The biochemistry of the vitreous humour in estimating the post-mortem interval-a review of the literature, and use in forensic practice in Galicia (northwestern Spain).

The K+ and hypoxanthine (Hx) concentrations of the vitreous humour (VH) rise gradually after death, providing a means of estimating the post-mortem interval (PMI). The correlation between these analytes and the PMI is good since the vitreous chamber is partially isolated from autolytic events occurring elsewhere; the [K +] and [Hx] recorded is thus the result of changes within the eye. The present work provides a systematic review, following PRISMA recommendations, of 36 articles (3 reviews and 33 retrospective cohort studies) discussing the many procedures and regression models that have been developed for improving PMI estimates involving VH analytes. The results of a descriptive study are also provided, highlighting the causes and distribution of mortality as registered in medico-legal autopsies performed in 2019 in Galicia (northwestern Spain), and revealing the use of these PMI estimation methods in real forensic practice. Great heterogeneity was detected in the collection of VH samples, the treatments to which they were subjected before examination, and in their conservation and analysis. A lack of reproducibility in the analytical methods employed to estimate [K +] and [Hx] was noted, as well as an absence of external validation for most of the regression formulae used to determine the PMI from analyte values. The use of methods based on high-performance liquid chromatography, focal electrophoresis, or thermogravimetric/chemometric procedures might solve the problems encountered with traditional analytical techniques, offering reliable results more quickly and effectively (even when samples are contaminated). This study recommends using flexible multiple regression models that combine physical and chemical variables, and that population databases be constructed so that models can be properly validated.

IPMICALC: an Integrated Post-mortem Interval Calculator.

Correctly estimating the post-mortem interval (PMI) is essential in forensic practice. In recent decades, the measurement of vitreous humor analyte concentrations - especially of hypoxanthine and potassium - and their correlation with the PMI have returned good results. However, calculating the PMI from the data collected can be quite complex. The present paper describes a web resource ( http://modestya.usc.es:3838/Forensic/ ) that simplifies the procedure. The PMI is determined (with its 95% confidence interval) in a rapid, easy, and reliable manner based on the use of mathematical models, the biochemistry of the vitreous humor, and physical variables such as the ambient temperature, the rectal temperature, and bodyweight. The application is entirely free to use.

Estimation of the post-mortem interval: Effect of storage conditions on the determination of vitreous humour [K+].

Obtaining a reliable estimate of the post-mortem interval (PMI) has been a long-running challenge in forensic medicine. Several more or less successful techniques for making such estimates have been developed, but in recent years important advances have been made thanks to the detailed study of the relationship between the PMI and the analytes - in particular K+ - of the vitreous humour (VH). The extraction and pre-treatment of VH samples has been standardized, the influence of certain environmental factors on analytical results has been quantified, and some of the circumstances under which techniques become unreliable have been identified. The present work examines how the conditions to which VH samples are subject in routine practice may alter the results of their analysis. Exposure to light and ambient temperature was found to alter the values returned in determinations of VH [K+], [Na+] and [Cl-], while exposure to several freezing/thawing cycles (even with final heating) led to no significant modifications in determinations of VH [K+] and [Na+]. It is recommended that if analysis has to be delayed, VH should be frozen for storage in a refrigerator before bringing to room temperature for processing. It is also recommended that samples not be exposed to ambient light and temperature.

Predicting Malaria Transmission Dynamics in Dangassa, Mali: A Novel Approach Using Functional Generalized Additive Models.

Mali aims to reach the pre-elimination stage of malaria by the next decade. This study used functional regression models to predict the incidence of malaria as a function of past meteorological patterns to better prevent and to act proactively against impending malaria outbreaks. All data were collected over a five-year period (2012-2017) from 1400 persons who sought treatment at Dangassa's community health center. Rainfall, temperature, humidity, and wind speed variables were collected. Functional Generalized Spectral Additive Model (FGSAM), Functional Generalized Linear Model (FGLM), and Functional Generalized Kernel Additive Model (FGKAM) were used to predict malaria incidence as a function of the pattern of meteorological indicators over a continuum of the 18 weeks preceding the week of interest. Their respective outcomes were compared in terms of predictive abilities. The results showed that (1) the highest malaria incidence rate occurred in the village 10 to 12 weeks after we observed a pattern of air humidity levels >65%, combined with two or more consecutive rain episodes and a mean wind speed <1.8 m/s; (2) among the three models, the FGLM obtained the best results in terms of prediction; and (3) FGSAM was shown to be a good compromise between FGLM and FGKAM in terms of flexibility and simplicity. The models showed that some meteorological conditions may provide a basis for detection of future outbreaks of malaria. The models developed in this paper are useful for implementing preventive strategies using past meteorological and past malaria incidence.

