Application of Mixed-effect Model in PMI Estimation by Vitreous Humor
10.3969/j.issn.1004-5619.2018.01.003
- VernacularTitle:混合效应模型在玻璃体液推断死亡时间中的应用
- Author:
Ming-Zhen YANG
1
;
Hui-Jun LI
;
Tian-Ye ZHANG
;
Zi-Jiao DING
;
Shi-Fan WU
;
Xin-Gang QIU
;
Qian LIU
Author Information
1. 华中科技大学同济医学院法医学系
- Keywords:
forensic pathology;
vitreous body;
postmortem interval;
body fluids;
mixed-effect model;
potassium;
magnesium
- From:
Journal of Forensic Medicine
2018;34(1):13-17
- CountryChina
- Language:Chinese
-
Abstract:
Objective To test the changes of the potassium(K+)and magnesium(Mg2+)concentrations in vitreous humor of rabbits along with postmortem interval(PMI)under different temperatures, and explore the feasibility of PMI estimation using mixed-effect model. Methods After sacrifice, rabbit carcasses were preserved at 5℃, 15℃, 25℃ and 35℃, and 80-100μL of vitreous humor was collected by the double-eye alternating micro-sampling method at every 12 h. The concentrations of K+and Mg2+in vitreous humor were measured by a biochemical-immune analyser. The mixed-effect model was used to perform analy-sis and fitting, and established the equations for PMI estimation. The data detected from the samples that were stoned at 10℃, 20℃ and 30℃ with 20, 40 and 65 h were used to validate the equations of PMI estimation. Results The concentrations of K+and Mg2+[f(x,y)] in vitreous humor of rabbits under different temperature increased along with PMI(x). The relative equations of K+and Mg2+concentration with PMI and temperature under 5℃~35℃ were fK+(x,y)=3.413 0+0.309 2 x+0.337 6 y+0.010 83 xy-0.002 47 x2 (P<0.000 1), and fMg2+(x,y)=0.745 6+0.006 432 x+0.033 8 y(P<0.000 1), respectively. It was proved that the time of deviation for PMI estimation by K+and Mg2+was in 10 h when PMI was between 0 to 40 h, and the time of deviation was in 21 h when PMI was between 40 to 65 h. Conclusion In the ambient temperature range of 5℃-35℃, the mixed-effect model based on temperature and vitreous humor sub-stance concentrations can provide a new method for the practical application of vitreous humor chemi-cals for PMI estimation.
