Investigations
1st investigations to order
urine or saliva drug screen
Test
A drug screen should be ordered initially if there is a clinical suspicion of drug use.
The Drug Screen 9 (DS-9) is one of the more common immunoassays, and tests a urine sample for opioids (oxycodone, hydrocodone, hydromorphone, morphine, and codeine only), cocaine, marijuana, benzodiazepines, phencyclidine, amfetamines, and barbiturates.
The test will report 'positive' for opioids in opioid abusers; however, it will not specifically identify which opioid has been taken.
A point of care test (POCT) on a urine or saliva specimen may alternatively be performed as the initial screening test in certain circumstances (e.g., in primary care). The principal advantage of POCTs over laboratory screening tests is that the results are available in approximately 10 minutes. This fast turnaround allows practitioners to discuss the results with the patient during that office visit, and make clinical decisions and act appropriately that day. POCTs are also inexpensive and relatively easy to use with minimal training. Despite these benefits, laboratory testing is more accurate overall, and provides quantitative estimates of drugs and their metabolites.[43]
Routine immunoassays do not usually detect synthetic or semisynthetic opiates (e.g., fentanyl, methadone, propoxyphene, meperidine, tramadol, pentazocine) and so a positive urine or saliva screen should be followed by a confirmatory urine test.
Result
positive (cut-off limit 300 nanograms/mL)
gas chromatography-mass spectroscopy (GC-MS)
Test
Positive urine or saliva screen should be followed by a confirmatory urine test due to opioid sensitivity limitations and because certain medications (e.g., antibiotics) can interfere with the test and produce false-positive results.
Opioid confirmation urine test by GC-MS is the most specific and sensitive test for identifying opioids.
Will identify the specific opioid in the urine.
There are specialised GC-MS tests to detect fentanyl and buprenorphine.
It is important to note that heroin will be detected as morphine in the urine, and a specific metabolite of heroin (i.e., 6-monoacetylmorphine) that is only detectable for a few hours after heroin use has to be identified to distinguish heroin from morphine use.
Result
positive (cut-off limit 150 nanograms/mL)
serum electrolytes
Test
May be deranged secondary to malnutrition associated with opioid use.
Result
normal or deranged
FBC
Test
Useful to identify presence of infections from illicit intravenous drug use and to evaluate baseline for follow-up as part of the general haematological profile.
Result
WBC count is normal or elevated in presence of infections
urea/creatinine
Test
Evaluation of renal function is necessary for dosing of medications.
Result
normal or elevated in presence of renal impairment
LFTs
Test
Evaluation of liver function is necessary for dosing of medications, as well as to direct appropriate intervention for existing liver disease.
LFTs are often elevated due to hepatitis or from injury to the liver caused by contaminants in the injected opioid.[1]
Result
normal or elevated in presence of hepatic impairment
hepatitis serology
Test
Testing for hepatitis B and hepatitis C infection is recommended in all patients by the American Society of Addiction Medicine.[46]
Intravenous drug abuse is associated with hepatitis B and C infection.
Result
normal or positive in presence of hepatitis B virus or hepatitis C virus infection
HIV serology
Test
Testing for HIV infection is recommended in all patients by the American Society of Addiction Medicine.[46]
Intravenous drug abuse is associated with HIV infection.
Result
normal or positive in presence of HIV infection
purified protein derivative (PPD) skin test
Test
Testing for tuberculosis infection is recommended in all patients by the American Society of Addiction Medicine.[46]
Immunity is decreased in intravenous drug users, leading to either reactivation of latent tuberculosis or increased susceptibility to infection.
A positive result indicates tuberculosis exposure.
A result of 10 mm or more is considered to be positive in intravenous drug users. If HIV-positive, a result of 5 mm or more is considered to be positive.
Result
normal or positive (5 to 10 mm) in presence of tuberculosis infection
Investigations to consider
rapid plasma reagin
Test
Testing for sexually transmitted infections such as syphilis should be considered.
Intravenous drug abuse has been associated with a positive rapid plasma reagin test.
Result
normal or positive in presence of syphilis
blood cultures
Test
Indicated if there are signs or symptoms suggestive of septicaemia (e.g., high fever, altered mental state, and vital sign changes) or infective endocarditis (e.g., fever with heart murmur).
Result
normal or positive for staphylococci, streptococci, or Pseudomonas aeruginosa
beta human chorionic gonadotrophin (beta-hCG)
Test
All women of childbearing potential should be tested for pregnancy.[46]
It is important to rule out pregnancy for appropriate use of medications, and to evaluate the risk of neonatal opioid withdrawal syndrome.
Result
normal or positive in pregnant women
Use of this content is subject to our disclaimer