Geographic variation in left ventricular mass and mass index: a systematic review.

Left ventricular (LV) hypertrophy, defined as an abnormal increase in LV mass (LVM), is an important prognostic indicator and therapeutic target. LVM is often divided by body surface area to derive indexed mass; however, this does not correctly identify pathological LV hypertrophy in all people, especially when body composition is altered, or in different ethnic groups. We evaluated published ranges of echocardiographic LVM in healthy adult populations from different countries, excluding control groups, and compared them with the American Society of Echocardiography reference ranges. A total of 33 studies met the inclusion criteria. In men and women, there was wide variation in the ranges of LVM with a tendency for the upper limit to increase geographically westward; this variation remained for indexed mass. Several ranges fell outside the upper reference limits: in men, 13 of the mass ranges and 16 of indexed mass; and in women, 8 mass and 16 indexed mass. This review has shown that current guidelines may need revision as some published series suggest that greater LV mass should be considered normal. This may be explained by ethnic differences and supports the need for widely applicable and ethnically diverse reference ranges to be established.

Role of echocardiographic left ventricular mass and carotid intima-media thickness in the cardiovascular risk assessment of asymptomatic patients with type 2 diabetes mellitus.

BACKGROUND: Standard cardiovascular (CV) risk assessment may underestimate risk in people with type 2 diabetes mellitus (T2DM). Cardiac and vascular imaging to detect subclinical disease may augment risk prediction. This study investigated the association between CV risk, left ventricular hypertrophy (LVH) and carotid intima-media thickness (CIMT) in patients with T2DM free of CV symptoms. METHODS: People with T2DM without known CV disease were recruited from general practice. The 5-year risk of CV events was calculated using an adjusted Framingham equation and the prevalence of LVH and abnormal CIMT across bands of CV risk assessed. In those at intermediate risk, the number needed to scan (NNS) to reclassify one person to high risk was calculated across the group and compared in those above and below 55 years. The association between LV mass and CIMT was also assessed. RESULTS: Mean age 57 years (SD11), 51% female. Median 5-year CV risk 14.3% (interquartile range 10.3, 19.5), 51% had LVH (American Society of Echocardiography criteria) and 31% an abnormal CIMT (age and sex criteria). In the 52% at intermediate risk, 37% had LVH and 36% an abnormal CIMT. The NNS was 1.7 using both imaging techniques, 2.7 using cardiac imaging alone or 2.8 using vascular imaging alone. Almost twice as many people >55 years had an abnormal CIMT than those <55 years. CONCLUSIONS: Cardiac and vascular imaging to detect subclinical disease can be used to augment prediction of CV risk in people with T2DM at intermediate risk. The value of reclassifying risk is as yet unproven and requires outcome data from intervention studies.

An extended likelihood ratio framework for interpreting evidence.

This paper reviews some current methods, the likelihood ratio-based approach and the full Bayesian approach for the interpretation of evidence and discusses previously identified shortcomings in them. It suggests an approach based on a compromise--based on an extended likelihood ratio--that may combine the merits of logic without overstepping acceptable bounds for the forensic scientist in the presentation of evidence. The approach is exposed formally and takes advantage of inferential networks called Bayesian networks.

The sensitivity of the Bayesian HPD method to the choice of prior.

Statistical sampling error is present in every statistical calculations using DNA because all such statistics rely on a sample (database) of individuals, which is used to estimate the population frequencies of alleles. Curran et al.gave a method for estimating the sampling error of the statistics based on the region of the highest density of the Bayesian posterior (HPD). The Bayesian HPD method relies on the assumption of a prior distribution for the population allele frequencies as well as Monte Carlo simulation. In this paper we answer three pivotal questions. Firstly we address the question of how many Monte Carlo iterations are required to get sufficient accuracy in our estimates of sampling error. Secondly, we address the question of the appropriate choice of the prior distribution for the population allele frequencies. Thirdly, we demonstrate the flexibility of the Bayesian HPD over other methods.

A model for estimating the number of glass fragments transferred when breaking a pane: experiments with firearms and hammer.

