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PubMed2004

Judging trauma center quality: does it depend on the choice of outcomes?

BACKGROUND: Trauma centers routinely benchmark their survival outcomes against a national norm using the TRISS methodology. However, the use of survival as a measure of the effectiveness of trauma care may be too limited in scope because it fails to capture information regarding functional outcomes. METHODS: The objective of this study was to develop a prediction model that allows hospitals to benchmark their functional outcomes in blunt trauma patients, and to determine whether the assessment of hospital "quality" depends on the choice of outcome measure: survival or survival combined with functional outcome. This retrospective cohort study was based on patients, aged 18 years or older, in the National Trauma Database who sustained blunt trauma in 1999 without associated head or spinal cord injury. We developed a sequential logistic model to predict the probability of a good functional outcome. The TRISS methodology was customized to this data set to obtain a survival model. Using each of these prediction models, we then obtained two standardized measures of hospital performance: one based on the number of survivors and the other based on the number of survivors with good functional outcomes. These standardized outcome measures were then used to identify low-performance and high-performance hospitals. The ranking based on these two different measures were compared. RESULTS: Fifteen of the 27 hospitals in the study cohort were categorized differently when their performance was benchmarked using survival versus functional outcome. Kappa analysis revealed minimal agreement between these two quality measures on the identity of hospital quality outliers (kappa = 0.04; p = 0.35). CONCLUSION: The evaluation of hospital quality depends on whether hospital performance is judged by looking at survival or at survival combined with functional outcome. Because functional status is an important outcome of major concern to survivors, it is important to include it in hospital performance assessment. Consideration should be given to including functional outcome in the evaluation of trauma center performance.

Benchmarking↗
PubMed2004

Change in blood lead concentration up to 1 year after a gunshot wound with a retained bullet.

The authors studied the time course and prevalence of elevated blood lead concentrations and associated injury- and patient-specific factors during the first year following gunshot injury. They determined blood lead levels at mean time points of 0.3, 3.1, 18.7, 94.5, 188.3, and 349.4 days after injury in a volunteer sample of 451 subjects from a Los Angeles, California, trauma center who sustained a first-time gunshot injury with a retained projectile in 2000-2002. In mixed-model analyses, blood lead levels increased with time postinjury (p < 0.0005) up to 3 months, with number of retained fragments (p < 0.0005), and with increasing age (p < 0.0005). Increased blood lead concentration as a function of fragmentation was approximately 30% higher among subjects who had suffered bone fracture in the torso (p < 0.0005). Subjects with bullets or fragments lodged near bone (p < 0.0005) or near joints (p = 0.032) had higher blood lead levels. Logistic models correctly predicted a blood lead elevation of >/=20 micro g/dl in 81% and 85% of subjects at 3 and 6 months postinjury, respectively. The prevalence of elevated blood lead was 11.8% at 3 months and 2.6% at 12 months. The authors recommend continued surveillance of blood lead levels after gunshot injury for patients with key indicators.

Adolescent↗
PubMed1995

Modelling of microbial activity and prediction of shelf life for packed fresh fish.

Prediction of shelf life based on growth of specific spoilage organisms (SSO) in model substrates was studied. The effect of CO2 on the growth kinetics for Photobacterium phosphoreum and Shewanella putrefaciens was quantified and modelled. Results showed that microbial spoilage of packed cod stored with various concentrations of CO2 was accurately predicted from the effect of CO2 on P. phosphoreum grown in model substrates. The short shelf life extensions previously reported for packed cod therefore can be explained by the high CO2 resistance of this Gram negative organism. S. putrefaciens was very sensitive to CO2 and growth rates could not be related to the shelf life of packed cod. Growth curves without lag phases were found for all concentrations of CO2 and for both the microorganisms studied. For the fitting of these growth curves the log-transformed Logistic models were selected after comparison with the 'modified Gompertz' models and with the model of Baranyi et al. (1993). The effect of CO2 on mu max was well described by a 2 parameter square root model. Validation of kinetic models by comparison of shelf life predictions with shelf life determined by sensory evaluations in product experiments was preferred for comparison of microbial growth rates determined in product and model system experiments. Kinetic modelling was found to be valuable for both evaluation and prediction of microbial fish spoilage and an iterative approach for development of kinetic shelf life models was suggested.

