Frequently Asked Questions?

Methamphetamine isomer testing helps determine if a positive methamphetamine confirmation is illicit.  Methamphetamine is produced as two isomers.  The D isomer (dextro- or D-methamphetamine) is a powerful central nervous system stimulant and commonly abused street drug known as “meth” or “speed”.  D-methamphetamine is also the primary active component of Desoxyn, a medication sometimes used to treat ADHD and obesity.  The L isomer (levo- or L-methamphetamine) is not a central nervous system stimulant and is not controlled by the DEA.  Vicks Vaporub is a common example of a medication containing L-methamphetamine.  Federal drug testing policies state that urine containing more than 20% D-methamphetamine is consistent with exposure to the DEA controlled version of the drug and is likely due to illicit use if the patient is not prescribed a D-methamphetamine containing drug such as Desoxyn.

Most drugs are processed by the body to produce “metabolites”, which can be active or inactive compounds, that were not present in the parent drug prior to administration.  We include relevant metabolites of common drugs in our panels for two reasons:

1. If a parent drug is metabolized quickly and the urine sample is collected far after the most recent dose, the parent drug may have been fully metabolized and thus may not be present in the sample.  Testing for metabolites allows us to confirm the patient is taking a drug even when the drug in question is not detected.
2. Patient samples can be adultered to test positive for a drug which is not being taken as prescribed.  One method for this is through the addition of pill scrapings into a urine sample so the sample will test positive for the parent drug, in an attempt to mimic a positive test.  When metabolites are tested alongside the parent drug, it can readily be ascertained when a sample has been adultered through the presence of high concentrations of parent drug with no or very low levels of metabolites.

Note: substantial variability exists in metabolic rates and renal clearance between individuals, and even medication changes may influence the ratio of metabolites to parent drug.  In some cases this may even cause certain metabolites to be absent from the sample.  Hydrocodone, for example, is metabolized into hydromorphone, norhydrocodone, and dihydrocodeine.  If a patient is prescribed fluoxetine (Prozac), the amount of hydromorphone produced following hydrocodone administration will be reduced dramatically, sometimes below the level of detection.  This patient would still have parent drug (hydrocodone) as well as the other metabolites (norhydrocodone and dihydrocodeine).  Please contact our technical support staff for a more detailed explanation of a specific sample or for a more general review of how to consider metabolite concentrations alongside parent drug concentrations.

In a complex biological specimen, analytical interference may occur in which high levels of one compound may influence the ability of the method to identify another compound.  A relevant example from our panel is the influence of gabapentin on amphetamine measurement.  Patients receiving gabapentin can produce urine concentrations so high that they completely mask the ability to measure amphetamine in the sample.  Further, methamphetamine is metabolized by the liver into amphetamine, therefore all samples positive for methamphetamine should have amphetamine present as well.  High levels of urine gabapentin may mask urine amphetamine, resulting in a sample reported positive for methamphetamine but negative for its metabolite, amphetamine.  Please contact our technical support staff with any questions regarding amphetamine measurements in patients receiving high-dose gabapentin.

Several sample types exist for serial drug monitoring, including blood, urine, oral fluid and hair testing.  Urine is the preferred sample in many cases because it offers a non-invasive collection method, is usually a plentiful sample type, and collection of urine poses minimal risk to the patient and staff.  Urine drug analysis detects presence of a compound longer than analysis in blood and at lower concentrations than hair analysis.  Time from sample collection to results is equivalent to blood analysis and significantly shorter than hair analysis.  Urine as a sample type, however, is not without drawbacks.  Urine measurement will not detect drug after ingestion or injection as rapidly as blood analysis, nor will it detect historical drug use as long after cessation as hair analysis.  Finally, urine drug analysis is not subject to the same drastic shifts in concentration between doses as exhibited by blood sampling, but it is therefore not as useful at therapeutic drug monitoring as blood analysis.  All considered, due to the ease of collection and good rates of positivity after cessation of a drug, urine is the preferred specimen type for drug screening and confirmation.

Collecting a urine specimen may sometimes pose undesirable complications for patients who are unable to urinate at the time of the appointment or are suspected of tampering with the specimen. In these cases, Bluewater offers drug monitoring on oral fluid, a specimen type readily available and the collection of which can easily be observed.

Creatinine is a byproduct of muscle metabolism and is excreted at a relatively constant rate from the kidneys.  While the volume of urine produced in a given period of time can change dramatically with over- or under-hydration, resulting in more or less concentrated urine, the amount of creatinine excreted per hour is a factor of blood flow through the kidneys and thus remains relatively constant for a given patient.  Due to its relative stability, creatinine is an excellent analyte to use for normalization of all analyte concentrations within a sample, which affords providers some level of comparison between samples.  Creatinine is normalized to a “standard” concentration of 100 mg/dL, so that historical values reported for a given patient can be compared relative to each other, regardless of the patient’s level of hydration at the time of each sample collection.  For example, if one sample had a creatinine value of 50 mg/dL, all analyte concentrations for the sample would be doubled to achieve a “normalized” value equivalent to 100 mg/dL creatinine.  Likewise, if a creatinine value was 200 mg/dL, all the analyte concentrations would be halved to achieve a “normalized” value equivalent to 100 mg/dL creatinine.  Further, creatinine also affords an additional element to evaluate sample integrity, as extremely low creatinine concentrations not within physiological levels can be a sign of sample adulteration.

• Quantity not sufficient for testing
  The preferred sample volume is 10mL, however analysis can be completed with as little as 2mL.  Any specimen received with less than 2mL total volume will be rejected and marked QNS for “Quantity not Sufficient”.
• Specimen improperly labeled/identified
  All specimens received for analysis must be labeled with at least 2 patient identifiers consisting of the following: (1) name, (2) date of birth, (3) social security number/medical record number/patient identification number, and (4) requisition number (or other special identification number).
• Specimen leaked in transit
  If a leaked specimen is delivered to the laboratory with insufficient volume for testing, or if a leak has caused possible cross-contamination, the specimen(s) will be rejected as “Specimen Leaked in Transit”.
• Specimen found to be adulterated
  Sample integrity analysis measures specific gravity, creatinine, nitrite, pH, and oxidants.  In addition, ratios of parent drug concentrations to metabolites may suggest adulteration of a sample even if other markers are within physiological limits.  These situations are considered on a case-by-case basis.
• Specimen exceeds stability requirements
  Analytical parameters of our method are only verified for samples collected and stored as directed.  This includes storage for up to 14 days at room temperature, 30 days refrigerated and 60 days frozen.  Any specimen exceeding these storage limits will be rejected.

At Bluewater, we perform both urine screening and confirmation tests for prescribed medications and illicit drugs.  Screening tests utilize immunoassays to rapidly detect drug classes, but in most cases cannot differentiate between specific drugs of a class or the metabolites produced by the body when those drugs are consumed.  Screening tests typically have lower sensitivity than confirmatory testing.  Confirmation analysis utilizes liquid chromatography mass spectrometry to individually identify and quantify all relevant compounds in the sample from our list of 59 parent drugs and metabolites.  Confirmation analysis is more time consuming than screening, but it is considered the gold standard for analysis of compounds in urine.