Use Of Percentiles Research Articles

S-43-1: THE CHANGING EPIDEMIOLOGY OF HYPERTENSION IN CHILDREN AND ADOLESCENTS

Some scientific concepts take time to overcome initial disbelief before they are finally embraced by the research community. One of these concepts is hypertension in children and adolescents. Little was known about childhood hypertension until the early 1980 s, mainly because blood pressure was not commonly measured in pediatric clinical practice. In the few cases blood pressure levels were determined to be abnormal in children, they were considered to be secondary hypertension resulting from an underlying condition. Even though secondary causes of hypertension tend to occur more often in hypertensive children than in adults, its prevalence is only about 1 percent overall, leaving primary hypertension especially in adolescents as the most frequent type. Even when there are many studies that have assessed the prevalence of hypertension in children and adolescents, scientists have faced difficulties to state this prevalence for three main reasons. To begin with, blood pressure normally changes with increasing age and body size. This makes establishing a fixed cutoff for values of systolic and diastolic blood pressure elevation rather challenging. This difficulty has led to the use of percentiles based on age, sex, and height to define the normal distribution, with a hypertensive level of blood pressure in the 95th percentile or higher. Another obstacle is that there is a variety of different definitions of hypertension used by the three most recent clinical practice guidelines coming from Europe, the United States and Canada. The last challenge is focused on the beat-to-beat blood pressure variability, the definition of hypertension requires that systolic and/or diastolic blood pressure to be persistently higher than the established thresholds on three separate occasions. Many cross-sectional studies with only one single measurement of blood pressure have not been able to define the prevalence of hypertension. The epidemiology of hypertension in childhood and adolescence can be linked to the worldwide obesity epidemic. Hypertension is more prevalent than before, with primary hypertension being the main type. It is well known that the factors related to primary hypertension can be modified, therefore childhood is a period in which prevention could be effective. If prevention is followed throughout childhood, it could contribute to a healthier young adulthood in the long run. Therefore, primordial prevention is an opportunity not to be missed.

A-38 A Different Approach for Examining Gender Differences on Computerized Neurocognitive Testing: Percentile Ranks Versus Composite Scores

Abstract Objective ImPACT is a popular tool used to assess neurocognitive function after concussion. Age- and gender-based percentile ranks are provided as part of the ImPACT clinical report, but only raw composite scores are provided for research. Percentile ranks may provide an alternate look at gender differences on neurocognitive testing. We sought to compare the use of percentile ranks versus composite scores when comparing neurocognitive performance between male and females. Method Pre-season baseline data from 3,238 collegiate athletes were exported from a larger multi-site database, 1,714 male (53%) and 1,524 female (47%), ages 18–22 (Mean = 19.3, SD = 1.2). ImPACT composite scores were extracted (Verbal Memory, Visual Memory, Visual Motor Speed, Reaction Time) and Percentile Ranks were calculated using age- and gender-based reference tables in the ImPACT 2017–2012 Technical Manual. One-way analyses of variance (ANOVA) were conducted with gender as the IV and the four composite scores and their associated percentile ranks as the DVs. Bonferroni correction for 8 comparisons set the alpha level to p < .006. Results ANOVAs revealed a significant effect of gender on ImPACT Verbal Memory [F(1,3236) = 16.32, p < .001], Visual Memory [F(1,3236) = 66.06, p < .001], Visual Motor Speed [F(1,3236) = 15.61,p < .001] but not Reaction Time [F(1,3236) = 2.59, p = .11]. When using percentile ranks, ANOVAs revealed a significant effect of gender on only Visual Motor Speed [F(1,3236) = 31.07, p < .001], but not Verbal Memory [F(1,3236) = 2.43, p = .12], Visual Memory [F(1,3236) = 0.48, p = .49], or Reaction Time [F(1,3236) = 0.61, p = .44]. Conclusions Use of ImPACT Composite Scores in concussion research may exaggerate or inappropriately promote gender differences on computerized neurocognitive testing. Given that age- and gender-based normative data are available, use of percentile ranks is recommended.

