Presumptive Versus Definitive Testing

There are 2 types of drug testing—presumptive and definitive.

Presumptive
  • Identifies possible use or non-use of drugs or drug classes, and includes point-of-care (POC) and laboratory immunoassay (IA) methods
  • Results are reported qualitatively (Negative or Positive), and does not identify drugs/metabolites
  • Includes lab-based immunoassay and presumptive mass spectrometry methods of analysis
  • Requires definitive mass spectrometry to identify drug/metabolite present
Definitive (Quantitative) UDT
  • Identifies specific drugs/metabolites present
  • Used to confirm presumptive results and rule out false-positive presumptive results
  • Used to identify specific substances or metabolites that are not detected by presumptive methods, including gabapentin, pregabalin, tapentadol, tramadol, synthetic cannabinoids, and other synthetic/analog drugs
  • Used when a definitive concentration of a drug is needed to guide management (e.g., discontinuation of THC use according to a treatment plan)
  • Drugs/metabolites can be reported as either the name (qualitative) or the name and concentration (quantitative)

 
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When to use presumptive with definitive UDT:

In general, best practices include presumptive testing and confirming unexpected positives or negatives with definitive testing, as well as direct-to-definitive testing when a presumptive test for a specific drug is not available.

  • Presumptive test panels can provide initial results that can be confirmed with definitive testing
  • Definitive is used to identify a specific drug that is inadequately detected by a presumptive test
  • Definitive is used to identify specific drugs or drug metabolites
  • Definitive testing is used when a presumptive test for a drug or drug class is not available

Data shows that when performing this 2-step presumptive with definitive testing approach, we find that on average only 2.5 drugs need to be reflexed to definitive, which maximizes patient care while minimizing costs.

In those cases when POC testing is needed, definitive testing can be used to confirm the results.