Urea nitrogen, creatinine, and uric acid levels in postmortem serum, vitreous humor, and pericardial fluid

Relationship between N-terminal pro-brain natriuretic peptide concentration and heart-type fatty acid-binding protein in postmortem urine

The clinical use of N-terminal pro-brain natriuretic peptide (NT-proBNP) and blood concentrations of heart-type fatty acid-binding protein (HFABP) is well-established in diagnosing heart conditions. However, their applicability in forensics is controversial due to postmortem changes. NT-proBNP and HFABP are excreted in the urine due to their small molecular weights and may be found in postmortem urine samples; however, their correlation has not been evaluated. In this study, we compared the concentrations of urinary NT-proBNP and HFABP in 386 forensic autopsy cases. The urinary NT-proBNP levels were significantly higher in acute myocardial infarction (AMI), congestive heart failure (CHF), sepsis, and hyperthermia cases, with the highest levels in CHF cases. Similarly, HFABP concentration was significantly higher in CHF, sepsis, and hyperthermia cases, with the highest level observed in hyperthermia cases. However, the difference in urinary HFABP levels between the AMI and control cases was not significant. Our analysis revealed a correlation between postmortem urine NT-proBNP and HFABP levels, and the NT-proBNP/HFABP ratio was high in patients with CHF and sepsis cases and low in those with hyperthermia. The difference between the ratios was possibly due to the combined release of ventricular myocardial cells in response to ventricular wall stress and myocardial injury for NT-proBNP, as well as myocardial and skeletal muscle injuries for HFABP. This study, for the first time, demonstrates the utility of postmortem measurements of urinary NT-proBNP and HFABP levels, offering valuable insights for improving the accuracy of postmortem diagnosis in forensic medicine.

Objective evaluation of changes in serum transmittance over time using a portable color digitizer

Forensic pathologists empirically understand that postmortem changes can decrease serum transparency and change its color. Such changes are potential indicators for estimating postmortem intervals; however, reports on color changes focusing on postmortem changes in serum are scarce. To elucidate the effect of postmortem intervals on serum levels, we quantitatively evaluated and investigated the relationship between serum color and time using venous blood samples obtained from three healthy male volunteers. The serum samples were separated at 0 (1 h), 1, 2, 3, 4, 7, 10, 16, 21, and 28 days of storage. Serum transmittance and color were measured using a portable color digitizer and a custom-made measurement tool, respectively. Additionally, serum sodium (Na) and potassium (K) concentrations were measured. Serum transmittance showed a logistic curve-like decrease from 0.652 ± 0.016 (0 days) to 0.101 ± 0.014 (28 days) over time. The color changed from greenish yellow (dominant wavelength: 574.4 ± 0.63 nm) to reddish orange (603.97 ± 1.31 nm). Serum Na concentration decreased, whereas serum K concentration increased along the logistic curve. Strong (0.89, p < 0.001) and inverse correlations (-0.93, p < 0.001) were observed between the serum transmittance decrease and the Na concentration decrease and the K concentration increase, respectively. Serum transmittance decreased over time, indicating a transition from bright to dark. Moreover, a strong correlation was observed between serum transmittance and electrolytes, indicating a relationship between time course, serum transmittance, and electrolytes. These findings may contribute to the estimation of postmortem intervals in the future.

Postmortem Analysis of Vitreous Urea Nitrogen, Creatinine, and Magnesium of Renal and Post-Renal Disease in Cats

Analysis of vitreous urea nitrogen (VUN) and creatinine (CREA) has been shown to be a useful indicator of azotemia in human postmortem examinations. Previous studies in cats, dogs, horses, and cattle have shown a good correlation between serum and postmortem ocular fluid for urea and creatinine. The aim of this study was to evaluate differences in VUN, CREA, and magnesium (MG) concentrations in vitreous humor collected postmortem from cats that presented with renal or post-renal disease and cats without renal or post-renal disease. Nine cats with renal or post-renal disease and twenty cats without renal or post-renal disease that underwent autopsy were used in this study. Collection of postmortem vitreous humor was performed, and vitreous samples were frozen at -80 °C for a minimum of 24 h prior to analysis using an in-clinic dry chemistry analyzer. Overall, there were statistically significant differences for VUN, CREA, and MG between cats with renal or post-renal disease and cats without renal or post-renal disease. Analysis of vitreous humor from cats suspected to have renal or post-renal disease can provide useful diagnostic information pertaining to renal function and issues in the urethra and urinary bladder. Future studies exploring postmortem vitreous chemistry in cats are warranted.

