Step-by-Step Guide to Interpreting Opiates Screening Test Results

Step 1: Enter Results of Opiates Test

The first step is to examine the test results as reported by your lab:

  • Opiates Test Result:
    • Negative: No opiates detected at the thresholds set by the test.
    • Positive: Opiates detected, which may indicate the presence of one or more substances in the opiate class.
  • Oxycodone Test Result (If specifically tested):
    • Negative: No oxycodone detected.
    • Positive: Oxycodone detected.

Step 2: Select Opiates Prescribed or Illicit Drugs Used

List the substances that have been prescribed to your patient or those that the patient may be using, including illicit drugs. This helps in identifying potential cross-reactivity between different opioids. Some common opioids that can show up on an opiates screening test include:

  • Buprenorphine (Suboxone, Subutex)
  • Codeine (Tylenol #3, Tylenol #4)
  • Fentanyl (Duragesic, Actiq)
  • Hydrocodone (Vicodin, Norco)
  • Hydromorphone (Dilaudid)
  • Heroin (MAM-6) (Heroin metabolite)
  • Meperidine (Demerol)
  • Methadone (Dolophine)
  • Morphine (MS Contin, Kadian)
  • Oxycodone (Percocet, Roxicodone)
  • Oxymorphone (Opana, Numorphan)

Step 3: Click ‘Interpret’

After inputting the test results and the substances in use, you should click on “Interpret” to get a preliminary interpretation based on the data you’ve entered.

Step 4: Review Recommendations

The next step is to review the interpretation and recommendations based on your patient’s history and the test results. The interpretation should be based on the following factors:

Key Considerations for Interpretation

1. Cross-Reactivity Between Drugs

Certain opioids can cross-react with others during screening, leading to false positives or unexpected results. Here are a few key points to keep in mind:

  • Semisynthetic Opioids (Hydromorphone, Oxymorphone, Hydrocodone, Oxycodone): These can be particularly tricky as they are often metabolized into each other. For example, hydrocodone might be metabolized into hydromorphone, which could show up on the test as hydromorphone.
  • Codeine and Morphine: Morphine and codeine are closely related. If a patient takes codeine, the test might show a positive for morphine, especially if they take high doses.
  • Buprenorphine: This drug is a partial agonist and may not show up on a standard opiates screening test. Confirmatory tests are often required to accurately identify buprenorphine use.

2. Detection Windows and Test Sensitivity

Different drugs have varying detection windows, which affect the results:

  • Short-acting opioids (e.g., oxycodone, hydrocodone) may be detectable for 1-4 days.
  • Long-acting opioids (e.g., methadone, fentanyl) may be detectable for up to 10 days.
  • Heroin (MAM-6) and its metabolite 6-acetylmorphine (6-AM) typically show up in 1-3 days after use.

Keep in mind that patients on low doses of opioids may have lower concentrations in their urine, decreasing the likelihood of a positive test. On the other hand, chronic users or those on high doses may have higher concentrations, which may affect the results.

3. False Positives and False Negatives

Certain substances can cause false positives or false negatives on opiate screening tests, such as:

  • False Positives:
    • Poppy seeds can lead to a positive result for morphine.
    • Dextromethorphan, a common cough suppressant, can cause false positives for hydrocodone and tramadol.
    • Diphenhydramine, a common antihistamine, can lead to false positives for hydrocodone and morphine.
  • False Negatives:
    • Low doses of opioids or immediate-release formulations may result in false negatives, as the urine concentration might be below the detectable threshold of the screening test.
    • Improper timing of the test (e.g., testing too soon or too late after opioid use) can lead to false negatives.

4. Prescribed vs. Illicit Use

It’s essential to differentiate between prescribed opioids and illicit use (e.g., heroin or fentanyl). If the test shows positive for morphine and the patient is prescribed morphine, the result is expected. However, if the test shows positive for morphine and the patient has never been prescribed it, it could indicate illicit heroin use, especially if 6-acetylmorphine (6-AM) is detected.

Similarly, a positive result for oxycodone could suggest either the prescribed medication or illicit use of oxycodone.

Clinical Recommendations for Action Based on Test Results

After reviewing the test results and understanding the potential factors at play, here are some general clinical recommendations:

  1. If Negative:
    • Ensure the patient is still taking the prescribed medication, or confirm that they are adhering to the treatment plan. A negative test result could suggest non-adherence or insufficient dosage for detection, but it could also indicate misuse of non-prescribed substances.
  2. If Positive:
    • Review the medication prescribed and any potential cross-reactivity with other drugs.
    • Consider a confirmatory test (e.g., GC-MS or LC-MS) for definitive identification of the substances detected, especially if the results do not match the prescribed medications.
    • If illicit drugs are suspected, take appropriate action based on the patient’s medical history and treatment plan.
  3. If Confused by Cross-Reactivity:
    • Consult with a pharmacologist, toxicologist, or your local clinical lab to clarify the results. This is especially important in patients on multiple medications or polypharmacy regimens, as cross-reactivity between drugs (e.g., semisynthetic opioids) is common.

Conclusion

Interpreting opiate screening test results is complex, and it’s important to consider both the test results and the patient’s prescribed medications or illicit drug use. This should be done in consultation with your local clinical laboratory, especially if the results are ambiguous or unexpected. Always use additional confirmatory tests for precise identification, and consider cross-reactivity and metabolism factors that can influence the test outcome.

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