Vitreous and Postmortem Biochemistry for Time Since Death MCQs

Forensic Medicine · 17 free questions with answers & explanations.

1. Which vitreous humor biochemical marker is considered the MOST reliable for estimating time since death because it rises linearly and is least affected by decomposition?
2. A forensic pathologist notes the following vitreous biochemistry values from a decomposed body: Na+ 116 mEq/L, K+ 22 mEq/L, Cl- 90 mEq/L. The vitreous sodium:potassium ratio is approximately 5.3. What does a vitreous potassium of 22 mEq/L most likely suggest?
3. Postmortem vitreous hypoxanthine measurement is used as a supplement to vitreous potassium for TSD estimation. Hypoxanthine is a product of:
4. Vitreous potassium is used forensically to estimate postmortem interval (PMI). Which statement BEST describes the mechanism and reliability of this method?
5. A forensic pathologist finds vitreous glucose concentration of 0 mg/dL and elevated vitreous lactate in a body retrieved 24 hours after death. The most likely antemortem clinical context is:
6. In postmortem chemistry, the preferred specimen for estimating antemortem blood glucose and urea levels is vitreous humour rather than peripheral blood because:
7. Postmortem hypostasis (livor mortis) is described as 'non-shifting' after approximately 8–12 hours. Which biochemical process primarily accounts for this fixation?
8. Vitreous humor is preferred over serum for postmortem potassium estimation to determine time since death. The principal reason for this preference is:
9. Using the Henssge nomogram and Vitreous potassium method together, an investigator estimates postmortem interval (PMI) as 18–22 hours. The vitreous potassium is 11.2 mmol/L. Applying the formula PMI (hours) = 7.14 × [K+] – 39.1, calculate the estimated PMI:
10. Postmortem hypoxanthine levels in the vitreous humor are useful for estimating time since death because hypoxanthine:
11. A body found with a vitreous sodium of 138 mmol/L and vitreous chloride of 105 mmol/L, and serum sodium of 188 mmol/L is examined. The MOST likely explanation for this discrepancy is:
12. Vitreous humour potassium rises predictably after death due to leakage from retinal cells. At an ambient temperature of 20°C, the approximate rate of rise of vitreous potassium used in forensic TSD (time since death) estimation is:
13. A vitreous sample from a decomposed body shows glucose of 0 mg/dL, hypoxanthine of 350 µmol/L, and urea of 12 mmol/L. The MOST likely interpretation of the markedly elevated hypoxanthine is:
14. In a suspected diabetic coma death, which vitreous parameter is most RELIABLE for establishing ante-mortem hyperglycaemia, given that postmortem blood glucose is invariably unreliable?
15. Postmortem vitreous potassium rises predictably after death. A vitreous K+ of 14 mEq/L is measured. Using the Sturner-Gantner formula (PMI in hours = 7.14 × K+ − 39.1), what is the estimated postmortem interval?
16. Vitreous humor biochemistry is preferred over blood for postmortem glucose estimation in suspected hypoglycemic death. What is the primary reason?
17. In a suspected case of diabetic ketoacidosis as cause of death, which postmortem vitreous finding would BEST support this diagnosis?