Updates on Assessment and Monitoring of the Postnatal Growth of Preterm Infants.

Assessing and monitoring the physical growth of preterm infants is fundamental to NICU care. The goals of nutritional care are to approximate the growth and body composition of the healthy fetus and to support optimal brain development while minimizing future cardiometabolic risk. Both poor and excessive growth predict adverse long-term health outcomes. Growth curves are clinical tools used to assess the preterm infant's growth status. Several growth curves for preterm infants were developed in the past decade. To use them effectively, clinicians need to understand how each growth curve was developed; the underlying reference population; intended use; and strengths and limitations. Intrauterine growth curves are references that use size at birth to represent healthy fetal growth. These curves serve 2 purposes-to assign size classifications at birth and to monitor postnatal growth. The INTERGROWTH-21 st preterm postnatal growth standards were developed to compare the postnatal growth of preterm infants to that of healthy preterm infants rather than the fetus. Individualized weight growth curves account for the water weight loss that frequently occurs after birth. In addition, body mass index (BMI) curves are now available. In this review, we discuss the main characteristics of growth curves used for preterm infants as well as the use of percentiles, z scores, and their change over time to evaluate size and growth status. We also review the differences in body composition between preterm infants at term-equivalent age and term-born infants and the potential role of monitoring proportionality of growth using BMI curves.

Principal component analysis: The path ahead for aircrew-aircraft compatibility at the Institute of Aerospace Medicine

Introduction: The Institute of Aerospace Medicine provides design consultancy on aircraft-aircrew compatibility on a number of fixed-wing as well as rotary-wing aircrafts during various stages of development. Till date, the cockpit compatibility of aircrew has been determined based on the percentile concept. Percentiles, though useful when dealing with a single parameter, pose major design and fitment problems when considering multiple parameters simultaneously as in aircraft cockpit design. The concept of multivariate analysis has been the solution which the aviation industry the world over has accepted in overcoming this problem. This paper presents the Institute of Aerospace Medicine initial foray into the field of multivariate analysis, specifically principal component analysis (PCA) to achieve desired aircrew fitment in the aircraft cockpit right from the design stage. Materials and Methods: The fighter aircraft of the near future is being designed using the anthropometric parameters available in the IAF aircrew anthropometry survey 2013. Of the 57 parameters available, six parameters critical to the design of the cockpit were subject to PCA to derive three principal components. About 96% confidence ellipse was drawn on the plot of the principal components. From this, along the different axes, 21 boundary individuals were identified defining the extreme individuals in various combinations of the six parameters. Discussion: The use of more than 2 parameters is not amenable to sequential use of percentiles. As the number of parameters considered increases, it leads to reduced fitment percentage. The use of PCA allows consideration of critical parameters together at one go. The design aim is changed from the 3rd to 97th percentile to an overall aim of fitting 96% of the target population in the cockpit. The boundary individual’s entire anthropometry data are used to create boundary manikins for use in computer-aided design models. The fitment of these boundary individuals ensures that if these individuals fit, all others would fit in the cockpit. This concept brings about a paradigm shift in the aircrew-aircraft compatibility in the aviation industry in India.

Influence of Physical Activity on Blood Pressure in Children With Overweight/Obesity: A Randomized Clinical Trial.

