Confirmatory Hierarchy
Definition
The structured sequence of tests applied to biological evidence, in which a presumptive (screening) test with high sensitivity is followed by a confirmatory test using a different analytical principle, requiring concordant results before a conclusion is reported.
- Field
- Forensic serology
- Stage 1
- Presumptive (screening) test, high sensitivity
- Stage 2
- Confirmatory test, different analytical principle
- Reporting rule
- Requires concordant results at both stages
Common questions
Why must the confirmatory test use a different analytical principle from the presumptive test?+
If both tests relied on the same chemical mechanism, they would share the same false-positive triggers, so a substance that fooled the first test would fool the second too. Using an independent principle means a false positive at the screening stage is unlikely to also produce a false positive at confirmation.
What happens when a presumptive test is positive but the confirmatory test is negative?+
The hierarchy treats this as a discordant result, and the identification cannot be reported as confirmed. Analysts must report the presumptive finding for what it is, an indicator only, and either retest or note the substance as unidentified rather than reporting the presumptive result as definitive.
Related terms
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- False Positive
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- Hook Effect
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- Inhibitor
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