In the double-sampling technique for improving postmortem interval estimation, a second vitreous sample is drawn several hours after the first. What is the PRIMARY purpose of this approach?
- A To confirm that the laboratory assay was reproducible
- B To dilute cellular contaminants before analysis
- C To calculate the individual case-specific rate of potassium rise instead of relying on population averages ✓
- D To measure glucose accurately, which requires serial sampling
Correct answer: C. To calculate the individual case-specific rate of potassium rise instead of relying on population averages
Explanation
Population-based formulas such as Sturner assume a fixed average rate of potassium rise, producing confidence intervals of several hours. Drawing paired samples from both eyes at different times allows calculation of the actual slope of potassium increase in that specific body, substantially narrowing the interval estimate. The purpose is not assay quality control, dilution, or glucose measurement; glucose is not used in serial slope determination.
Reference: Knight's Forensic Pathology, 4th ed.
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