Postmortem reference concentrations of 68 elements in blood and urine

INTRODUCTION

Fatal intoxications, both accidental and intentional, are a global issue. In the Western world, intoxications with pharmaceuticals dominate, but in other parts of the world, other substances are more common. In a forensic setting, elemental intoxications are of great importance when investigating both accidental, suicidal, and homicidal deaths. The current study presents normal postmortem reference concentrations of 68 elements in femoral blood and urine. In addition, possible sources of error such as contamination from sample tubes, preservative potassium fluoride (KF) solution, and storage time are evaluated.

METHODS

Paired femoral blood and urine samples from 120 cases of death by suicidal hanging in Sweden were collected. Additionally, multiple batches of sample tubes and multiple batches of KF solution were also analyzed. Concentrations of elements were determined by double focusing sector field ICP-MS.

RESULTS

Key descriptive statistics for 68 elements are provided in blood and urine. Contamination from sample tubes was minor compared to the overall mean elemental concentrations in both blood and urine. KF solution contained a large assortment of elements, but the overall contribution is relatively minor for most elements given the small amounts of solution added to samples. There were significant differences for 22 elements in blood and 17 elements in urine between samples with short and long storage time.

CONCLUSION

The present study provides an important tool when evaluating postmortem elemental concentrations. It fills a needed gap between large antemortem population studies and postmortem case reports or small case series of elemental intoxications.

Osmotic gradients and transretinal water flow-a quantitative elemental microanalytical study of frozen hydrated chick eyes

Optical clarity and efficient phototransduction are necessary for optimal vision, however, how the associated processes of osmoregulation and continuous fluid drainage across the whole eye are achieved remains relatively unexplored. Hence, we have employed elemental microanalysis of planed surfaces of light-adapted bulk frozen-hydrated chick eyes to determine the unique intracellular elemental localization, compositions, and hydration states that contribute to maintaining osmotic gradients and water flow from the vitreous, across the retina, retinal pigment epithelium (RPE), to choroid and sclera. As expected, the greatest difference in resultant osmotic concentration gradients, [calculated using the combined concentrations of sodium (Na) and potassium (K)] and tissue hydration [oxygen-defined water concentration], occurs in the outer retina and, in particular, in the RPE where the apical and basal membranes are characterized by numerous bioenergetically active, osmoregulating ion transport mechanisms, aquaporins, and chloride (Cl) channels. Our results also demonstrate that the high intracellular Na+ and K+ concentrations in the apical region of the RPE are partially derived from the melanosomes. The inclusion of the ubiquitous osmolyte taurine to the calculation of the osmotic gradients suggests a more gradual increase in the osmotic transport of water from the vitreous into the ganglion cell layer across the inner retina to the outer segments of the photoreceptor/apical RPE region where the water gradient increases rapidly towards the basal membrane. Thus transretinal water is likely to cross the apical membrane from the retina into the RPE cells down the Na+ and K+ derived osmotic concentration gradient and leave the RPE for the choroid across the basal membrane down the Cl- derived osmotic concentration gradient that is sustained by the well-described bioenergetically active RPE ion transporters and channels.

Accuracy of Urea Nitrogen and Creatinine Measurements in Postmortem Serum and Pericardial Fluid Compared With Antemortem Data

ABSTRACT

Although several studies have measured urea nitrogen (UN) and creatinine (Cr) concentrations in postmortem serum and pericardial fluid, no recent antemortem biochemical data have been available for forensic autopsy, thereby making the evaluation of the accuracy of postmortem data difficult. This study compared antemortem (from emergency room results before the declaration of death) and postmortem serum UN and Cr concentrations, as well as postmortem serum and pericardial fluid values, in 51 forensic autopsy cases (postmortem interval within 87 hours). Postmortem UN concentrations were strongly correlated with antemortem data. Moreover, no significant difference between pericardial fluid UN concentrations and antemortem data was observed. Postmortem serum and pericardial fluid Cr values were also correlated with antemortem data, although postmortem values were significantly higher than antemortem ones. Given our observation of early postmortem elevation in Cr concentrations, such an elevation was attributed to rigor mortis. In conclusion, the current study demonstrated the utility of postmortem UN and Cr concentrations, in particular of those measured in the pericardial fluid.

