Examination and investigations in assessing substance use and addictive behaviours

A general physical and mental state examination may identify signs of:

• intoxication, withdrawal or comorbid mental illness—identification of psychosis or marked paranoia is essential in assessing a person’s decision-making capacity and the risk of serious harm to them and others. For advice on informed consent and assessing capacity, see Informed consent and shared decision-making in a person with a psychiatric disorder
• organ damage from substance use
• dental disease (caused by lack of oral care or drug effects such as dry mouth, tooth grinding and vascular damage to gums)
• malnutrition
• injecting-related harms (eg viral or bacterial bloodborne infections)
• pregnancy
• sexually transmitted infections.

Investigations can support treatment decisions but are generally not useful as screening tools.

Investigations to consider when assessing substance use include tests to detect:

• substance-specific organ damage—liver biochemistry is useful to assess the effects of alcohol use on the liver (but is insensitive as a screening test for alcohol use)
• harms associated with the route of use such as injecting harms, including site infections (eg cellulitis, fasciitis, abscesses) and bloodborne infections (eg hepatitis B, hepatitis C, HIV, bacterial endocarditis); infections can also result from using pipes and bongs (water pipes) but this is less common
• consequences of other risky behaviours such as unprotected sexual intercourse (eg sexually transmitted infections, unplanned pregnancy).

For some disorders of substance use, specific investigations should be considered before starting drug therapy; these are discussed in the specific topics.

Routine urine drug screening is not generally required in primary care, but discussing its role in treatment decisions and safe prescribing can open conversations about substance use. It can be useful to ask ‘If I did a urine drug screen today what would I find in your urine?’. Screening may be useful when transferring patient care, or may be required in specific situations (eg by child protection agencies, changing prescribers of medication- assisted treatment of opioid dependence). Testing specified by courts requires specific techniques and demonstration of a chain of custody of a sample. Interpretation of urine drug screens is complicated by factors such as false positives and negatives; advice from a pathologist is recommended before interpretation. Not all commonly prescribed drugs are part of a standard urine screen covered by the Medicare Benefits Schedule (MBS). Confirmatory urine drug testing is not reimbursed. Pathology costs may add financial burden for the patient; shared decision-making about testing is recommended. Before ordering a urine drug screen, determine the availability, utility and cost from local pathology providers because these factors vary with location and over time.