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Procuring samples to avoid adulteration 

Drugs Of Abuse PillsSpecial precautions are required when collecting urine samples for “drugs of abuse” testing as adulteration or substitution is a distinct possibility in this field of work.

The basic requirement is a freshly voided random urine sample of AT LEAST 15mL. The sample must be clearly labelled with the patients': Full name, Date of Birth and specimen date.

The temperature of a freshly voided urine sample should be in the range of 32-38°C. If the sample feels cold when held in the hand, then substitution or adulteration should be considered and noted on the accompanying request form. 

Top tips

When collecting the sample, try to ensure that it is produced in an area where sources of adulteration are not readily available: - 

  • Where possible a toilet water colouring agent should be used to discourage adulteration of urine samples using toilet water.
  • Hand washing facilities should be outside the toilet/cubicle where the urine collection takes place. This is to avoid adulteration by addition of soaps or tap water.
  • Outer garments, coats, bags etc should be left outside the toilet during urine collection. This is to avoid the concealment of adulterants and/or substitute urine samples.

In order to assist the laboratory in preparing the report, all prescribed medicines should be detailed on the request form, together with details of suspected abused drugs.

The final report will consider whether any form of adulteration is likely to have taken place, such as dilution or "spiking" with methadone (in an attempt to "mask" a reduced ingestion;). Such integrity checks include visual inspection in addition to assessment of urinary creatinine (which should exceed 1.8mmol/L,) an osmolality >80mmol/kg and pH in the range: pH 4.0 - pH 9.0.

Last updated: 25 February 2016