Disease network delineates the disease progression profile of cardiovascular diseases

OBJECTIVE

As Electronic Health Records (EHR) data accumulated explosively in recent years, the tremendous amount of patient clinical data provided opportunities to discover real world evidence. In this study, a graphical disease network, named progressive cardiovascular disease network (progCDN), was built to delineate the progression profiles of cardiovascular diseases (CVD).

MATERIALS AND METHODS

The EHR data of 14.3 million patients with CVD diagnoses were collected for building disease network and further analysis. We applied a new designed method, progression rates (PR), to calculate the progression relationship among different diagnoses. Based on the disease network outcome, 23 disease progression pair were selected to screen for salient features.

RESULTS

The network depicted the dominant diseases in CVD development, such as the heart failure and coronary arteriosclerosis. Novel progression relationships were also discovered, such as the progression path from long QT syndrome to major depression. In addition, three age-group progCDNs identified a series of age-associated disease progression paths and important successor diseases with age bias. Furthermore, a list of important features with sufficient abundance and high correlation was extracted for building disease risk models.

DISCUSSION

The PR method designed for identifying the progression relationship could be widely applied in any EHR database due to its flexibility and robust functionality. Meanwhile, researchers could use the progCDN network to validate or explore novel disease relationships in real world data.

CONCLUSION

The first-time interrogation of such a huge CVD patients cohort enabled us to explore the general and age-specific disease progression patterns in CVD development.

Post-mortem changes in metabolomic profiles of human serum, aqueous humor and vitreous humor

INTRODUCTION

Application of metabolomic methods to forensic studies may expand the limits of the post-mortem interval (PMI) estimation, and improve the accuracy of the estimation. To this end, it is important to determine which tissue is the most suitable for analysis, and which compounds are the most promising candidates for PMI estimation.

OBJECTIVES

This work is aimed at the comparison of human serum, aqueous humor (AH), and vitreous humor (VH) as perspective tissues for metabolomic-based PMI estimation, at the determination of most promising PMI biomarkers, and at the development of method of PMI estimation based on the measurement of concentrations of PMI biomarkers.

METHODS

Quantitative metabolomic profiling of samples of the human serum, AH, and VH taken at different PMIs has been performed with the use of NMR spectroscopy.

RESULTS

It is found that the metabolomic changes in anatomically isolated ocular fluids are slower and smoother than that in blood. A good positive time correlation (Pearson coefficient r > 0.5) was observed for several metabolites, including hypoxanthine, choline, creatine, betaine, glutamate, and glycine. A model for PMI estimation based on concentrations of several metabolites in AH and VH is proposed.

CONCLUSIONS

The obtained results demonstrate that the metabolomic analysis of AH and VH is more suitable for the PMI estimation than that of serum. The compounds with good positive time correlation can be considered as potential PMI biomarkers.

Improvement in estimation of time since death by albumin and potassium concentrations in vitreous humor

The measurement of the potassium concentration (K⁺) in vitreous humor (VH) has been a well-known adjunct for the estimation of the post-mortem interval (PMI) since the early 1960s. For years, however, many authors have been using other biochemical markers in an attempt to improve predictions. In this paper we confirm the role of K⁺ in the determination of the PMI adopting a linear regression model and we investigate whether other biochemical markers could improve the model through a multiple regression analysis. Additionally, the research aims to confirm the data of the analytes of interest among different techniques and instrumentations. We deemed this as an important issue because a primary concern in the literature is that automated analytical methods are often calibrated and, for the most part, validated for serum or urine analysis. Our results confirmed the well-established role of K⁺ as well as highlighted Albumin as a novel marker to be considered for further improvement of prediction models, especially since 72 h after death.

The Estimation of Postmortem Serum Urea via the Ultrafiltration of Hemolyzed Blood

Postmortem serum urea has been demonstrated as an objective indicator for the forensic diagnosis of cause of death. However, samples used in postmortem biochemical analysis are always affected by hemolysis. To investigate whether hemolysis affects the biochemical analysis of urea and to explore the feasibility of using ultrafiltration to process hemolyzed blood samples, three different levels of hemolyzed blood samples were used to assess the influence of hemolysis on postmortem biochemical analysis of urea, and two ultrafiltration methods were used to process the hemolyzed blood samples. Bias% was used to assess the interference of hemolysis. Our results showed that heavy hemolysis had a significant influence on the biochemical analysis of urea. Both ultrafiltration methods in the present study could significantly reduce the interference of hemolysis, with the |bias%| of methods A and B decreasing from 69.74% ± 99.14% to 12.18% ± 7.23% and 10.77% ± 8.09%, respectively, compared to the original serum. After regression correction, there was no significant difference between the urea concentration in the ultrafiltrates of the two ultrafiltration methods and that in the original serum, which suggested that the postmortem serum urea concentration could be estimated by the corrected urea concentration in the ultrafiltrate. The current study also provided possible pretreatment methods for postmortem biochemical analysis of other biomarkers in hemolyzed blood samples of forensic practice.

