Presumptive vs Confirmatory Test
Definition
A presumptive test (Reinsch for heavy metals, Marquis for opioids, Trinder for salicylates) is fast, cheap and class-specific, used to triage caseloads. A confirmatory test (LC-MS/MS, GC-MS, ICP-MS) identifies the exact molecule and quantitates it. An Indian FSL report does not name a poison on a presumptive result alone.
- Presumptive examples
- Reinsch, Marquis, Trinder
- Confirmatory examples
- LC-MS/MS, GC-MS, ICP-MS
- Presumptive role
- Fast, cheap triage of caseloads
- Confirmatory role
- Exact molecular identification and quantitation
Common questions
Why does an Indian FSL report withhold a poison name until confirmation?+
A presumptive colour or spot test can be positive for a whole class of compounds, so naming a specific poison from that result alone risks a wrong identification. Laboratory protocols hold the identification back until a confirmatory instrumental method has pinned down the exact molecule.
Can a confirmatory method be used without a presumptive screen first?+
Yes, but screening first is standard practice because instrumental confirmation is slower and more expensive; running a cheap presumptive test on every sample lets the laboratory prioritise which samples go onto the mass spectrometer.
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