The prevalence of childhood hypertension (HT) is growing exponentially, influenced by environmental factors such as foods with high salt content, sedentary lifestyles, and poor-quality food. The incidence of HT is about 10.4% in well-nourished children, but when associated with obesity or overweight, this can rise to 38% and 68%, respectively. To assess the influence of physical activity on the blood pressure (BP) of children who are overweight or obese. This randomized clinical trial was carried out in Granada (Spain), from October 2015 to June 2016. The sample consisted of 98 children, all of whom were overweight or obese. The intervention group (IG) (n = 49) practised physical activity and received nutritional advice, while the control group (n = 49) only received theoretical-practical sessions on nutrition. Body composition was measured, a nutritional assessment was made and BP was determined (in percentiles, to avoid the misclassification of children who are located at the extremes of normal growth). Before the physical activity intervention, 85.7% of the children in the IG (with overweight/obesity) were in the 95th or higher percentile for BP, a situation representative of high BP (HT). However, by the end of the study period, this value had decreased significantly (P = 0.001), to 16.13%. Childhood obesity is a risk factor for HT. Physical activity, together with nutritional advice, effectively reduces BP in children who are overweight or obese. The use of percentiles, according to age, weight, and height, is an effective means of measuring BP. This study is registered at https://www.clinicaltrials.gov (identifier NCT02779647).

2159. Methodological Threats to the Standardized Infection and Standardized Antimicrobial Administration Ratios

BackgroundStandardized ratios, such as the CDC’s Standardized Infection Ratio (SIR) and Standardized Antimicrobial Administration Ratio (SAAR), are used to assess hospital infection control and stewardship programs. While there has been a focus to improve adjustment factors in the prediction models for these ratios, there remain limitations to these methods in assessments of program effects.MethodsWe use a previously published mathematical model of an intensive care unit to simulate transmission of Staphylococcus aureus and the administration of antimicrobials to treat it. This approach allows for the calculation of an MRSA LabID SIR and Anti-MRSA adult ICU SAAR score with perfect adjustment, where the only difference between the simulated ICUs is due to random chance. We then evaluated the interpretations and statistical significance of these ratio measures as gauges of hospital program performance.ResultsOver a single year of 200 simulations, the models produced SIR/SAAR scores ranging from 0.47 to 1.73, with a median of 0.99, representing a considerable spread of scores obtained due to chance. The P-values measuring if these measures were different from 1.0 were significant in 86% of those facilities. Extending the simulation past one year exacerbated this tendency to over-identify scores as significant, and also showed that 53.5% of hospitals had improving (26%) or worsening (27.5%) of scores due to regression to the mean. This scenario could be falsely interpreted as the result of interventions put in place in response to their first year scores.ConclusionStandardized ratio methods did not provide clear and actionable information, even with perfect adjustment. Statistically significant fluctuations occurred due to chance which could be mistakenly been attributed to actions taken by the hospital. Several methods, such as the use of percentiles rather than p-values, or presenting simulation-based projections of facility data, may help alleviate these problems.Disclosures All authors: No reported disclosures.

Optimal Designs of the Variable Sample Size Chart Based on Median Run Length and Expected Median Run Length

The variable sample size (VSS) chart, devoted to the detection of moderate mean shifts, has been widely investigated under the context of the average run‐length criterion. Because the shape of the run‐length distribution alters with the magnitude of the mean shifts, the average run length is a confusing measure, and the use of percentiles of the run‐length distribution is considered as more intuitive. This paper develops two optimal designs of the VSS chart, by minimizing (i) the median run length and (ii) the expected median run length for both deterministic and unknown shift sizes, respectively. The 5th and 95th percentiles are also provided in order to measure the variation in the run‐length distribution. Two VSS schemes are considered in this paper, that is, when the (i) small sample size (nS) or (ii) large sample size (nL) is predefined for the first subgroup (n1). The Markov chain approach is adopted to evaluate the performance of these two VSS schemes. The comparative study reveals that improvements in the detection speed are found for these two VSS schemes without increasing the in‐control average sample size. For moderate to large mean shifts, the optimal VSS chart with n1 = nL significantly outperforms the optimal EWMA chart, while the former is comparable to the latter when n1 = nS. Copyright © 2016 John Wiley & Sons, Ltd.