Animals↗
PubMed2002

Effect of humic acids on speciation and toxicity of copper to Paracentrotus lividus larvae in seawater.

The effects of humic acid (HA) on the toxicity of copper to sea urchin Paracentrotus lividus larvae were studied in chemically defined seawater. Square Wave Anodic Stripping Voltammetry (SWASV) was employed to study the complexation of copper in seawater medium. A simple complexation model assuming one ligand type and a 1:1 reaction stoichiometry successfully explained the inverse titration experiments. A conditional stability constant of 6.53+/-0.05 and a complexating capacity of 230+/-7 micromol Cu/g HA were obtained. Sea urchin bioassay tests with two endpoints, embryogenesis success and larval growth were carried out in order to study the toxicity of dissolved copper in both the presence and absence of HA. The toxicity data obtained fitted well into a logistic model, and the high sensitivity of both endpoints (EC(50) were 41.1 microg Cu/l and 32.9 microg Cu/l, respectively) encourages their use for biomonitoring. The HA had a clearly protective effect, reducing the toxicity of Cu to the sea urchin larvae. The labile copper, rather than the total copper concentrations, explained the toxicity of the Cu-HA solutions, and the Cu-HA complexes appeared as non-toxic forms. These results are in agreement with the Free Ion Activity Model, because the labile Cu concentrations in this buffered and chemically defined medium covary with the free ion activity of the Cu, validating the model to naturally occurring HA in the marine environment.

Animals↗
PubMed1999

Spatial Scale of Population Synchrony: Environmental Correlation versus Dispersal and Density Regulation.

A stochastic model is developed to analyze the equilibrium spatial pattern of population synchrony, the correlation of temporal fluctuations in population density between localities. The expected population dynamics and the distribution of individual dispersal distance are homogeneous in space. Environmental stochasticity is caused by temporal fluctuations in the intrinsic rate of increase and/or carrying capacity of local populations that are correlated in space (but not time), the environmental correlation decreasing with distance. We analyze a linearized model for small fluctuations. Employing the standard deviation of a function in a given direction as a measure of scale, the spatial scale of population synchrony, lρ, is related to the spatial scales of environmental correlation, le, and individual dispersal, l, by the simple general formula [Formula: see text], where m is the individual dispersal rate and γ is the strength of population density regulation (or rate of return to equilibrium, [Formula: see text] in the logistic model). Relative to environmental correlation (the Moran effect), the contribution of individual dispersal to the spatial scale of synchrony is magnified by the ratio of the individual dispersal rate to the strength of density regulation. Thus, even if the scale of individual dispersal is smaller than that of environmental correlation, dispersal can substantially increase the scale of population synchrony for weakly regulated populations.

Moran effect↗
PubMedDate not supplied

R-NN curves: an intuitive approach to outlier detection using a distance based method.

Libraries of chemical structures are used in a variety of cheminformatics tasks such as virtual screening and QSAR modeling and are generally characterized using molecular descriptors. When working with libraries it is useful to understand the distribution of compounds in the space defined by a set of descriptors. We present a simple approach to the analysis of the spatial distribution of the compounds in a library in general and outlier detection in particular based on counts of neighbors within a series of increasing radii. The resultant curves, termed R-NN curves, appear to follow a logistic model for any given descriptor space, which we justify theoretically for the 2D case. The method can be applied to data sets of arbitrary dimensions. The R-NN curves provide a visual method to easily detect compounds lying in a sparse region of a given descriptor space. We also present a method to numerically characterize the R-NN curves thus allowing identification of outliers in a single plot.

Journal Article↗
PubMed1988

Role of alcohol in cancers of the upper alimentary tract: use of models in risk assessment.