Numerous publications have shown the importance of transfer in the interpretation of glass evidence. As this phenomenon is also highly variable, it was decided to test the hypothesis that there exists a means to predict the number of fragments recovered at time t = 0. Panes of float glass-of different types and thickness-were broken using either a firearm or a hammer. It was decided to choose a firearm as the main breaking device, as it allowed not only to have more reproducible conditions but also to acquire knowledge in a field where little has been published. Despite the inherent variation in the breaking process, the results show that using a statistical model it is possible to predict the number of fragments transferred onto a garment from the number of fragments transferred to the ground. This research also indicates the size and number of particles transferred onto a person, when breaking window panes of different types (float, laminated or toughened) with different breaking procedures.

The two trace transfer problem re-examined.

The classical two trace transfer problem initially discussed by Evett is reconsidered [Evett IW. On Meaningful Questions: A Two-Trace Transfer Problem. Journal of the Forensic Science Society 1987; 27: 375-381]. In this problem we consider the situation where there are two stains of differing types at a crime scene. Evett considered the situation where both are known to be relevant to the offence. It was further assumed that there were exactly two offenders. Reanalysis of this problem suggests that the key consideration is the conditioning on there being exactly two offenders, not that there were two stains. The treatment here leads easily to a generalisation in which stains have differing relevance and there are k offenders.

Effects of population structure and admixture on exact tests for association between Loci.

The probability of multilocus genotype counts conditional on allelic counts and on allelic independence provides a test statistic for independence within and between loci. As the number of loci increases and each sampled genotype becomes unique, the conditional probability becomes a function of total heterozygosity. In that case, it does not address between-locus dependence directly but only indirectly through detection of the Wahlund effect. Moreover, the test will reject the hypothesis of allelic independence only for small values of heterozygosity. Low heterozygosity is expected for population subdivision but not for population admixture. The test may therefore be inappropriate for admixed populations. If individuals with parents in two different populations are always considered to belong to one of the populations, then heterozygosity is increased in that population and the exact test should not be used for sparse data sets from that population. If such a case is suspected, then alternative testing strategies are suggested.

Assessing uncertainty in DNA evidence caused by sampling effects.

Sampling error estimation in forensic DNA testimony was discussed. Is an estimate necessary and how should it be made? The authors find that all modern methods have areas of strength and weakness. The assessment of which is the 'best' is subjective and depends on the performance of the method, the type of problem (criminal work or paternity), the database size and availability of computing software and support. The authors preferred the highest posterior density approach for performance, however the other methods all have areas where their performance is adequate. For single-contributor stains normal approximation methods are suitable, also the bootstrap and the highest posterior density method. For multiple-contributor stains or other complex situations the match probability expressions become quite complex and it may not be possible to derive the necessary variance expressions. The highest posterior density or the bootstrap provide a better general method, with non-zero theta. The size-bias correction and the factor of 10 approaches may be considered acceptable by many forensic scientists as long as their limitations are understood.

Glass on clothing and shoes of members of the general population and people suspected of breaking crimes.

The outer clothing and footwear of 122 people attending a university gymnasium and a private gymnasium were searched for fragments of glass. Both the surfaces and the pockets of the clothing and the uppers and soles of the footwear were searched. New Zealand forensic glass cases have been reviewed to determine the amount of non-matching glass present on the clothing of people who are suspected of breaking crimes. Data from 114 suspects who had no matching glass on their clothing and shoes were accumulated. Statistical modelling techniques have been applied to the data collected.

Relationships within the Proteobacteria of plant pathogenic Acidovorax species and subspecies, Burkholderia species, and Herbaspirillum rubrisubalbicans by sequence analysis of 16S rDNA, numerical analysis and determinative tests.

