Adulterated and substituted specimens
Over the past decade increasing attention has been paid to attempts to ‘beat the drug test’. There have always been donors who have attempted this through diuresis, through substitution of the specimen (with clean urine or another fluid) or through deliberate adulteration of the collected specimen. The DOT first issued guidance on this in 1992 and recommended that laboratories identify adulterants in a ‘forensically acceptable manner’. A ‘dilute urine specimen’ was defined as one that contained less than 20 mg/dL creatinine and had a relative density (specific gravity) of less than 1.003. At that time regulations allowed an observed urine collection on a donor producing dilute urine at their next scheduled collection, and at the request of the employer. In practice this was hardly ever done. Collection guidelines also required the collector to perform an observed collection if there were suspicious circumstances during collection or if the urine temperature was out of range (the acceptable range being 32.2 to 37.7C). In recent years use has been made of the internet to sell products that are supposedly designed to beat the drug test. Whereas a number of these include the instructions to drink copious amounts of water before taking the test (i.e. diuresis), others are designed specifically to oxidise the THCA metabolite of cannabis and thereby reduce the ability of the laboratory to confirm cannabis use. Some examples of substances sold to prevent detection of a sample likely to test positive include nitrite, chromate (CrVI), halogens and peroxide.
Although accurate data are difficult to obtain, a relatively recent estimate shows that at least 0.05% of the specimens tested for federally mandated purposes are adulterated (Kadehjian 2001). If so, this would be similar to the positive rate for some drugs, for example the amfetamines and PCP. The recently published CFR Part 40 (Federal Register 2000) requires certified laboratories to detect adulterated and substituted specimens. The HHS has issued detailed proposed rules (2004) for such testing, which include definitions and the testing and quality control procedures to be used. Steps that the medical review officer (MRO) can use for review of these non-negative specimens are also included. The definitions for a dilute, substituted and adulterated specimen are as follows:
• dilute: creatinine less than 20mg/dL and relative density less than 1.003, except when the definition of a substituted specimen is met
• substituted: creatinine less than 2 mg/dL and relative density less than 1.002 or equal to or greater than 1.020.
• adulterated:
– nitrite is greater than or equal to 500 lg/mL
– pH is less than 3 or greater than or equal to 11
– specimen contains an exogenous substance (i.e. a substance that is not a normal constituent of urine)
– specimen contains an endogenous substance at a concentration greater than that considered to be a normal physiological concentration.
The other definition included in the rules is for an invalid drug test, which, among others, includes one in which the laboratory has failed to identify the adulterant. These rules are interesting for a number of reasons. Firstly, a workplace drug-testing laboratory now has to perform tests that, historically, have not been performed in toxicology laboratories. Secondly, the toxicologist and/or MROmay be called upon to defend this specimen validity testing procedures and their results when legally challenged, for example in an arbitration hearing. Defending a non-negative result may present new challenges in terms of the interpretation of the data. Thirdly, they expand the duties of the laboratory to include the identification of new and existing adulterants, which is a major analytical challenge. Finally, they are the first such rules to prescribe quality-control protocols for diluted, adulterated or substituted specimens.
According to the SAMHSA rules, in addition to performing creatinine tests on all specimens, a certified laboratory has to perform pH testing on all specimens, validity tests for substances that are commonly known as oxidising adulterants, and additional validity tests when one of three further conditions are observed (SAMHSA 2002). This brief overview of some of the newer requirements and of the expansion of the programmes to include alternative specimens demonstrates that the range and complexity of workplace drug testing has increased dramatically and will continue to do so.