Spatio-Temporal Dynamic of Malaria Incidence: A Comparison of Two Ecological Zones in Mali.

Malaria transmission largely depends on environmental, climatic, and hydrological conditions. In Mali, malaria epidemiological patterns are nested within three ecological zones. This study aimed at assessing the relationship between those conditions and the incidence of malaria in Dangassa and Koila, Mali. Malaria data was collected through passive case detection at community health facilities of each study site from June 2015 to January 2017. Climate and environmental data were obtained over the same time period from the Goddard Earth Sciences (Giovanni) platform and hydrological data from Mali hydraulic services. A generalized additive model was used to determine the lagged time between each principal component analysis derived component and the incidence of malaria cases, and also used to analyze the relationship between malaria and the lagged components in a multivariate approach. Malaria transmission patterns were bimodal at both sites, but peak and lull periods were longer lasting for Koila study site. Temperatures were associated with malaria incidence in both sites. In Dangassa, the wind speed (p = 0.005) and river heights (p = 0.010) contributed to increasing malaria incidence, in contrast to Koila, where it was humidity (p < 0.001) and vegetation (p = 0.004). The relationships between environmental factors and malaria incidence differed between the two settings, implying different malaria dynamics and adjustments in the conception and plan of interventions.

A reliable method for estimating the postmortem interval from the biochemistry of the vitreous humor, temperature and body weight.

The estimation of the time elapsed since death is of paramount importance in the field of forensic sciences and criminal investigation, owing, among other factors, to the possible legal repercussions. Over the past few years various formulae have been developed to calculate this interval using a combination of different statistical methods and the concentrations of substances found in the vitreous humor. Corrective factors, such as ambient temperature, cause of death or age, which can modify the concentration of these substances and therefore the estimation of the postmortem interval, have been incorporated into models. In this paper five simple and reliable models to estimate PMI based the on the analysis of potassium, hypoxanthine and urea in the vitreous humor are presented. Corrective factors, such as body weight, rectal temperature and ambient temperature, which can influence the estimation of this interval have been incorporated into the formulae. Finally, the R2 and the mean squared error have been calculated for each model in order to select the best of the five. A free software program which calculates the PMI from the model and parameters used is available from the authors. It provides quick and reliable results as well as the error committed and R2 for each case.

Proposal for a new trajectory for subaxial cervical lateral mass screws.

PURPOSE: Lateral mass screws combined with rods are the standard method for posterior cervical spine subaxial fixation. Several techniques have been described, among which the most used are Roy Camille, Magerl, Anderson and An. All of them are based on tridimensional angles. Reliability of freehand angle estimation remains poorly investigated. We propose a new technique based on on-site spatial references and compare it with previously described ones assessing screw length and neurovascular potential complications. METHODS: Four different lateral mass screw insertion techniques (Magerl, Anderson, An and the new described technique) were performed bilaterally, from C3 to C6, in ten human spine specimens. A drill tip guide wire was inserted as originally described for each trajectory, and screw length was measured. Exit point was examined, and potential vertebral artery or nerve root injury was assessed. RESULTS: Mean screw length was 14.05 mm using Magerl's technique, 13.47 mm using Anderson's, 12.8 mm using An's and 17.03 mm using the new technique. Data analysis showed significantly longer lateral mass screw length using the new technique (p value < 0.00001). Nerve potential injury occurred 37 times using Magerl's technique, 28 using Anderson's, 13 using An's and twice using the new technique. Vertebral artery potential injury occurred once using Magerl's technique, 8 times using Anderson's and none using either An's or the new proposed technique. The risk of neurovascular complication was significantly lower using the new technique (p value < 0.01). CONCLUSION: The new proposed technique allows for longer screws, maximizing purchase and stability, while lowering the complication rate.

Predicting seasonal influenza transmission using functional regression models with temporal dependence.