Sequence data for 16S rDNA of the type strains of Acidovorax avenae subsp. avenae, A. avenae subsp. cattleyae, A. avenae subsp. citrulli, A. konjaci and Herbaspirillum rubrisubalbicans were compared with GenBank library accessions of Burkholderia spp., Comamonas sp., Ralstonia solanacearum and Variovorax sp. Maximum Parsimony analysis produced two clusters: 1. Acidovorax spp., Comamonas sp., and Variovorax sp. (all in the Comamonadaceae), and 2. Burkholderia spp., Ralstonia solanacearum, and Herbaspirillum rubrisubalbicans. Maximum Likelihood analysis produced only one cluster (of the Comamonadaceae). Using nutritional and laboratory tests, all Acidovorax spp., Burkholderia spp., and Herbaspirillum rubrisubalbicans were discriminated in distinct clusters at the species level, and could be identified by selected determinative tests. There were no phenotypic tests constituted as a circumscription of the genera and which permitted the allocation of strains to genera. Strain identification as species allowed allocation to genera only by inference. The nomenclatural implications of these data are discussed.

The calculation of DNA match probabilities in mixed race populations.

A coherent method is offered to estimate likelihood ratios for DNA match probabilities from mixed racial populations that avoids the approach of reporting separate estimates for each race. The method is demonstrated for some cases involving profiles derived from several individuals and incorporates a correction for 'subpopulation' effects.

Interpreting DNA mixtures in structured populations.

DNA profiles from multiple-contributor samples are interpreted by comparing the probabilities of the profiles under alternative propositions. The propositions may specify some known contributors to the sample and may also specify a number of unknown contributors. The probability of the alleles carried by the set of people, known or unknown, depends on the allelic frequencies and also upon any relationships among the people. Membership of the same subpopulation implies a relationship from a shared evolutionary history, and this effect has been incorporated into the probabilities. This acknowledgment of the effects of population structure requires account to be taken of all people in a subpopulation who are typed, whether or not they contributed to the sample.

Assessing transfer probabilities in a Bayesian interpretation of forensic glass evidence.

When someone breaks glass a number of tiny fragments may be transferred to that person. If the glass is broken in the commission of a crime then these fragments may be used as evidence. A Bayesian interpretation of this evidence relies on the forensic scientist's ability to assess the probability of transfer. This paper examines the problem of assessing this probability and suggests some solutions.

Sampling in forensic comparison problems.

When someone breaks glass a number of tiny fragments may be transferred to that person. If the glass is broken in the commission of a crime then these fragments may be used as evidence. If a large number of fragments are recovered from the suspect, then it may be more efficient for the forensic scientist to examine a subset of these fragments. Such sampling incurs information loss. This paper will derive an expression that allows a partial quantification of this loss. The loss of such information due to the examination of a subset of recovered material arises with many forms of evidence.

Adsorption of a hydrophobic mutagen to cereal brans and cereal bran dietary fibres.

The abilities of brans from the cereals barley, oats, maize, rice, and wheat to adsorb in vitro the hydrophobic, environmental mutagen 1,8-dinitropyrene (DNP) were investigated using a mutagenicity assay. These brans were obtained from known cultivars using defined milling conditions and were chemically characterised. The abilities of total and insoluble dietary fibre preparations obtained from these brans to adsorb DNP were also investigated. The predicted weight of each bran required to adsorb 50% of the added DNP was used to compare the adsorptive abilities of the different brans. The brans were ranked in the order (most effective to least effective): rice, wheat, maize, barley, and oats. The adsorptive abilities of the dietary fibre preparations were not significantly different from the bran from which they were prepared. However, if the dietary fibres (cell walls) were the only components adsorbing the DNP, we would have expected the dietary fibre preparations to have adsorbed more DNP than the equivalent unextracted bran. This suggests that other components, probably starch, also adsorb DNP in the unextracted brans. It is not known why brans from different cereal species differ in adsorptive ability but the lignified cell walls in wheat bran may be important in conferring good adsorptive properties to this bran. The possible relationship between adsorptive ability and ability of the bran from a particular species to protect against colorectal cancer is discussed.

Combining a continuous Bayesian approach with grouping information.

When someone breaks glass a number of tiny fragments may be transferred to that person. If the glass is broken in the commission of a crime then these fragments may be used as evidence. A Bayesian interpretation of this evidence relies on, among other things, the forensic scientist's ability to assess the likelihood that the glass recovered from the suspect may have come from more than one source. This paper will examine the effect of including this information in the interpretation. We envisage working towards a system whereby the information loss that occurs during the normal casework activities of sample selection and glass fragment grouping is quantified.