A case-control study of cancers of the upper alimentary tract was conducted in a hospital to assess the role of several risk factors, including alcohol consumption, which is reported here. Male patients from one community with cancers of the oral cavity (n = 278), pharynx (n = 225), and oesophagus (n = 236) formed the case group. Patients diagnosed as not having cancer (n = 215) formed one control group, and a comparable sample of individuals from the general population (n = 177) formed another control group. The risk of regular alcohol consumption along with the two well established risk factors of tobacco smoking and chewing were assessed from the linear logistic model fitted. The process of model fitting has been elaborated. Adjusted odds ratios of alcohol consumption in those under 60 years of age varied from 1.3 to 3.6-fold for developing oral cavity cancer, from 1.9 to 5.4-fold for pharyngeal cancer, and from 1.5 to 2.7-fold for oesophageal cancer, in different age groups. No association was observed between alcohol consumption and cancer in those over 60 years of age. A synergistic effect was observed for the combined habit of alcohol drinking with tobacco smoking and/or chewing. The fact that age is a risk factor independent of habit is also demonstrated.

Adult↗
PubMed2003

[Preliminary study on measurement of human fecundity applicability of time to pregnancy with Japanese subjects].

BACKGROUND: Debate has been continuing whether endocrine disrupting chemicals (EDC) in the environment affect human reproduction. We are planning to use time to pregnancy (TTP) as a measure of human fecundity to relate EDC exposure in a future research. TTP is expressed as the number of non-contracepting menstrual cycles or months required for a couple to conceive. An extended TTP might be considered to reflect an injury to reproductive processes. Since this parameter has never been measured in Japan. the present preliminary study aimed at establishing a Japanese version of the TTP questionnaire and determining if TTP could be reliably measured in Japan. METHODS: We prepared a self-administered questionnaire that consisted of questions on TTP, sexual life and dietary habits. Women who visited a gynecology clinic in Tokyo for confirmation of pregnancy during the period October 2000 to March 2001 were the subjects asked to fill in the questionnaire. The results were statistically analyzed by chi-square test, t-test and binorminal logistic model after classifying the subjects into two groups: (a) Group I (TTP < or = 6 months; n = 53) (b) Group II (TTP > 6 months; n = 16) RESULTS: Of the 92 women approached, 69 (75.0%) could report TTP. The distribution of TTP, the mode being around 1-2 months with a positive skew toward longer value, was similar to those reported so far in Western countries. There were statistically significantly more smokers in Group II (smoker 62.5%) than in I (15.6%). Logistic regression analysis indicated prior gravidity and fish and milk consumption, in addition to cigarette smoking, to be related to TTP. CONCLUSIONS: The present preliminary study indicated that TTP surveys are feasible with Japanese based on the high response rate and plausible distribution of reported value. It also indicated that TTP was related to cigarette smoking, gravidity and dietary habits, again consistent with previous studies.

Adult↗
PubMed1991

Quality of laboratory performance in testing for human immunodeficiency virus type 1 antibody. Variables associated in multivariate analyses.

In May 1988, the Centers for Disease Control's Model Performance Evaluation Program (Atlanta, Ga) surveyed 1092 laboratories that performed enzyme immunoassays and Western blot tests for human immunodeficiency virus type 1 antibody on mailed plasma samples of known human immunodeficiency virus type 1 antibody reactivity and that described their laboratory characteristics and testing practices. The study objective was to evaluate the quality of laboratory performance in testing for human immunodeficiency virus type 1 antibody. After identifying relevant variables in univariate analyses, multivariate analyses were performed using stepwise logistic models. Human immunodeficiency virus type 1 antibody test performance was independently associated with analytic variables such as commercial test kit used and with nonanalytic variables such as experience, training, and degree requirements of laboratory personnel. These results validate the importance of nonanalytic variables to the quality of outcomes in laboratory testing.

AIDS Serodiagnosis↗
PubMed2003

A climate-based model predicts the spatial distribution of the Lyme disease vector Ixodes scapularis in the United States.