Vitreous humor endogenous compounds analysis for post-mortem forensic investigation

The chemical and biochemical analysis of bodily fluids after death is an important thanatochemical approach to assess the cause and time since death. Vitreous humor (VH) has been used as a biofluid for forensic purposes since the 1960s. Due to its established relevance in toxicology, a literature review highlighting the use of VH with an emphasis on endogenous compounds has not yet been undertaken. VH is a chemically complex aqueous solution of carbohydrates, proteins, electrolytes and other small molecules present in living organisms; this biofluid is useful tool for its isolated environment, preserved from bacterial contamination, decomposition, autolysis, and metabolic reactions. The post-mortem analysis of VH provides an important tool for the estimation of the post-mortem interval (PMI), which can be helpful in determining the cause of death. Consequently, the present review evaluates the recent chemical and biochemical advances with particular importance on the endogenous compounds present at the time of death and their modification over time, which are valuable for the PMI prediction and to identify the cause of death.

Feasibility Study of MRI Muscles Molecular Imaging in Evaluation of Early Post-Mortem Interval

Estimating early postmortem interval (EPI) is a difficult task in daily forensic activity due to limitations of accurate and reliable methods. The aim of the present work is to describe a novel approach in the estimation of EPI based on quantitative magnetic resonance molecular imaging (qMRMI) using a pig phantom since post-mortem degradation of pig meat is similar to that of human muscles. On a pig phantom maintained at 20° degree, using a 1.5 T MRI scanner we performed 10 scans (every 4 hours) monitoring apparent diffusion coefficient (ADC), fractional anisotropy (FA) magnetization transfer ration (MTR), tractography and susceptibility weighted changes in muscles until 36 hours after death. Cooling of the phantom during the experiment was recorded. Histology was also obtained. Pearson’s Test was carried out for time correlation between post-mortem interval and MRI data. We found a significative inverse correlation between ADC, FA, MT values and PMI. Our preliminary data shows that post-mortem qMRMI is a potential powerful tool in accurately determining EPI and is worth of further investigation.

Post-mortem interval estimative through determination of catalase and Δ-aminolevulinate dehydratase activities in hepatic, renal, skeletal muscle and cerebral tissues of Swiss mice

Purpose: Determining the post-mortem interval (PMI) is one of the challenging tasks in forensic science due to the lack of quick and inexpensive methods. Our objective is to develop innovative and alternative means for PMI evaluation. Methods: The relationship between PMI and enzymatic modifications in mice tissues was described. After being sacrificed, Swiss mice were randomly divided into groups according to the time elapsed since death. The activities of catalase (CAT) and δ-aminolevulinate dehydratase (δ-ALA-D) were determined in hepatic, renal, skeletal muscle and cerebral tissues. Results: CAT activity increased in kidney and brain 6 h after death and this increase remained for up to 24 h in the brain and 48 h in the kidney. δ-ALA-D had its activity decreased in the liver and kidneys in 6 h. In the skeletal muscle, δ-ALA-D activity was reduced only 48 h after death. Conversely, an increase on δ-ALA-D activity was observed in the brain at 6 h, followed by its decrease at 24 and 48 h. Conclusion: With the association of this set of results, it is possible to provide an estimate of PMI. Additionally, these results can be used as an auxiliary parameter associated with other methods to estimate PMI.

A 1H NMR metabolomic approach for the estimation of the time since death using aqueous humour: an animal model

INTRODUCTION

The estimation of the time since death, or post-mortem interval (PMI), still remains a main conundrum in forensic science. Several approaches have been so far proposed from either a qualitative or a quantitative point of view, but they still lack reliability and robustness. Recently, metabolomics has shown to be a potential tool to investigate the time-related post-mortem metabolite modifications in animal models.

OBJECTIVES

Here we propose, for the first time, the use of a ¹H NMR metabolomic approach for the estimation of PMI from aqueous humour (AH) in an ovine model.