Born Large for Gestational Age: Bigger Is Not Always Better

Born Large for Gestational Age: Bigger Is Not Always Better

Síndrome metabólico en niños: problemática, componentes y criterios diagnósticos

Background : The metabolic syndrome in children increases the risk for type 2 diabetes and cardiovascular disease in adulthood. Aim : To describe the components of metabolic syndrome in children, their prevalence, and diagnostic criteria proposed by different authors and organizations. Materials and methods : A literature search of articles published in Pubmed, Science Direct, Embase, Lilacs and Scielo databases was conducted. Results and discussion: Several organizations have established definitions for metabolic syndrome diagnosis in children, some including criteria used for adults or adopting cutoffs derived from selected populations such as obese children or without including pre-adolescent children, arguing a low prevalence of alterations in these. Thus, the prevalence of metabolic syndrome in a particular population varies (0,9% to 11,4%) according to the definition used. However, this prevalence increases according to the obesity grade, and a high prevalence in pre-pubers has been reported, independent of the classification used. Recently, it was proposed the use of a continuous score to improve the metabolic syndrome evaluation in children. Conclusion : The cutoffs currently used give different weighting for each component of metabolic syndrome. Therefore, it is recommended the use of percentiles according to sex and age and population for each component and to evaluate the utility of continuous scores in this population.

Вопросы оценки постнатального роста недоношенных детей Часть 2. Догоняющий рост недоношенных детей

The term catch-up growth is now widely used in neonatology and pediatrics to describe the growth of preterm infants. Catch-up growth — is a compensatory strengthening of the body's growth after a period of slow growth. The lower the gestational age of the premature baby, the more intense catch-up growth in the future.Catch-up growth is considered an important criterion for evaluating nursing preterm infants. Formation of catch-up growth is seen as a favorable outcome. Evaluation of catch-up growth is carried out with the use of percentiles and standard deviations (Z - score). Catch-up growth has a positive effect on neurological outcome. Catch-up growth achieved if the growth rates are between 5 and 10 percentile. The values of growth are satisfactory if they are located at the 10th percentile and above. Catch-up growth is achieved with a standard deviation greater than minus 2 (Z - score). The optimal parameters are considered indicators located within two standard deviations of the mean.Estimation of the growth should be carried out optimally weekly. Growth curves help to determine when the catch-up growth begins. After discharge from the hospital catch-up growth continues. Catch-up growth occurs within the first year of life. The critical period for catch-up growth are considered the first 6 months. Subsequently, the growth rate decreases. The growth is not sufficient, if the values are below the 3 percentile. About 50% of the causes impaired growth is due to the shortage of supply. Premature babies can have problems with food and after discharge from the hospital. The very rapid growth may lead to the development of metabolic syndrome in later life. Low birth weight is associated with increased risk of hypertension, stroke, and diabetes. Compensatory growth often occurs with excessive deposition of fat. In assessing the growth necessary to accommodate the growth of muscle mass and fat mass. Maintaining optimal growth rate is important for the prevention of metabolic syndrome. Requires a meta-analysis of all published growth curves for premature babies to determine the optimal postnatal growth.

An Appraisal of Skilled Labour Migration in Nigerian Construction Industry

The inability of employers to get employable professionals to fill vacancies may have taken its toll on the Nigerian Construction Industry. This scenario may not be unconnected with the global demand for skilled workers and the search for greener pasture. This research identified why professionals leave the Nigerian Construction Industry in droves and explored the effect of these on project delivery in the Nigerian Construction Industry. A survey research design was employed for the research and the research objectives were achieved through the use of percentile and relative importance index method of data analysis. It was gathered that there was an external economic pull on the Nigerian Construction Industry as a result of better wages, political stability, social stability, health insurance etc. To arrest and reverse this development it was recommended that economic, political and social climate be made conducive so that qualified hands can be retained and those in diasporas can be encouraged to return home.