An understanding of the spatial distribution of the black-legged tick, Ixodes scapularis, is a fundamental component in assessing human risk for Lyme disease in much of the United States. Although a county-level vector distribution map exists for the United States, its accuracy is limited by arbitrary categories of its reported presence. It is unknown whether reported positive areas can support established populations and whether negative areas are suitable for established populations. The steadily increasing range of I. scapularis in the United States suggests that all suitable habitats are not currently occupied. Therefore, we developed a spatially predictive logistic model for I. scapularis in the 48 conterminous states to improve the previous vector distribution map. We used ground-observed environmental data to predict the probability of established I. scapularis populations. The autologistic analysis showed that maximum, minimum, and mean temperatures as well as vapor pressure significantly contribute to population maintenance with an accuracy of 95% (p < 0.0001). A cutoff probability for habitat suitability was assessed by sensitivity analysis and was used to reclassify the previous distribution map. The spatially modeled relationship between I. scapularis presence and large-scale environmental data provides a robust suitability model that reveals essential environmental determinants of habitat suitability, predicts emerging areas of Lyme disease risk, and generates the future pattern of I. scapularis across the United States.

Animals↗
PubMed1994

Italian multicentre study on very low-birth-weight babies. Neonatal mortality and two-year outcome.

The Italian multicentre study on very low-birth-weight babies is the first collaborative project in Italy on the health status of newborns weighing 500-1499 g at birth: 634 such babies were admitted in 1987-88 to eight Italian NICUs; 424 infants survived and were followed until two years of age, corrected for prematurity. Logistic regression analysis of pre-admission risk factors of in-hospital mortality identified eight statistically significant variables: birth weight, gestational age, sex, antepartum steroids, 1-min Apgar score and, on admission to the NICU, body temperature, pH and absence of spontaneous respiration. Using the equation derived from the logistic model, a theoretical mortality rate was calculated for each centre, predicted on the basis of the local incidence of preadmission risk factors. In no case was the predicted mortality significantly different from the observed one. At two years of age, 8 children were blind and 48 had motor disability. Of these, 46 had cerebral palsy: based on a functional evaluation score 14 had severe (degree 4), 20 intermediate (degree 3) and 12 mild cerebral palsy (degree 2). Among 25 variables entered in a logistic regression as risk factors for cerebral palsy, only periventricular leukomalacia and acidosis were significantly associated with the outcome.

Apgar Score↗
PubMedDate not supplied

Predicting factors for survival of patients with unresectable pancreatic cancer: a management guideline.

BACKGROUND/AIMS: When pancreatic cancer cannot be resected, palliative procedures including gastroenteric bypass and biliary bypass may be selected. However, since predicting survival is difficult, indication of these procedures remains unclear. This study was designed to elucidate the prognostic factors of patients with unresectable pancreatic cancer in order to improve their quality of life. METHODOLOGY: We treated 187 consecutive patients with unresectable pancreatic cancer at the Kobe University Hospital. Fifteen prognostic variables for survival were analyzed (sex, age, the degree of pain, diet, presence of jaundice, main site of the tumor, tumor size, major vessel invasion, liver metastasis, peritoneal dissemination, distal metastasis and operative procedures) in surgically treated patients (n = 125). All patients were followed until death. Cox's proportional hazard model and logistic regression models were used to determine the factors influencing the survival of patients with unresectable pancreatic cancer. RESULTS: Cox's proportional hazard model revealed that duodenal invasion (p = 0.001) and liver metastasis (p < 0.0001) significantly influenced the survival of the patients with unresectable pancreatic cancer. In multivariate logistic regression analysis, liver metastasis (p = 0.009) and peritoneal dissemination (p = 0.004) were significant factors on the six-month survival after palliative operation. CONCLUSIONS: Liver metastasis and peritoneal dissemination were negative predictive factors for the six-month survival of patients with unresectable pancreatic cancer. Palliative bypass surgery is recommended for patients expected to survive long-term (more than six-months).

