SPECIALIST PHARMACOLOGICAL & BIOCHEMICAL INTERVENTIONS
URINE TESTING
Urine drugs of misuse testing remains the mainstay of testing in specialist drug and alcohol units, despite its many drawbacks in terms of inconvenience, adulteration of samples, observation of sample production etc.
1. On-site (rapid) urine testing.
There are several factors to consider when selecting a rapid test:
- The range of drugs tested for - specialist units should routinely test for opiates, methadone, cocaine, amphetamines, benzodiazepines and cannabis. An on-site urine screen is now available for detection of buprenorphine.
- Ease of use and interpretation of results - this is particularly important in a busy clinic - errors will be made frequently if the equipment is complex to use, if it is difficult to interpret the test and if there is a long duration required for the reaction to take place.
- The accuracy of the test - this will never match laboratory techniques and accuracies of below 90% should be regarded as unacceptably low.
- Cost.
An on-going European study of the utility of roadside testing (ROSITA) (Gronholm & Lillsunde, 2001) has provided information
regarding the accuracy and ease of use of a number of on-site urine immunoassays. Of those tested, Surescreen (Surescreen Diagnostics Ltd., UK), Rapitest Multidrug (Morwell Diagnostics, GmbH, Switzerland) and Status DS (Lifesign, LLC, USA) were found the easiest to use and interpret.
Taking into account all the above factors, Surescreen and Rapitest Multidrug would both appear suitable tests for use in specialist units. The Multidrug test offers a shorter reaction time which may be of significance in a busy unit. Status DS suffers from the major drawback of failing to detect benzodiazepine misuse. Whilst specificities are high (in the region of 98%) for all the devices, sensitivities tend to be a little lower (around 90%) apart from cocaine for which there is a high sensitivity.
2. Laboratory urine testing.
A laboratory test should always be used to confirm opiate misuse before commencing opiate substitute medication, and at any time if there is doubt as to the validity of the result given by an on-site test. Services should only contract with laboratories which offer GC/MS. Laboratory testing (in particular GC/MS) may also be used to test for the presence of almost any other substance which may be impacting on the clinical picture; e.g. confirmation of the use of an antidepressant may be sought, or a search for ingestion of substances which may be altering plasma methadone levels.
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The above information is copyright of Dr Bruce Trathen MBBS MRCPsych (2006). ISBN 0-9545164-0-0. The author grants permission for these guidelines to be downloaded, copied and distributed freely, but does not grant permission for their sale.
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