The use of percentiles and percentile rank classes in the analysis of bibliometric data: Opportunities and limits

Percentiles have been established in bibliometrics as an important alternative to mean-based indicators for obtaining a normalized citation impact of publications. Percentiles have a number of advantages over standard bibliometric indicators used frequently: for example, their calculation is not based on the arithmetic mean which should not be used for skewed bibliometric data. This study describes the opportunities and limits and the advantages and disadvantages of using percentiles in bibliometrics. We also address problems in the calculation of percentiles and percentile rank classes for which there is not (yet) a satisfactory solution. It will be hard to compare the results of different percentile-based studies with each other unless it is clear that the studies were done with the same choices for percentile calculation and rank assignment.

Shannon Conduction Heterogeneity Index – A Novel Way of Characterisation of Heterogeneity of the Wave Conduction in Heart Muscle Using Shannon Entropy

Introduction: Heterogeneity of conduction is believed to be a critical feature of the atrial fibrillation substrate. To date, Conduction Heterogeneity Index (CHI) calculated frompercentiles of the phasemaphistogram is used. Unfortunately, use of percentiles introduces sensitivity to extreme points in histogram. We hypothesise that Shannon Entropy, a measure of information content, provides better assessment of conduction heterogeneity. Methods: We used Shannon’s Entropy to quantify CHI in superfused left atria from 14male SpragueDawley rats. High density multiple electrode array was used to obtain activationmapsduringpacingat twocycle lengths, 100and 400ms with additional decremental premature stimulus. Conduction event just before reaching refractory period was taken for analysis. In addition, we performed numerical simulations on 2D model of heart tissue in which we introduced random disturbance of cell coupling resulti p 1

Nutrient and oxygenation conditions in transitional and coastal waters: Proposing metrics for status assessment

In response to the requirements of the Water Framework Directive, a methodology is proposed for assessing the physico-chemical status, specifically nutrient and oxygenation conditions, of the transitional and coastal waters. The method involved several steps: firstly reference conditions were established according to the near-natural reference site criterion and taking into account the main anthropogenic pressures affecting each water body. Secondly, the data were analyzed by bootstrap statistical techniques; the use of percentiles rather than mean values is proposed, in order to minimize the standard sampling error. Finally, the quality ratios for each parameter were calculated taking into account variations in salinity and each status boundary defined as a 50% deviation relative to the next higher class. The final physico-chemical status of each water body was then defined according to the “one out all out” principle. The method was applied to coastal and transitional waters in the central part of the Cantabrian Sea (NW Spain). The results obtained reveal good physico-chemical conditions in most of the water bodies under study, and also indicate strong relationships between the anthropogenic pressures analyzed and the status of each water body.

Estimation of survival quantiles in two-stage randomization designs

In two-stage randomization designs, patients are randomized to one or more available therapies upon entry into the study. Depending on the response to the initial treatment (such as complete remission or shrinkage of tumor), patients are then randomized to receive maintenance treatments to maintain the response or salvage treatment to induce response. One goal of such trials is to compare the combinations of initial and maintenance or salvage therapies in the form of treatment strategies. In cases where the endpoint is defined as overall survival, Lunceford et al. [2002. Estimation of survival distributions of treatment policies in two-stage and randomization designs in clinical trials. Biometrics 58, 48–57] used mean survival time and pointwise survival probability to compare treatment strategies. But, mean survival time or survival probability at a specific time may not be a good summary representative of the overall distribution when the data are skewed or contain influential tail observations. In this article, we propose consistent and asymptotic normal estimators for percentiles of survival curves under various treatment strategies and demonstrate the use of percentiles for comparing treatment strategies. Small sample properties of these estimators are investigated using simulation. We demonstrate our methods by applying them to a leukemia clinical trial data set that motivated this research.

