A quetiapine result reported as present below 0.10 mg/L is a positive identification with a quantitative limit. It is not a negative test, an exact concentration of 0.10 mg/L, or permission to assign another number below that boundary. A seven-case autopsy report illustrates how identification can remain useful when reliable numerical reporting stops.
What the seven-case report examined
Anderson and Fritz described quetiapine findings in seven Los Angeles County coroner cases. Heart blood was available in all seven, femoral blood in five, and other specimens in varying numbers. This was descriptive casework, not controlled dosing or an experiment defining a lethal concentration.
Specimens were collected at autopsy. Heart blood contained sodium fluoride; femoral venous blood contained sodium fluoride and potassium oxalate. Other matrices had no preservative, and all biological specimens were stored at 4°C. A uniform death-to-collection interval was not provided.
Presumptive screening and confirmation were separate
A basic extraction followed by gas chromatography with nitrogen-phosphorus detection, or GC–NPD, supplied presumptive identification. The investigators confirmed quetiapine by GC–MS comparison with a pure analytical standard. A second specimen aliquot was extracted for GC–NPD quantitation against known quetiapine quantities.
The reported quantitative range was 0.10–3.0 mg/L, with a quantitation limit of 0.10 mg/L. The authors explicitly stated that a detection limit had not been established. The quantitation limit therefore must not be relabeled as the method’s validated detection limit.
What the low findings actually said
Cases 6 and 7 had quetiapine reported as present but below 0.10 mg/L in both heart and femoral blood. The report used the notation “+<” for present below the stated level. That notation retained identity information without claiming a supported exact concentration.
The authors said a distinctive metabolite pattern helped identify quetiapine at these low levels. It did not turn the metabolite peaks into quantified metabolite concentrations or establish how long before death the drug had been taken.
These distinctions matter when results are summarized in a spreadsheet or expert report. Replacing the finding with zero discards the detection. Replacing it with 0.10 mg/L makes an upper reporting boundary look like a measured value. Choosing half the boundary would introduce an imputation that the case report did not perform.
The same detection did not imply the same death attribution
Case 6 was a 27-year-old woman whose death was attributed to cocaine toxicity. Case 7 was a 43-year-old woman whose death was attributed to acute cardiac dysfunction associated with hypertrophic cardiomyopathy. The low quetiapine finding did not make either death a quetiapine poisoning.
Across the series, five deaths involved multiple-drug intoxication, sometimes alongside another factor. No case supplied a controlled comparison of low quetiapine concentration with observed impairment. The authors’ descriptive use of “subtherapeutic” did not establish a universal postmortem safety boundary.
How to carry the finding forward accurately
Preserve the positive identification, specimen site, units, reporting symbol, quantitation limit and confirming method. Ask separately whether a numerical interpretation is supported and whether the whole investigation supports a causal role. Identification, quantitation and causation answer different questions.
For the opposite reporting boundary, see what a “greater than” fentanyl result means. That example does not supply quetiapine validation.
Primary source
Anderson DT, Fritz KL. Quetiapine (Seroquel) Concentrations in Seven Postmortem Cases. Journal of Analytical Toxicology. 2000;24:300–304. doi:10.1093/jat/24.4.300.
Leave a Reply