METHODS

AH samples were collected at different times after death (from 118 to 1429 min). ¹H NMR experiments were performed and spectral data analysed by multivariate statistical tools.

RESULTS

A multivariate calibration model was built to estimate PMI on the basis of the metabolite content of the samples. The model was validated with an independent test set, obtaining a prediction error of 59 min for PMI < 500 min, 104 min for PMI from 500 to 1000 min, and 118 min for PMI > 1000 min. Moreover, the metabolomic approach suggested a picture of the mechanisms underlying the post-mortem biological modifications, highlighting the role played by taurine, choline, and succinate.

CONCLUSION

The time-related modifications of the ¹H NMR AH metabolomic profile seem to be encouraging in addressing the issue of a reproducible and robust model to be employed for the estimation of the time since death.

Evaluating the effects of causes of death on postmortem interval estimation by ATR-FTIR spectroscopy

Estimating postmortem interval (PMI) is one of the most challenging tasks in forensic practice due to the effects of many factors. Here, attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy combined with chemometrics was utilized to evaluate the effects of causes of death when estimating PMI and to establish a partial least square (PLS) regression model, which can precisely predict PMI under different causes of death. First, the sensitivities to causes of death (brainstem injury, mechanical asphyxia, and hemorrhage shock) of seven kinds of organs were evaluated based on their degrees of cohesion and separation. Then, the liver was selected as the most sensitive organ to establish a PMI estimation model to compare the predicted deviations from different causes of death. It turns out that the cause of death has no significant effect on estimating PMI. Next, a PLS regression model was built with kidney tissues, which have the lowest sensitivity, and this model showed a satisfactory predictive ability and wide applicability. This study demonstrates the feasibility of using ATR-FTIR spectroscopy in conjunction with chemometrics as a powerful alternative for detecting changes in biochemistry and estimating PMI. A new perspective was also provided for evaluating the effect of causes of death when predicting PMI.

Quantitative metabolomic analysis of changes in the lens and aqueous humor under development of age-related nuclear cataract

INTRODUCTION

Metabolites are essential for the proper functioning of the eye lens, they either enter the lens from the aqueous humor (AH), or are synthesized in the lens epithelium. Antioxidants, osmolytes and UV filters are especially important for the lens protection, and their lack may cause the development of ophthalmic diseases.

OBJECTIVES

Comparison of the metabolomic compositions of lenses and AH taken from cataract patients with that taken from human cadavers without cataract can shed light onto molecular mechanisms underlying onset of age-related nuclear cataract.

METHODS

Combined use of ¹H nuclear magnetic resonance and high performance liquid chromatography with optical and high-resolution mass spectrometric detection for the identification and quantification of metabolites in the lens and AH extracts.

RESULTS

The concentrations of 86 metabolites were determined for four groups of samples, including lenses and AH from cataract patients and from human cadavers. In cataractous lens the most abundant metabolites are (in descending order): myo-inositol, lactate, acetate, glutamate, glutathione; in AH-lactate, glucose, glutamine, alanine, valine. The concentrations of the majority of metabolites in normal post-mortem samples of both lens and AH are higher than that in samples from the cataract patients.

CONCLUSIONS

Comparison of metabolite concentrations in lens and corresponding AH reveal that the most important for the lens protection metabolites are synthesized in the lens epithelial cells. The reduced levels of antioxidants, UV filters, and osmolytes were found in the cataractous lenses what cannot be explained by post-mortem changes in normal lens; that indicates that the age-related nuclear cataract development may originate from the dysfunction of the lens epithelial cells.

Intra-individual alterations of serum markers routinely used in forensic pathology depending on increasing post-mortem interval

Post-mortem biochemistry of serum markers has been the subject of numerous studies, but in-situ marker stability after death has not been sufficiently evaluated yet. Such laboratory analyses are especially necessary in the cases of functional deaths without morphological evidence of the death causes and also in cardiac death cases with only very short survival times. The aim of the study was to determine the post-mortem stability of commonly-used serum markers at predefined time points. In 20 cases, peripheral venous samples were taken starting immediately after circulatory arrest and ending 48 hours after death. Serum creatinine, urea, 3-β-hydroxybutyrate, tryptase, myoglobin, troponin T, creatin kinase and creatin kinase-MB have been included. For all markers, we observed increasing marker levels for longer post-mortem intervals. Significant marker level changes began two hours after death. Excessive increases were observed for cardiac and muscle markers. Marker levels showed high intra-assay precision. Furthermore, the markers were robust enough to withstand freeze-thaw cycles. Potential contamination of arteriovenous blood did not influence the post-mortem marker levels. Post-mortem blood should be sampled as soon as possible, as increased post-mortem intervals may heavily change marker levels in-situ in individual cases, whereas the markers are mostly unaffected by laboratory conditions.