Adolescent↗
PubMed2000

Angiotensinogen and angiotensin converting enzyme gene polymorphisms and the risk of bipolar affective disorder in humans.

A possible participation of the renin-angiotensin system (RAS) components with mood disturbances has been suggested in both animal and pharmacological models. In this cross-sectional study, we examined the association between functional polymorphisms in the angiotensin converting enzyme (ACE) and angiotensinogen (AGT) genes in 115 bipolar affective disorder (BPAD) patients and 323healthy control subjects. The ACE I/D variant did not show any difference in allelic frequencies and genotypic distribution between the groups. In contrast, when studying the AGT M235T polymorphism we found that the M allele was more frequently observed in BPAD patients than in controls (chi(2)=6.766, d.f.=1, P=0.009). Using multivariate logistic models the strongest odds ratio resulted from a dominant genetic model (OR=3.0; CI (95%) 1.7-5.3] Our data suggest an association between the AGT M235 genotype and increased susceptibility for BPAD in these Brazilian patients. These findings are consistent with the hypothesis that the RAS system plays a role in regulating the mood

Adolescent↗
PubMed1980

Radioimmunoassay data processing with a small programmable calculator.

We have developed three programs for data processing for radioimmunoassays RIA implemented on a small, inexpensive, programmable calculator (Texas Instrument Co., Model 59): 1) The first program performs a weighted logit-log regression for analysis of the RIA standard curve, and provides several descriptive statistics: slope, intercept, ED50 (and their corresponding standard errors), residual variance, and correlation coefficient. This program also provides: dose interpolation for unknowns; an estimate of the precision (percent coefficient of variation) for each result; corrections for variable sample volumes or recoveries; and the mean and standard error of the mean for samples analyzed in replicate. 2) The second program uses the "four parameter logistic model" to describe the dose responses curve and perform dose interpolation. This is the equivalent to the use of the logit-log method, with provision for adjustment for the position of the 0% and 100% response. As such, it is more flexible and versatile than the logit-log method. 3) A third program is used for routine Within-Lab Quality Control: it calculates within-assay and between-assay precision, utilizing an analysis of variance (ANOVA) with a components of variance estimation. These programs incorporate the most important features of programs previously developed in this laboratory for an IBM 370 or a DECsystem-10 computer, and demonstrate the availability of adequate statistical analyses to laboratories without access to large centralized computer facilities.

Analysis of Variance↗
PubMed1989

Logistic and Poisson models for infection by multicomponent plant viruses.

A model for the relationship between virus concentration and infectivity of multicomponent plant viruses is based on a combination of logistic and Poisson equations. Two separate equations are derived from the Poisson distribution assuming, (i) that infections occur only when a set of components containing the complete multicomponent genome is established at an infection site, but that any excess of components present does not reduce the probability of infection (no interference postulate); and (ii) that infection can occur only if a set of components containing the full genome reaches an infection site before it can be preempted by an incomplete set (competitive interference postulate). Postulate (i) affects the form of a dilution series without affecting N, the maximum possible number of infections (lesions), and postulate (ii) changes the value of N but not the form of the dilution series. There is a close correlation between the logit slope of a logistic dilution series and the form of the corresponding multiple Poisson dilution series for viruses with 2, 3 or 4 components. Calibrated by Poisson equations, the logit slope may thus suggest whether or not the virus components have invaded independently and infected similar infection sites. The methods of fitting the combined logistic-Poisson model are demonstrated by applying it to data for cowpea chlorotic mottle virus.

Models, Theoretical↗
PubMed2003

Risk factors for hip fracture in skilled nursing facilities: who should be evaluated?

