Substance Abuse Screening and Negative Dilute Results
Substance Abuse Screening and Negative Dilute Results
PLEASE NOTE: The following is presented as general educational information. It is not legal advice, either express or implied. Consultation with your legal counsel is recommended for all employment law matters.
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The workplace testing of urine for drugs of abuse is a common practice which had its beginnings in Executive Order 12564 issued by the White House in September of 1986. In the past 20 years, the testing program has matured and evolved both in scope and in scientific and technical aspects.
Today testing methods are capable of finding drugs of abuse that are present in concentrations measured in parts per billion. Testing is done at precisely established cutoff levels, and if a drug is present in a concentration that is 1 part per billion below the established cutoff, the sample is reported as negative. These cutoffs were originally established after exhaustive research to avoid any possibility of reporting false positives. This was done so that the possibility of accusing someone of using an illicit drug when in fact that person had not done so was minimized as much as possible.
Since the difference between a positive and a negative report may hinge on a drug concentration of only 1 part per billion, those involved in workplace drug testing should be aware of conditions that may cause drug concentration to fluctuate and possibly produce a result that does not accurately indicate the presence or absence of an illicit drug. As drug free workplace programs have evolved, a parallel industry devoted to finding any and all means of hiding the presence of illicit drugs has evolved right along with it. A Google search for the term "beat a drug test" will produce millions of hits, the vast majority being links to entrepreneurs selling methods to alter urine specimens in the hope of beating a drug test. One of the most common ways to do this is to drop the concentration of drug in the specimen to below the established drug cutoff. If that drug concentration can be made to decrease by as little as 1 part per billion, a person using illicit drugs may have found a way to pass the drug test. The dilution of a urine specimen may be one of the easiest ways to pass a drug test.
Unfortunately, not all dilute urine specimens are evidence of drug users trying to cheat the test. There are many reasons for urine specimens to be dilute, including disease states, medical advice, habits of fluid consumption, and types of fluid consumed by normal people living normal lives. Those in the testing industry must choose the definition of "normal urine" that they are going to accept. In other words, they must choose a range of values that define a specimen that is "consistent with normal human urine" and decide upon the actions that will be taken when a urine specimen is found to be outside that range. That plan of action must take into account the fact that urine may be only a little abnormal, or may be way out of the accepted range.
Dilute Urine Specimen Definition
It's important to understand exactly what a dilute urine specimen is, and more importantly, what it isn't. The testing of urine specimens to establish that the specimen is consistent with normal human urine is called "Specimen Validity Testing" (SVT). Please note that the testing does not guarantee that the specimen is human urine, only that it is consistent with normal human urine.
All human urine contains a protein called creatinine. This protein comes from the normal physiologic breakdown of muscle tissue and is always present. If a specimen has no creatinine in it, it isn't urine. Conversely, if a specimen does have creatinine in it, then at least a portion of that specimen is urine, but there is no guarantee that the entire specimen is urine.
There are two other measurements taken as a part of SVT to help establish the normalcy of the specimen being tested. These are Specific Gravity and pH, the latter of which is a measure of the acid/base balance of a substance. Together, the measurements of creatinine concentration, specific gravity, and pH determine that the specimen contains urine, and if the measured results are within certain defined ranges then the specimen is most probably human in origin.
The range of values considered normal for human urine is a wide one, and the range of values outside the normal range is wide as well. To be considered "normal" the creatinine concentration must be between 20 mg/dl and 250 mg/dl, and the Specific Gravity must be between 1.0030 and 1.0200 (water has a Specific Gravity of 1.0000). pH must be between 4.5 and 9. A pH of 7 is considered neutral, the substance having equal concentrations of acid and base, the lower the pH the more acid, the higher the more basic the substance.
Urine specimens having values inside these ranges are considered normal; those specimens with values falling outside of these ranges are not, but that does not necessarily mean that out of range specimens produce invalid drug test results. Specimens having values outside these ranges, while not "normal", are not necessarily considered "not consistent with normal human urine". Sometimes they are variants of normal, and where creatinine and Specific Gravity are concerned, these specimens may fall into a great big gray area called "Dilute". The purpose of this document is to provide information so employers can make informed decisions about what, if anything, needs to be done when presented with a report that says the tested urine specimen was "Dilute".
Dilute Specimen Reports
The biggest problem facing employers is what to do about drug test results that are reported as "Negative, dilute". If a specimen is "Positive" for a drug or metabolite, and is also dilute, the specimen is still positive for the drug, and the donor will fail the drug test. The notation that the specimen was dilute may be interesting, but it is not relevant to the handling of the positive test result.
This is not true for "Negative, dilute". In the paragraphs above, we defined the range of normal. We may also define ranges of abnormal and degrees of abnormality. The concentration of creatinine in a specimen theoretically may vary from 0 to immeasurably high, and it is necessary to be able to differentiate what is unquestionably not normal human urine (a "Substituted" specimen) from what is arguably only a variant of normal. Then a second decision must be made about what to do with a negative result from a specimen that may be only a variant of normal, but may still not represent an accurate test for the presence of illicit drugs. Remember, a difference of as little as 1 part per billion of drug is all it may take to turn a positive drug test into a negative one.
