Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (631 page)

   Oral fluid (saliva)

   Sweat

   Hair

The majority of hospital laboratories do not offer testing in these specimens. Sample pretreatment prior to testing is often required and, therefore, are not offered on a “stat” basis. Special sample collection devices are available for sweat and oral fluid. Hair testing provides a longer detection window for drugs than does serum or urine and is generally reflective of chronic exposure.

   Units

Drugs concentrations are reported using several concentration units.

   ng/mL, which are equivalent to mcg/L

Note that “mcg” are used throughout this text because “ug” or “μg” are prohibited abbreviations. When handwritten the “u” may be misread as “m.”

   mcg/mL, which are equivalent to mg/L

Note that ethanol concentrations in the clinical setting are typically reported in mg/dL. Conversion to g% (g/dL) is often requested; for example, 80 mg/dL is equivalent to 0.08 g/dL. To convert mg/dL to g/dL, divide by 1,000. Conversely, to convert g/dL to mg/dL, multiply by 1,000.

   
ADDICTION MEDICINE

   Purpose

Provision of professional health care services to treat a diagnosed substance use disorder

   Application

Drug testing during treatment to assess and monitor the clinical status of an individual. Testing should be limited to that which is medically necessary. Testing is appropriate in inpatient and outpatient settings and is especially important at the beginning of treatment. Periodic random drug testing in this population may act as a deterrent to substance use and aids in identifying lapses in treatment. In addition, such testing may identify compounds that have potential drug interactions with a prescribed medication.

   Screening Methods and Limitations

   Point of care or laboratory immunoassay tests are the most common screening tests utilized.

   Urine, serum, oral fluid, and hair are all potentially useful specimens to monitor drug abstinence or compliance with prescribed medications.