ORIGINAL ARTICLE Year : 2016  Volume : 7  Issue : 2  Page : 9699 Vitreous potassium concentration as a predictor of postmortem interval: A crosssectional study among natural death cases at a tertiary care center in rural Haryana Rajesh Duraisamy Rathinam^{1}, Abhishek Singh^{2}, Karkala Jayaprakash^{3}, Pooja Goyal^{4}, Pankaj Chikkara^{5}, Sanjeev Kumar Khichi^{2}, Shwetank Goel^{6}, ^{1} Department of Forensic Medicine, Indira Gandhi Medical College and Research Institute, Puducherry, India ^{2} Department of Community Medicine, Shaheed Hasan Khan Mewati Government Medical College, Nalhar, India ^{3} Department of Forensic Medicine, AJ Institute of Medical Sciences, Mangalore, Karnataka, India ^{4} Department of Community Medicine, ESIC Medical College, Faridabad, India ^{5} Department of Forensic Medicine, Post Graduate Institute of Medical Sciences, Rohtak, Haryana, India ^{6} Department of Microbiology, Teerthanker Mahaveer Medical College and Research Centre, Moradabad, Uttar Pradesh, India Correspondence Address: Background: Time since death (TSD) is an important parameter to the forensic expert. Only a few studies are available in the literature to determine the relationship between the vitreous potassium (K ^{+} ) concentration and TSD especially among natural death cases in the state of Haryana and, thus, information on the same is patchy and scanty. Objective: To determine the relationship between changes in the vitreous K ^{+} concentration and increasing TSD among natural death cases. An additional objective was to derive a formula for determining TSD from changes in levels of vitreous K ^{+} in the study subjects. Materials and Methods: In this study, autopsy cases brought to the mortuary of the Department of Forensic Medicine and Toxicology of a tertiary care center, were the subjects for collection of vitreous humor for the determination of vitreous K ^{+} . Data of 90 such cases where autopsy confirmed the cause of death as natural death were included in this study. Determination of K ^{+} level in the collected sample was done by ionselective electrode method (Biolyte 2000 autoanalyzer, Biocare, Lujhu Township, Taiwan). Results: A linear relationship was observed between vitreous K ^{+} concentration and TSD in both the eyes. External factors like seasonal variations and temperature, gender difference, and age had no appreciable effect on the concentration of vitreous K ^{+} in either eye. In this study, the linear regression equations obtained from K ^{+} concentration (y) versus time (x) for the two groups among injury (trauma) cases were as follows: For the right eye: Regression line (y) = 4.303 x + 2.148 and for the left eye: Regression line (y) = 5.260 x + 2.209. The K ^{+} levels are found to increase up to 40 h after death. Conclusion: The study highlighted the usefulness of the relationship between vitreous K ^{+} concentration and TSD in both the eyes. The formula calculated from the current study could prove to be more appropriate as it is based on a more recent study and more reliable tests.
Introduction Time since death (TSD) is an important parameter to the forensic expert and also to the investigating agency if determined with measurable accuracy. TSD is an important question asked to every forensic expert appearing in court for evidence. [1] But determination of accurate TSD is extremely difficult as timings of the onset and the rates of postmortem changes are usually governed by unpredictable endogenous and exogenous factors. [2] Due to its postmortem stability, vitreous humor has high utility in forensic pathology. The biochemical constituents of vitreous humor, especially potassium (K + ), have been widely used in the postmortem interval estimations. The time dependent rise of vitreous K + levels in the postmortem period has been considered to be helpful in postmortem interval determination. [3] Only a few studies are available in the literature to determine the relationship between vitreous K + concentration and TSD especially among natural death cases in the state of Haryana and, thus, the information on the same is patchy and scanty. Therefore, the present study was planned to determine the relationship between the changes in vitreous K + concentration and increasing TSD among natural death cases in Haryana. An additional objective was to derive a formula for determining TSD from changes in the levels of vitreous K + in the study subjects. Materials and Methods In this crosssectional study, autopsy cases brought to the mortuary of the Department of Forensic Medicine and Toxicology of a tertiary care center were the subjects for collection of vitreous humor for determination of vitreous K + . Data of 90 such cases where autopsy confirmed the cause of death as natural death were included in this study. Vitreous humor was collected at the time of autopsy examination. Most of the vitreous humor K + analyses were carried out immediately postextraction on the same day of collection. The information regarding time of death was gathered from police records, hospital records, or from eye witnesses, relatives, friends, and attendants of the deceased. The TSD, thus, obtained was further crossverified by postmortem changes like hypostasis, rigor mortis, and putrefaction. The data were collected in three groups according to TSD from 0 h to 12 h, 12.01 h to 24 h, and above 24 h, respectively, recorded on proforma. Cases with known or