In urine Specimen Validity Testing (SVT) creatinine and pH are always measured. Since pH is not relevant to urine dilution, it will receive no more attention here. If the creatinine is below 20 mg/dl, Specific Gravity is also measured. If the measured creatinine is less than 20 mg/dl and the measured Specific Gravity is less than 1.0030, the urine specimen is considered to be dilute. Going farther down this dilute continuum, if the measured creatinine is less than 2 mg/dl and the Specific Gravity is less than 1.0010 (or greater than 1.0200) the specimen is considered to be not consistent with normal human urine and is reported as a "Substituted Specimen". On medical review, donors who have submitted such a specimen are asked to show how they could physiologically do that, and when they are unable to do so, the drug test result is officially a "Refusal to Test because of a Substituted Specimen". According to the Federal Department of Transportation (DOT) rules and the Federal Department of Health and Human Services (HHS) guidelines, if the Medical Review Officer (MRO) believes the donor has even a small possibility of being able to demonstrate that he or she has the ability to physiologically produce this type of specimen, up to 5 days may be allowed for the donor to do so.
This protocol is necessary because the values listed were not always the values associated with specimen substitution. When the SVT standards were originally disseminated by HHS in 1998 the creatinine value of 5 mg/dl was considered to be not consistent with normal human urine. A tremendous controversy ensued when, in 2001, a scientifically controlled study was performed on a flight attendant that proved she could physiologically produce normal urines with a creatinine value of less than 5 mg/dl. Hence in 2003, DOT lowered its creatinine reporting threshold and HHS followed suit in 2004 making less than 2 mg/dl creatinine and a Specific Gravity of less than 1.0010 (or greater than 1.0200) the new reporting threshold for Substituted Specimens.
Negative-Dilute Result; DOT and HHS
HHS issued Mandatory Guidelines for SVT in November, 2004. DOT continues to authorize but not require SVT, but does require that if SVT is done the testing must conform to the HHS Guidelines. In May of 2003, DOT issued an Interim Final Rule (IFR) which specified how MROs were required to handle certain DOT dilute specimens. Additionally, in December of 2005 DOT issued a proposed rule (NPRM) that, among other things, will make SVT mandatory when the final rule is issued. This final rule was expected by the end of 2006, but is still pending. There is general agreement between the DOT rules, the IFR, and HHS guidelines for dealing with substituted specimens, but these agencies differ in the manner in which they deal with certain negative dilute results.
To completely understand why these two respected agencies differ, and to decide as an employer what may be the best policy to adapt for non-regulated testing, it is necessary to break up the group of dilute specimens (creatinines of 2 mg/dl to less than 20 mg/dl) into two categories. For simplicity we will call them "dilute" and "hyper-dilute" and define them as follows:
- HYPER-DILUTE: Specimens with creatinines of greater than or equal to 2 mg/dl but less than 5 mg/dl; Specific Gravity less than or equal to 1.0010
- DILUTE: Specimens with creatinines of 5 mg/dl or greater but less than 20 mg/dl and Specific Gravity greater than 1.0010 but less than 1.0030.
Regarding these two categories of dilute, DOT and HHS differ as follows:
- DOT requires in the IFR that an immediate re-collection be done under direct observation when the specimen is found to be a hyper-dilute negative. Medical Review Officers (MROs) do not interview these donors, but report the result as a "Negative, dilute, Immediate Observed Re-collection Required".
- HHS guidelines do not differentiate hyper-dilute and dilute specimens from each other in any way. HHS looks at specimens with creatinines of 2 mg/dl or greater but less than 20 mg/dl to be simply dilute, and HHS does not specify or recommend any action to be taken by employers in those cases.
What should an employer do?
Clearly, if an employer is covered by DOT, DOT rules prevail. Unfortunately, DOT rules are only specific on required employer actions for hyper-dilute specimens. Employer actions for other dilute negatives are left to the policy of the employer, with certain DOT stipulations. The picture is less clear when non regulated populations are involved, and it is helpful in the decision-making process to understand the thinking behind the DOT re-collection requirement.
Even though a flight attendant demonstrated that she could physiologically produce urine with a creatinine value of less than 5 mg/dl, there have been very few similar demonstrations and current thinking is that the vast majority of the population taking drug tests does not do so. Therefore, hyper-dilute urine specimens may deserve a higher level of scrutiny. Anecdotal evidence supports this thinking: In 2003 a population of donors who produced hyper-dilute specimens had their urine re-collected. The re-collected urines showed a drug positivity rate of 17.8% in a population where the expected positivity rate is between 3-4%.
Data is less convincing for specimens that are simply dilute. DOT rules (49 CFR Part 40.197) allow the employer to make a decision to re-collect these donors one time under the following circumstances:
- There is a policy statement in place before the fact that allows the practice.
- All employees are treated equally.
- The re-collections are not observed re-collections.
- Only one re-collection is allowed, and the result of the second collection is the result of record, even if it is another negative, dilute.
- The decision to re-collect may vary by reason for test. In other words, an employer may decide to re-collect all pre-employment dilute negatives, but not random dilutes, or vice versa.
Unfortunately, there is little data that can be used on which to base a policy decision. An HHS study from the early 1990s that is no longer available reported only a minor increase in drug positivity rates if a dilute urine specimen was concentrated and tested at Federal cutoffs. This may be explained in part because there is no unique level that is considered "normal" that can be used when a dilute urine specimen is artificially concentrated attempting to make it more "normal". The range of normal is large (20-250), as has already been indicated.
Deciding how to treat negative dilute urines is up to the employer. The employer's decision should be based upon a number of factors, including:
- The demographics of the group of people being tested (high risk, low risk employees);
- Concerns for safety relative to the tested group;
- Whether or not there is a mix of regulated and non-regulated employees and a need or wish to treat both groups alike;
- The philosophical position of the employer.
It is not an easy decision, and over time data from the collection and the results of re-collections will need to be evaluated to determine a proper course of action.