11 - Laboratory investigations for assessment and management of drug problems

Summary

Summary Much of the drug testing available today is able to determine the presence or absence of a variety of psychoactive substances in a range of body fluids and tissues. For the results of such tests to be confidently interpreted, additional information is required, including general assessment and history-taking. In a wide range of large psychiatric surveys, substance dependence emerges as one of the most common mental health-related disorders, and it is also the one that is least likely to be treated. The range of available tests can be best considered as acting to support and complement a broader assessment and diagnostic procedure.

The aim of this chapter is to outline the variety of laboratory investigations available that could be considered as biological indicators of substance use and misuse. We will review the strengths and weaknesses of different approaches and different body matrices (urine, blood/plasma monitoring, oral fluid and hair testing), along with other possible materials not usually considered, with a focus on the clinical usefulness of these procedures.

A drug may be detected in any body fluid or tissue, but there are practical limitations to the extent to which samples can be and are used, and the mechanism of collection and supervision of samples are critical to the procedure.

Chain of custody

The procedure of ensuring that an identified sample was provided by a specified individual (chain of custody), and has subsequently been correctly labelled to ensure accuracy, must be properly documented. In the case of urine samples, chain of custody procedures usually require the collection to be witnessed by a designated member of staff (clinician, nurse, drug worker, therapist, etc.) and written confirmation of its validity from the individual voiding the sample, as detailed in Box 11.1 (Wolff et al, 1999a).

Box 11.1 Chain of custody procedures for urine samples

• Before, during and after urination, collection site personnel must keep the urine specimen in sight

• The urine container must be tightly capped, properly sealed and labelled with the patient/client's name and the time and date of collection

• To maintain accountability the approved chain of custody form must be used and it must accompany the sample from initial collection to final disposition

• Reliable transportation (courier system) to the laboratory must be used