suspected ocular diseases, trauma to head, vitreous fluid cloudy or contaminated with blood, vitreous humor insufficient for the biochemical analyses, and those cases whose time of death on enquiry from different sources was found to differ by more than ±15 min, were excluded from the study. Determination of K + level in the collected sample was done by ionselective electrode method (Biolyte 2000 autoanalyzer, Biocare, Lujhu Township, Taiwan). The collected data were coded and entered in Statistical Package for Social Sciences (SPSS), version 17. Interpretation of the collected data was done by using appropriate statistical methods and tests like chisquare test. Two tailed P < 0.05 was considered statistically significant. Correlation among variables and regression equation were also derived. Results Data of 90 study subjects belonging to natural death cases were analyzed in the present study. The mean level of K + in the right eye was found to be 9.3 ± 2.40 mEq/L (range 4.5010.20). On the other hand the mean level of K + in the left eye was found to be 9.5 ± 2.40 mEq/L (range 4.5010.20). This difference in the rise of K+ level between right and left eyes was found to be nonsignificant statistically [Table 1].{Table 1} There is an evident rise in the K + concentration with the increasing TSD in both the right and left eyes. This pattern was observed in all the three groups of TSD, i.e., within 12 h, upto 24 h,and more than 24 h. The difference in K + concentration levels among all the three TSD groups between right and left eyes was found to be highly significant statistically [Table 2].{Table 2} Effect of external factors, gender, and age on the concentration of vitreous potassium It was observed in this study that external factors like seasonal variations and temperature, gender difference, and age had no appreciable effect on the concentration of vitreous K + in either eye. Following values and linear regression equation obtained from K + concentration (y) versus time (x) derived from [Table 3] for the right eye were as follows: Pearson's correlation Coefficient (r) = + 0.867 Coefficient of determination (r2) = 0.752 Coefficient of regression equation (R) = 0.867 Regression line (y) = −4.303 x + 2.148 From these above values, the least square regression line is drawn on [Figure 1]. {Figure 1}{Table 3} 95% confidence limit of x = Mean ± 2SD of x 0 = Mean ± 11.98 Regression Coefficient = r SD of x χ SD of y This means that an increase of K + values of 1 mEq/L will indicate an increase of 2.14 h in the postmortem interval and 95% confidence limit for all cases will be ±11.98 h. Following values and linear regression equation obtained from K + concentration (y) versus time (x) derived from [Table 3] for the left eye were as follows: Pearson's correlation Coefficient (r) = + 0.888 Coefficient of determination (r2) = 0.788 Coefficient of regression equation (R) = 0.888 Regression line (y) = −5.260 x + 2.209 From these above values, the least square regression line is drawn on [Figure 2].{Figure 2} 95% confidence limit of x = Mean ± 2SD of x = Mean ± 11.98 Regression Coefficient = r SD of x χ SD of y This means that an increase of K + values of 1 mEq/L will indicate an increase of 2.21 h in the postmortem interval and 95% confidence limit for all cases will be ±11.98 h. Discussion The findings of our study show that with the increase of TSD, the level of K + in the vitreous humor goes on increasing. Prasad et al. [4] studied correlation of K + level of vitreous and the postmortem interval and found that the rise in K + level after death has a strong correlation with the postmortem interval. Mulla [5] hypothesized that the concentration of vitreous biochemical constituents in the same pair of eyes change at the same rate and this change that occurs in a time dependent fashion may be utilized in accurately estimating the postmortem interval. Regarding the role of age in the changes of K + concentration levels in the vitreous humor after death, it was observed in this study that age has no appreciable role in the changes in the levels of K + concentration in the vitreous humor after death. This observation is consistent with the results of other study by Jashnani et al. [6] It was observed in this study that there was no effect of temperature on the levels of K + concentration in the vitreous humor after death. Another study by Ahi and Garg [7] is also in concordance with our observations. However, Farmer et al. [8] observed that in warm seasons with higher environmental temperature at the time of death caused marked enhancement of the observed K + values in the vitreous humor. This study contradicts the observations on this aspect of the study. In this study the linear regression equations obtained from K + concentration (y) versus time (x) for the two groups among natural death cases were as follows: For the right eye: Regression line (y) = 4.303 x + 2.148 and for left eye: Regression line (y) = 5.260 x + 2.209. In both study groups, a straight line relationship is found between the vitreous K + levels and the postmortem interval, which is in confirmation with the observation of made in most of the previous researches. [9],[10],[11],[12] The 95% confidence limit of over ±17 limits the usefulness of this method in predicting postmortem interval (95% confidence limits for our study subjects were ±13.78). Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest. References


