Agreement in drug identification does not guarantee agreement in measured concentration.
A postmortem study compared two dried-blood substrates with liquid cardiac blood. Qualitative identification corresponded well, but alprazolam, diazepam and desmethyldiazepam were among compounds showing lower concentrations on one card type.
The sample was small and postmortem, with specific extraction and storage conditions. A general correlation can conceal analyte-specific bias. Results cannot automatically be transferred to living-patient samples or different card preparations.
Record the substrate, extraction and validated analyte scope. A lower card result need not reflect a lower original blood exposure. Do not treat a qualitative match as proof that numerical results are interchangeable when interpreting a concentration-based opinion.
Source: PMC7812343, supplied full-text paper. Findings are paraphrased; forensic implications are an interpretation.
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