Pericardial fluid is suitable as an alternative specimen for the measurement of β-hydroxybutyrate within 96 h after death

We examined postmortem β-hydroxybutyrate (BHB) levels in the body fluids obtained from 253 forensic autopsy cases whose causes of death were determined. Postmortem changes of BHB levels according to postmortem intervals (PMI) in various body fluids (plasma, urine, vitreous humor, and pericardial fluids) were investigated to determine appropriate alternative specimens as plasma samples. Our study has indicated the following points: 1) the BHB levels in plasma specimens from three sampling sites showed no significant differences, 2) postmortem changes of BHB levels in plasma and pericardial fluids could be negligible within 96 h PMI, while urine and vitreous humor BHB levels showed postmortem changes, and 3) pericardial fluid would thus be most suitable as an alternative to plasma in postmortem BHB level. We have also proposed that BHB levels could be applicable for the diagnosis of metabolic disorders in forensic autopsy.

MALDI-TOF MS as a Novel Tool for the Estimation of Postmortem Interval in Liver Tissue Samples

Estimation of the postmortem interval (PMI) is a complicated task in forensic medicine, especially during homicide and unwitnessed death investigations. Many biological, chemical, and physical indicators can be used to determine the postmortem interval, but most are not accurate. Here, we present a novel matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) method that can be used for the estimation of PMI using molecular images and multivariate analyses. In this study, we demonstrate that both rat and human liver tissues of various PMIs (0, 2, 4, and 6days) can be discriminated using MALDI imaging and principal component analysis (PCA). Using genetic algorithm (GA), supervised neural network (SNN), and quick classifier (QC) methods, we built 6 classification models, which showed high recognition capability and good cross-validation. The histological changes in all the samples at different time points were also consistent with the changes seen in MALDI imaging. Our work suggests that MALDI-TOF MS, along with multivariate analysis, can be used to determine intermediate PMIs.

Characterization of postmortem biochemical changes in rabbit plasma using ATR-FTIR combined with chemometrics: A preliminary study

Postmortem interval (PMI) determination is one of the most challenging tasks in forensic medicine due to a lack of accurate and reliable methods. It is especially difficult for late PMI determination. Although many attempts with various types of body fluids based on chemical methods have been made to solve this problem, few investigations are focused on blood samples. In this study, we employed an attenuated total reflection (ATR)-Fourier transform infrared (FTIR) technique coupled with principle component analysis (PCA) to monitor biochemical changes in rabbit plasma with increasing PMI. Partial least square (PLS) model was used based on the spectral data for PMI prediction in an independent sample set. Our results revealed that postmortem chemical changes in compositions of the plasma were time-dependent, and various components including proteins, lipids and nucleic acids contributed to the discrimination of the samples at different time points. A satisfactory prediction within 48h postmortem was performed by the combined PLS model with a good fitting between actual and predicted PMI of 0.984 and with an error of ±1.92h. In consideration of the simplicity and portability of ATR-FTIR, our preliminary study provides an experimental and theoretical basis for application of this technique in forensic practice.

Research progress in the estimation of the postmortem interval by Chinese forensic scholars

The determination of time since death or the postmortem interval (PMI) is one of the most important and frequently asked questions in forensic medicine. Medicolegal scholars and forensic pathologists around the world have studied the estimation of PMI extensively in the past, and many novel methods and advanced technologies have now been applied in the field. For several centuries, Chinese forensic examiners have also worked on the estimation of the PMI, and there are a large number of excellent studies published in Chinese rather than in English, and these are not easily accessible or known internationally. Therefore we have conducted a review of relevant studies published by Chinese forensic scholars in the last few decades. The scope of this review is to provide a concise summary of the current progress in the estimation of PMI by Chinese forensic researchers using molecular biology, spectroscopic technology, entomological methods, energy changes, thanatochemistry and other methods.

