What is the difference between presumptive and confirmatory toxicology tests?

What is the difference between presumptive and confirmatory toxicology tests?

• A. Presumptive tests indicate possible presence; confirmatory tests provide definitive identification.
• B. Presumptive tests are slower than confirmatory.
• C. Presumptive tests are more accurate than confirmatory.
• D. There is no difference.

Answer: (A)

Presumptive tests are screening tools that indicate the possible presence of a substance, delivering rapid, preliminary results without proving the exact identity. Confirmatory tests use highly specific methods, such as GC-MS or LC-MS/MS, to provide definitive identification (and often quantification) by matching a substance’s unique chemical signature. Because presumptive tests can react with similar compounds or be affected by interferences, they may yield false positives or negatives, which is why a follow-up confirmatory test is required to make a definitive determination. In practice, scientists screen first with a quick presumptive test and then apply a confirmatory test to establish with high certainty what, if anything, is actually present.