Regional differences in world human body dimensions: the multi-way analysis approach

In the global market, it is vital to design products and work environments to satisfactorily meet the regional variations of human body dimensions. Few studies to date have, however, attempted to examine regional differences due to unavailability of data. Jürgens, H.W., Aune, I.A. and Peiper, U., 1990, International Data on Anthropometry, Occupational Safety and Health Series Report #65 (Geneva: International Labor Office) employed various sources to assemble anthropometric data for 20 world regions. The data provided estimates for the 5th, 50th and 95th percentiles of 19 body dimensions for both genders. In this paper, the method parallel factor analysis (PARAFAC), a natural extension of principal component analysis (PCA) to so-called multi-way array, is performed and favourably compared with the results from PCA. Several comparative studies are performed to justify the use of percentiles rather than individual subject body dimensions. It is found that the outcomes using either are comparable, especially if the body dimensions are mean-centred. Body dimensions related to height (such as stature, buttock–heel length, sitting height and forward reach) are the most critical in describing the international variations; hip breadth showing gender difference is the second most important. People in European regions as well as Australia are the tallest and largest, whereas people in South Indian and Latin American (Indian) regions are the shortest and smallest. The 20 world regions are grouped into four groups that are relatively homogeneous in body dimensions. Potential application of PARAFAC is discussed for the areas in which the data are three-dimensional in nature (such as body dimensions × gender/percentile × age).

Reference Curves for the Gross Motor Function Measure: Percentiles for Clinical Description and Tracking Over Time Among Children With Cerebral Palsy

Physical therapists frequently use the 66-item Gross Motor Function Measure (GMFM-66) with the Gross Motor Function Classification System (GMFCS) to examine gross motor function in children with cerebral palsy (CP). Until now, reference percentiles for this measure were not available. The aim of this study was to improve the clinical utility of this gross motor measure by developing cross-sectional reference percentiles for the GMFM-66 within levels of the GMFCS. A total of 1,940 motor measurements from 650 children with CP were used to develop percentiles. These observations were taken from a subsample, stratified by age and GMFCS, of those in a longitudinal cohort study reported in 2002. A standard LMS (skewness-median-coefficient of variation) method was used to develop cross-sectional reference percentiles. Reference curves were created for the GMFM-66 by age and GMFCS level, plotted at the 3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, and 97th percentiles. The variability of change in children's percentiles over a 1-year interval also was investigated. The reference percentiles extend the clinical utility of the GMFM-66 and GMFCS by providing for appropriate normative interpretation of GMFM-66 scores within GMFCS levels. When interpreting change in percentiles over time, therapists must carefully consider the large variability in change that is typical among children with CP. The use of percentiles should be supplemented by interpretation of the raw scores to understand change in function as well as relative standing.

Distribuição da altura uterina ao longo da gestação em uma coorte brasileira: comparação com a curva de referência do Centro Latino-Americano de Perinatologia

OBJETIVOS: descrever, em gestantes do Estudo Brasileiro do Diabetes Gestacional (EBDG), a distribuicao da altura uterina de acordo com a idade gestacional e validar a curva do Centro Latino-Americano de Perinatologia (CLAP), curva de referencia para a predicao de anormalidades do crescimento fetal. METODOS: o EBDG e uma coorte de 5564 gestantes, com mais de 19 anos, seguidas ate e apos o parto. Entrevistas e medidas antropometricas padronizadas foram feitas no arrolamento entre a 20a e a 28a semana. Os prontuarios foram revisados segundo protocolo padronizado, abrangendo os periodos de pre-natal e parto. As analises referem-se a 3539 gestantes com datacao da gravidez confirmada por ultra-sonografia. Determinamos as propriedades diagnosticas dos percentis 10 e 90 de altura uterina de ambas as curvas (EBDG e CLAP) como indicadores de anormalidade no peso neonatal. RESULTADOS: as medidas de altura uterina no EBDG foram maiores que as do CLAP em todas as semanas de gestacao (1 a 4 cm e 2 a 6 cm, respectivamente, nos percentis 10 e 90). O percentil 10 do CLAP identificou como pequenas as medidas uterinas de 0,3 a 1,7% das gestantes brasileiras, ao passo que o percentil 90 classificou como grandes as medidas uterinas de 42 a 57% das brasileiras. A sensibilidade do percentil 10 do CLAP para predizer recem-nascidos pequenos para a idade gestacional variou de 0,8 a 6% e a especificidade do percentil 90 para predizer grandes para a idade gestacional, de 46 a 61%. CONCLUSOES: a curva de referencia do CLAP nao reflete o padrao de crescimento uterino das gestantes brasileiras, limitando sua capacidade de identificar anormalidades de crescimento fetal, especialmente a restricao de crescimento.