Interpreting DNA mixtures.

The interpretation of mixed DNA stains is explained in the context of likelihood ratios. The probabilities for the mixed-stain profile are evaluated under alternative explanations that specify the numbers of contributors and the profiles of any known contributors. Interpretations based simply on the frequencies with which random members of a population would not be excluded from a mixed-stain profile do not make use of all the information, and may overstate the strength of the evidence against included people. The effects of the numbers of contributors depends on whether all the alleles at a locus are present in the mixed stain. A general equation is given to allow likelihood ratios to be calculated, and includes the "2p" modification suggested by the 1996 NRC report. This modification is not always conservative. A computer program to perform calculations is available.

The adsorption of heterocyclic aromatic amines by model dietary fibres with contrasting compositions.

It is often recommended that consumption of dietary fibre should in increased to protect against colorectal cancer. However, although more than 95% of dietary fibre is contributed by whole plant cell walls, very little experimental work has been done using whole plant cell walls. These may protect by adsorbing carcinogens, thus lowering their effective concentration in the alimentary tract, and by carrying the carcinogens out of the body in the faeces. However, plant cell walls vary widely in their composition and physical properties, and not all cell walls will necessarily have protective properties. We therefore isolated 4 plant cell-wall preparations with contrasting compositions as models of the types of cell walls that occur in the diet. We investigated the abilities of these preparations to adsorb in vitro 6 heterocyclic aromatic amines (HAAs). HAAs occur in the human diet and several are colon carcinogens, at least in rats. We found that the ability of the HAAs to adsorb to the plant cell walls increased with increasing hydrophobicity of the HAA, measured as the calculated logarithm of the partition coefficient between 1-octanol and water (C logP). A cell-wall preparation containing mainly the walls of parenchyma cells (the most common cell type in food plants) had only poor adsorptive ability. A cell-wall preparation from commercial cork had the best adsorptive ability. This preparation was the most hydrophobic of those examined because the cell walls contained the polymer, suberin, together with associated waxes. The preparation modelled suberized cell walls which occur in the diet, for example in potato skins. The other two cell-wall preparations contained another hydrophobic polymer, lignin, and had intermediate adsorptive abilities which were not significantly different from one another. These preparations modelled lignified cell walls which occur in the diet, for example in wheat bran. Our results indicate that suberized and lignified cell walls may be important in protecting against colorectal cancer.

The effects of a soluble-fibre polysaccharide on the adsorption of carcinogens to insoluble dietary fibres.

Epidemiology and animal experiments indicate that dietary fibres protect against the development of colorectal cancer. However, insoluble dietary fibres appear to be more effective than soluble dietary fibres and one mechanism by which they may protect is by adsorbing dietary carcinogens. We found previously that the ability of a carcinogen to adsorb in vitro to alpha-cellulose (a model insoluble dietary fibre) was strongly related to the hydrophobicity of the carcinogen, measured as the calculated logarithm of the partition coefficient between 1-octanol and water (C log P). Furthermore, soluble dietary fibres (soluble-fibre polysaccharides), including gum arabic, reduced the adsorption of the hydrophobic carcinogen, DNP, to alpha-cellulose. In the present study we tested the ability of gum arabic to reduce the adsorption in vitro of the carcinogens BaP (C log P = 6.124), DNP (C log P = 4.384), and the heterocyclic amines, Trp-P-1 (C log P = 3.230) and MeIQx (C log P = 1.078). Gum arabic reduced the adsorption to alpha-cellulose of BaP and DNP, but not the adsorption of Trp-P-1 or MeIQx. Gum arabic also reduced the adsorption of BaP to an insoluble, dietary-fibre preparation from commercial cork which contains the hydrophobic component, suberin, but did not affect the adsorption of DNP, Trp-P-1 or MeIQx. It also did not affect the adsorption of DNP to an insoluble, dietary-fibre preparation from wheat straw, which contains the hydrophobic component, lignin. The results are discussed in terms of hydrophobic interactions between carcinogens and insoluble dietary fibres. In vivo, it is likely that soluble dietary fibres reduce the adsorption of only highly hydrophobic carcinogens to some insoluble dietary fibres.