MRO involved in the review process, even if the test is a Non-DOT.  The MRO will be able to review and determine specific situations of concern, such as excessively low levels of creatinine that would require a re-test under direct observation. Employers should also have a clear policy on dilute specimens and protocols on what they will do, such as re-testing or when a direct observation should be required. The best Non-DOT employer polices mirror the Federal Requirements and would require re-testing or observations under the same circumstances that a DOT covered test would. 

What is a Dilute?
Dilution is the process of reducing the concentration of drug or drug metabolites in the sample. This is accomplished by adding fluid to the sample or by drinking large amounts of fluid to dilute the specimen, called "internal dilution." If the amount of the natural substance creatinine in the urine is abnormally low, internal dilution may be the cause. A dilute specimen can be caused by several circumstances. There are some medical conditions that produce dilute urine as well.
Should I be Concerned?
It is recommended that an Employer have a section in their Drug Testing Policy that another specimen be collected as soon as possible with minimum advance notice. This will help create safeguards against anyone that may have tried to dilute a sample on purpose or that may have tried to tamper with a specimen. However, the employer may also elect to accept the negative results with the notation “dilute” from the lab. Please note a dilute is not a positive test and under most circumstances there is a valid reason for a specimen being diluted, however we feel it is always better to re-test. Our MRO always recommends a re-test to rule out any other possibilities. 
Employers may require the donor to submit another specimen collection. The re-collection cannot be done under direct observation, unless directed by the MRO. If the second test is negative-dilute, the employer must accept that result and cannot continue re-collections. Under specific conditions a direct observation is required for a dilute specimen. The MRO will instruct the employer to re-test the donor with no notice and that the specimen must be observed. The MRO will be clear when a direct observation is required. An applicant / employee’s refusal to submit to a re-collection for negative-dilute results is a refusal to test under DOT rule.