Specimen Validity Testing

As mentioned earlier, the federal urine drug-testing regulations contain provisions for MROs to review and evaluate drug test results where the test result is reported by the laboratory as adulterated, substituted or invalid. The MRO conducts an interview with the specimen donor as with a confirmed positive test result and makes a final test result determination for reporting to the employer.

Specimen validity testing SVT is defined as the evaluation of a specimen to determine if it is consistent with normal human urine. SAMHSA has defined the requirements that laboratories must meet to conduct SVT for federal employee testing. The DOT instituted mandatory SVT for its drug testing programs in August 2008.

Under the SAMHSA guidelines SVT consists of

1. Measurement of the creatinine level;

2. Measurement of the specific gravity if the creatinine level is less than 20 mg/dL;

3. Measurement of the pH;

4. One or more screening tests for oxidizing adulterants.

5. Additional validity tests if these are observed:

a  Abnormal physical characteristics;

b. Reactions or responses characteristic of an adulterant;

c. Possible unidentified interfering substance;

If the certified laboratory cannot perform the additional tests required no. 5 above the laboratory will consult with the MRO to decide whether or not to send the specimen to another certified laboratory to complete the testing.

Reporting of the laboratory results of SVT is summarized in the SAMHSA-issued grid (Figure 1~2} 662).

In summary, when Sky is done, results with no SVT findings on any of the tests are reported simply as negative or positive. If there are SVT findings, the results may still be negative or positive, but additionally they also may be dilute or invalid. In cases where the laboratory can confirm extreme dilution or the presence of an adulterating substance, the results are reported as substituted or adulterated, respectively.

Here are the definitions of each:

Adulterated specimen: A specimen that contains a substance that is not expected to be present in human urine, or contains a substance expected to be present but is at a concentration so high that it is not consistent with human urine.

Dilute specimen: A specimen with creatinine and specific gravity values that is lower than expected for human urine.

Invalid drug test: The result of a drug test for a urine specimen that contains an unidentified adulterant or an unidentified interfering substance, has abnormal physical characteristics, or has an endogenous substance at an abnormal concentration that prevents the laboratory from completing or obtaining a valid drug test result.

Substituted specimen: A specimen with creatinine and specific gravity values which are so diminished that they are not consistent with human urine.

For a specimen to be reported as adulterated or substituted the laboratory must adhere to the same requirements as it does to report a drug positive. In other words, both screening and confirmation tests must be conducted, and the result must be the same for each.

For the laboratory to report either a negative or a positive specimen as dilute, both creatinine and specific gravity must be in the dilute range as shown on the grid. Positive dilute specimen results are handled as any other positive would be, with no change because the specimen is dilute.

The DOT and HHS have differing requirements for the handling of certain dilute negative specimens. If the creatinine is less than or equal to 5 and the specific gravity is in the dilute range but not substituted, DOT requires the MRO to inform the employer that an immediate observed recollection must be conducted. HHS simply treats this as a dilute specimen. In neither case does the MRO interview the donor.

DOT also allows employers the option of ordering a specimen recollection 1 time when a test is reported as negative dilute. Only 1 recollection is allowed, and if that collection results in another negative dilute the employer is required to accept that result as a negative. Although all employees must be treated alike in these requirements the employer may elect not to implement the requirement for all reasons for testing. In other words, the employer may elect to do this for pre-employment but not for random testing.

When the laboratory reports an invalid result the causes may be many and varied. Creatinine and specific gravity disparities may be reported as invalid; screening or confirmation abnormalities may cause an invalid result. It is essential that the MRO and the certifying scientist be in contact with each other to discuss and come to a mutual understanding about invalid results. An invalid result from the laboratory is reported by the MRO to the employer as a canceled drug test. Along with a canceled test determination, the MRO must report the reason the test was cancelled and whether a recollection of a specimen is needed, and if it is to be conducted under direct observation.

Invalid results often are the result of screening or confirmation test interferences. Screening interferences are frequently caused by prescription medications, but not always. An older commercial adulterant product called glutaraldehyde also produces immunoassay interferences, but the certifying scientist should be able to advise the MRO whether that is the probable cause. For likely prescription medication interferences, the MRO may order a different immunoassay screen if the laboratory is able to perform one. Prescription medications that are likely causes include tolmetin sodium, quinolone antibiotics, metronidazole, and others. When the MRO learns of an invalid result that may have been caused by a prescription, he or she should conduct a normal donor interview and verify the prescription. When the prescription is verified, the result is a canceled test and the recommendation is an unobserved recollection if a negative result is needed as in pre-employment, return to duty, and follow-up testing. When a negative result is not needed, recollection is not necessary.

Interferences with confirmation testing, however, are almost always caused by some form of adulterant added to the specimen during the collection, and are frequently accompanied by a loss of the laboratory’s internal standard. Oxidizing adulterants interfere with marijuana confirmation and cause loss of the laboratory’s internal standard. Unfortunately, if there is blood in the urine specimen, as there may be during menses or lower urinary tract infections, that blood contains per-oxidase, which is also an oxidizing agent. MROs should ask the certifying scientist who reports that an oxidizing agent interfered with the confirmation to also test the specimen for blood. If the donor history is consistent with the appearance of blood in the urine specimen, an unobserved recollection should be requested as discussed above. Absent blood in the urine, oxidizing agents and other confirmation interferences are canceled tests, with the MRO advising the employer that an immediate observed recollection is mandatory.

If the certifying scientist tells the MRO that it appears the result is likely caused by an adulterant that another laboratory might be able to identify, the MRO can order the specimen be sent to another DHHS certified laboratory for more testing. If the reference laboratory cannot confirm the adulterant, an observed recollection must occur, and enough time has passed that the donor may have been able to metabolize away whatever he or she might have been trying to hide in the first place, producing an observed recollection with a negative result. The employer will also have to pay the multiple charges. The MRO may wish to consider simply expediting the observed recollection immediately instead of going through such a prolonged testing scenario.

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