Customized Birthweight Centiles Predict SGA Pregnancies With Perinatal Morbidity

Birth weight traditionally is classified using population-based, sex-adjusted centiles. An infant weighing less than the 10th percentile at birth is considered to be small for gestational age (SGA). Some of these infants, however, are constitutionally small but not growth-restricted. This study was an attempt to reclassify infants using and percentiles, and to compare perinatal morbidity rates in those classified as and those appropriate for gestational age. The cohort study included 374 pregnancies from a general obstetric of 12,879. Pregnancy outcomes were compared for SGA infants who were below the 10th percentile by both and percentiles; SGA only; and SGA only. All pregnancies were evaluated by an ultrasound at less than 20 weeks gestation and by umbilical Doppler study within 2 weeks of delivery. The National Women's Hospital database of births in the years 1993-2000 was used to study the use of percentiles in a general obstetric population. Customized was the birth weight below 10th percentile using the New Zealand percentile calculator. Population was sex-adjusted birth weight less than 10th percentile and was birth weight of 10th percentile or more by both and parameters. At delivery, 80% of infants were by percentiles and 81% were by percentiles. The proportion of infants who were by both these percentiles was 72%. In addition, 7% of infants were customized only, 9% were population only, and 12% were non-SGA both. Mothers of infants who were reclassified as population only had lower body mass indices than those who were SGA both, and they also were likelier to be nulliparous. Women in the customized only group tended to have higher body mass indices. Rates of preeclampsia, abnormal Doppler findings, and cesarean section for fetal distress all were greater in the SGA and customized only groups than in the non-SGA group. These forms of morbidity were similarly frequent in the SGA and customized only groups. Indices of newborn morbidity, including a long hospital stay and composite morbidity, were increased to similar degrees in the SGA and customized only groups. Morbidity was comparatively low in the population only and non-SGA groups. All seven perinatal deaths were in the SGA group. Morbidity risk in babies who were customized only-and who would not have been detected using percentiles-had high morbidity rates comparable to those of infants in the SGA group. Compared with the non-SGA group, relative risk figures for perinatal death were high in the SGA and customized only groups. It appears that the use of birth weight percentiles is able to identify small infants who are at increased risk of perinatal morbidity and mortality.

Body composition measurements: interpretation finally made easy for clinical use.

This review presents the latest clinical applications of bioelectrical impedance analysis. It discusses the evaluation of nutritional status by using fat-free mass and body fat, percentiles of fat-free mass and body fat, height-normalized fat-free mass and body fat mass indices and a resistance/reactance vector graph. Fat-free mass and body fat can be used to evaluate nutritional status by comparing individuals or groups of individuals with themselves or with reference values. Percentile distributions are also useful in determining whether individuals or groups fall within the population range. Percentile ranks can also be used to define nutritional depletion and obesity. The use of the fat-free mass and body fat mass indices has the advantage of compensating for differences in body height. The use of low, normal, high and very high fat-free mass and body fat mass indices ranges that correspond to underweight, normal, overweight and obese body mass index categories further aid in the nutritional assessment process. With vector bioelectrical impedance analysis, an individual impedance vector is compared with the 50, 75, and 95% tolerance ellipses calculated in the reference, healthy population, allowing evaluation in any clinical condition. More accurate estimates of conventional bioelectrical impedance analysis equations might be obtained in individuals with a normal impedance vector. The assessment of fat-free mass and body fat provides valuable information about changes in body composition with weight gain or loss and physical activity, and during ageing. The use of percentiles and height-normalized fat-free mass and body fat permit the classification of patients as under or overnourished.