This paper aims to identify risk factors for hip fracture in Medicare skilled nursing facility (SNF) residents and to develop a predictive model based on routinely collected administrative data (the Minimum Data Set, MDS) to identify high-risk residents. Prospective cohort study of 28,807 North Carolina Medicare SNF residents aged >65 years with a complete MDS assessment in 1999. Demographic, historical, physical, cognitive, behavioral, activities of daily living, and medication variables were obtained from the MDS. Hip fracture occurring after the first MDS assessment identified by ICD-9 code was the outcome measure. Variables significantly associated with hip fracture by chi-square test in a randomly selected derivation sample were combined in a multivariable logistic model and in models stratified by gender. The models were validated in the remaining subjects. Variables significantly related to subsequent hip fracture in the full cohort include: female sex (odds ratio 1.3, 95% confidence interval 1.0-1.7), white race (2.3, 1.6-3.5), age (1.03 per year, 1.01-1.04), cognitive impairment (1.4, 1.8-1.8), incontinence (0.68, 0.5-0.9), prior fractures (1.6, 1.2-2.1), and prior falls (1.4, 1.2-1.8). In ambulatory non-Hispanic white women, anxiety (1.5, 1.0-2.1), anxiolytic use (1.4, 1.1-1.9), wandering (1.4, 1.0-2.2), and training in community skills (1.4, 1.1-1.8) were new significant variables. For ambulatory non-Hispanic white men, education level (2.0, 1.2-3.2), weight loss (0.5, 0.2-1.0), history of osteoporosis (3.0, 1.3-6.7), pathologic bone fracture (9.7, 2.2-42.6), COPD (2.1, 1.3-3.5), glaucoma (2.6, 1.0-6.2), and standing balance impairment (1.8, 1.0-3.3) were also significant. All models were highly correlated with subsequent hip fracture, but the discriminative ability was limited (c statistic 0.678). Risk factors explained more of hip fracture risk in non-Hispanic white men (c statistic 0.793) than non-Hispanic white women (0.658). Risk factors for hip fracture in Medicare SNF residents have similarities and differences from those previously identified in community-dwelling older adults. Osteoporosis screening and intervention should focus on the healthiest, most independent subset of residents who have the greatest fracture risk.

Activities of Daily Living↗
PubMed1978

[Determining the average posteruptive age of teeth from the results of cross-sectional studies (author's transl)].

If results of cross-sectional studies must be used as a basis for setting up models of development of caries in permanent teeth, then the average rather than individual posteruptive age of teeth has to be resorted to. Data available for this purpose had been obtained from a total of 54,000 children living in two G.D.R. cities, namely, Plauen and Karl-Marx-Stadt, as well as from two surveys made in 1959 and 1971, respectively. Calculation of the average posteruptive age of teeth assumes good knowledge of the distribution of dates of eruption in a population. Of the three types of distribution considered, namely, normal, lognormal, and log-logistic distribution, the log-logistic model proved to be superior to others because of better adaptation to the data available. The method of calculating the posteruptive age of teeth is described and illustrated by use of a number of examples. Since one of the two surveys (namely that which was made in Karl-Marx-Stadt in 1971) was made after twelve years' drinking water fluoridation, it was possible to study the effect of fluoridation upon the eruptive behavior of permanent teeth. The results of this study confirmed those obtained during previous investigations.

Adolescent↗
PubMed1996

Outcome of neurological decompression illness: development of a manifestation-based model.

A significant proportion neurological decompression illness cases remain symptomatic after the first recompression treatment. Currently, the factors that predict an incomplete resolution are poorly defined. In this study, 214 cases of neurological decompression illness were reviewed and classified according to the presenting manifestations and outcome after a standard therapeutic regimen. The neurological manifestations were classified by type (loss of sensory or motor function, or loss of consciousness) and then by either the number of sites involved or the location of each manifestation. Cases with both sensory and motor manifestations were less likely to have complete resolution than those with sensory or motor manifestations alone. Cases with manifestations involving the legs were less likely resolve completely than those with manifestations in the arms, especially if both sensory and motor manifestations were reported. Based on these data, a linear logistic model was developed to predict the probability of incomplete resolution after the first recompression treatment depending on the type and location of the manifestations.

Adolescent↗