This paper proposes a novel approach that uses meteorological information to predict the incidence of influenza in Galicia (Spain). It extends the Generalized Least Squares (GLS) methods in the multivariate framework to functional regression models with dependent errors. These kinds of models are useful when the recent history of the incidence of influenza are readily unavailable (for instance, by delays on the communication with health informants) and the prediction must be constructed by correcting the temporal dependence of the residuals and using more accessible variables. A simulation study shows that the GLS estimators render better estimations of the parameters associated with the regression model than they do with the classical models. They obtain extremely good results from the predictive point of view and are competitive with the classical time series approach for the incidence of influenza. An iterative version of the GLS estimator (called iGLS) was also proposed that can help to model complicated dependence structures. For constructing the model, the distance correlation measure [Formula: see text] was employed to select relevant information to predict influenza rate mixing multivariate and functional variables. These kinds of models are extremely useful to health managers in allocating resources in advance to manage influenza epidemics.

A valid method to determine the site of drowning.

The diatom test is considered a useful aid in determining the site of death from drowning. Nevertheless, there is disagreement within the scientific community concerning its reliability, and its findings have been challenged and sometimes overturned in courts of law. Using a model based on animal experimentation, we have developed a diatom test to discriminate between the locations of drowning sites from different aquatic systems. We carried out a complementary combination of quantitative and qualitative analyses together with a statistical analysis based on the Kullback-Leibler distance of the samples. A restrictive selection of exclusive diatom species from each reservoir was also made. This approach allowed us to validate the usefulness of the diatom test in determining the location of the site of drowning.

Estimating height from the first and second cervical vertebrae in a Spanish population.

One of the roles of forensic anthropology is the identification of skeletal remains and over the years many methods have been developed to obtain specific details of a corpse such as an estimation of age and height. The femur and tibia are ideal for this purpose but unfortunately they are often missing or badly fragmented. For this reason, in this present study, we used the smaller bones of the first and second cervical vertebrae, which are often better preserved than the long bones. Direct measurement of these bones has been found to be misleading, largely due to the remains of a covering of soft tissue, and to overcome this all measurements were taken from tomographic images. The aim of this study is to provide an auxiliary diagnostic method to evaluate the association of different anthropometric measurements taken with tomographic imagery of both the first cervical and second cervical vertebra with body height within a sample of the Spanish population. Measurements were taken from tomographic images taken with a dental CT of 203 healthy individuals from a Spanish population. The best correlation was obtained in the case of unknown sex using four measurements: two of the first cervical vertebra and two of the second vertebra using the following regression formula S=49.02+1.02O+1.58DO+0.49V+0.67I. All formulae provided statistically significant results and can be applied to any skeletal remains belonging to a Spanish population.

How reliable is the Spanish bodily harm assessment scale?

The use of scales to quantify or qualify bodily harm resulting from an unintentional car accident has been mandatory in Spain since 1995 and compensation for personal injuries resulting from a traffic accident is calculated according to a legal ruling established by Royal Decree 8/2004 (RDL). This present study assesses the reliability of the scale. Agreement between the evaluations for the same patient by 24 qualified observers following the Royal Decree 8/2004 was measured using the Kappa index. The variables assessed were the days of hospitalization, impeditive days, non impeditive days and the functional and aesthetic sequelae. The application of the Fleiss Kappa index obtained a result of 0.37, indicating a "fair agreement" according to the rating scale proposed by Landis and Koch. This study demonstrates the unreliability of the Spanish medical scale for the assessment of injury as described in the RDL 8/2004. The scale should adopt the measurement systems and clinical classifications of outcomes such as the ASIA, SCI scale or the Daniels scale of neurological injury and allow scientific discussion of the findings of the report. The resulting quantitative value should operate as a reliable indicator of a specific quality of the damage.

The use of computerized tomography in determining stature and sex from metatarsal bones.

This study evaluates the efficacy of a radiological method to estimate stature from measurements of the first and second metatarsal taken from a collection of metatarsals of a Portuguese Caucasian population in which the measurements were made directly on the bone. The highest coefficient of determination and the lowest standard error were obtained with the physiological length of the second metatarsal (F2), using the equation S=895.4803+10.7848F2. The linear regressions obtained show significant differences between the estimated heights from M1. In addition, we offer a simple method for sex determination based on the maximum length (M1) and width (W1) of the first metatarsal, where W1=x1; (M1/W1)=x2; ß0=55.4767; ß1=-2.5796 and ß2=-4.6898. Here we present a method of measurement using computerized tomography that enables population studies using live volunteers without incurring the difficulties of on the bone measurement.