Postmortem biochemistry: Current applications

The results of biochemical analyses in specimens obtained postmortem may aid death investigation when diabetic and alcoholic ketoacidosis is suspected, when death may have been the result of drowning, anaphylaxis, or involved a prolonged stress response such as hypothermia, and in the diagnosis of disease processes such as inflammation, early myocardial infarction, or sepsis. There is often cross-over with different disciplines, in particular with clinical and forensic toxicology, since some endogenous substances such as sodium chloride, potassium chloride, and insulin can be used as poisons. The interpretation of results is often complicated because of the likelihood of postmortem change in analyte concentration or activity, and proper interpretation must take into account all the available evidence. The unpredictability of postmortem changes means that use of biochemical measurements in time of death estimation has little value. The use of vitreous humour is beneficial for many analytes as the eye is in a physically protected environment, this medium may be less affected by autolysis or microbial metabolism than blood, and the assays can be performed with due precaution using standard clinical chemistry analysers. However, interpretation of results may not be straightforward because (i) defined reference ranges in life are often lacking, (ii) there is a dearth of knowledge regarding, for example, the speed of equilibration of many analytes between blood, vitreous humour, and other fluids that may be sampled, and (iii) the effects of post-mortem change are difficult to quantify because of the lack of control data. A major limitation is that postmortem vitreous glucose measurements are of no help in diagnosing antemortem hypoglycaemia.

Renal markers cystatin C and neutrophil gelatinase-associated lipocalin (NGAL) in postmortem samples

PURPOSE

Renal markers may provide valuable information for cause of death (CoD) investigation when assessing the influence of impaired kidney function. A commonly used marker, creatinine (Cr), increases due to kidney injury and is known to be reasonably stable in postmortem (PM) samples. More sensitive markers are needed, as the increase of serum Cr level only occurs after relatively severe renal damage. We evaluated two markers, cystatin C and neutrophil gelatinase-associated lipocalin (NGAL), in addition to Cr. To the best of our knowledge this was the first study to investigate cystatin C and NGAL in a postmortem (PM) context.

METHODS

Cr, cystatin C, and NGAL were measured from PM blood in 39 autopsy cases. NGAL was also measured from urine in 16 cases. Cystatin C and NGAL were analyzed using ELISA, Cr measurements were performed with Jaffe method. Correlations of these markers were evaluated.

RESULTS AND CONCLUSIONS

Both, blood cystatin C and NGAL, levels showed significant correlation with Cr (p = 0.05 and p = 0.01, respectively). Cystatin C and NGAL in blood are promising markers for further studies with PM samples.

Response to the comment on "Promising blood-derived biomarkers for estimation of the postmortem interval"

Following Meurs and Szykuła's comment on our published article titled "Promising blood-derived biomarkers for estimation of the postmortem interval", we recognize the importance of the issues raised, but we would like to emphasize that these contain some misinterpretations and that most of the points were already discussed in depth in our manuscript particularly in the conclusion section. We also aim to highlight further data regarding the difficulties of postmortem interval estimation.

Comment on "Promising blood-derived biomarkers for estimation of the postmortem interval" by I. Costa, F. Carvalho, T. Magalhães, P. G. de Pinho, R. Silvestre & R. J. Dinis-Oliveira. (Toxicol. Res., 2015, , 1443-1452)

Recently, Costa et al. published an article about promising biomarkers for estimating the postmortem interval. Instead of postmortem blood, antemortem blood was putrefied in vitro by exposing the blood to a temperature gradient. However, in this way several other influencing factors were excluded, hence, the accuracy of the proposed model is doubtful. Therefore, the aim of this comment is to discuss the methodology, results and shortcomings of the study of Costa et al.

Postmortem diagnosis of diabetes mellitus and its complications

Diabetes mellitus has become a major cause of death worldwide and diabetic ketoacidosis is the most common cause of death in children and adolescents with type 1 diabetes. Acute complications of diabetes mellitus as causes of death may be difficult to diagnose due to missing characteristic macroscopic and microscopic findings. Biochemical analyses, including vitreous glucose, blood (or alternative specimen) beta-hydroxybutyrate, and blood glycated hemoglobin determination, may complement postmortem investigations and provide useful information for determining the cause of death even in corpses with advanced decompositional changes. In this article, we performed a review of the literature pertaining to the diagnostic performance of classical and novel biochemical parameters that may be used in the forensic casework to identify disorders in glucose metabolism. We also present a review focusing on the usefulness of traditional and alternative specimens that can be sampled and subsequently analyzed to diagnose acute complications of diabetes mellitus as causes of death.