Estimating adult stature from radiographically determined metatarsal length in a Spanish population.

The ability to determine height in adult life can be crucial in the identification of skeletal remains. Very often, the small bones found among such remains are not only the most numerous, but also the best preserved, a fact which calls for more research into developing methods to estimate height from metatarsals. The aim of this paper is to verify the use of the dimensions of the metatarsals as estimators of adult height in a Spanish population using radiologically determined metatarsal lengths and to propose regression equations and test the formulae for determining adult stature. The present research is based on a study of 228 healthy Caucasoid adults from Galicia (NW Spain). The first and second metatarsals of the left foot were measured by a dorso-plantar X-ray using a digital medical image viewer. The best correlation obtained was with the maximum length of the 1st metatarsal for males. The corresponding regression equation is as follows: S=819.88+12.79 M1. A comparison of our statistical results with those of neighbouring population groups indicates that ours is more accurate. This must be due to the so-called specificity of regression equations in relation to the series on the base from which they were developed.

Extending induced ROC methodology to the functional context.

The receiver operating characteristic (ROC) curve is the most widely used measure for evaluating the discriminatory performance of a continuous marker. Often, covariate information is also available and several regression methods have been proposed to incorporate covariate information in the ROC framework. Until now, these methods are only developed for the case where the covariate is univariate or multivariate. We extend ROC regression methodology for the case where the covariate is functional rather than univariate or multivariate. To this end, semiparametric- and nonparametric-induced ROC regression estimators are proposed. A simulation study is performed to assess the performance of the proposed estimators. The methods are applied to and motivated by a metabolic syndrome study in Galicia (NW Spain).

PMICALC: an R code-based software for estimating post-mortem interval (PMI) compatible with Windows, Mac and Linux operating systems.

In legal medicine the correct determination of the time of death is of utmost importance. Recent advances in estimating post-mortem interval (PMI) have made use of vitreous humour chemistry in conjunction with Linear Regression, but the results are questionable. In this paper we present PMICALC, an R code-based freeware package which estimates PMI in cadavers of recent death by measuring the concentrations of potassium ([K+]), hypoxanthine ([Hx]) and urea ([U]) in the vitreous humor using two different regression models: Additive Models (AM) and Support Vector Machine (SVM), which offer more flexibility than the previously used Linear Regression. The results from both models are better than those published to date and can give numerical expression of PMI with confidence intervals and graphic support within 20 min. The program also takes into account the cause of death.

Flexible regression models for estimating postmortem interval (PMI) in forensic medicine.

Correct determination of time of death is an important goal in forensic medicine. Numerous methods have been described for estimating postmortem interval (PMI), but most are imprecise, poorly reproducible and/or have not been validated with real data. In recent years, however, some progress in PMI estimation has been made, notably through the use of new biochemical methods for quantifying relevant indicator compounds in the vitreous humour. The best, but unverified, results have been obtained with [K+] and hypoxanthine [Hx], using simple linear regression (LR) models. The main aim of this paper is to offer more flexible alternatives to LR, such as generalized additive models (GAMs) and support vector machines (SVMs) in order to obtain improved PMI estimates. The present study, based on detailed analysis of [K+] and [Hx] in more than 200 vitreous humour samples from subjects with known PMI, compared classical LR methodology with GAM and SVM methodologies. Both proved better than LR for estimation of PMI. SVM showed somewhat greater precision than GAM, but GAM offers a readily interpretable graphical output, facilitating understanding of findings by legal professionals; there are thus arguments for using both types of models. R code for these methods is available from the authors, permitting accurate prediction of PMI from vitreous humour [K+], [Hx] and [U], with confidence intervals and graphical output provided.

Prediction of SO2 levels using neural networks.

In this paper, we present an adaptation of the air pollution control help system in the neighborhood of a power plant in As Pontes (A Coruña, Spain), property of Endesa Generación S.A., to the European Council Directive 1999/30/CE. This system contains a statistic prediction made half an hour before the measurement, and it helps the staff in the power plant prevent air quality level episodes. The prediction is made using neural network models. This prediction is compared with one made by a semiparametric model.