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PubMed1990

The visual pathways of eutherian mammals and marsupials develop according to a common timetable.

Data from cats, ferrets, hamsters, macaques, mice, rabbits and rats concerning the time of occurrence of 26 developmental events involved in the establishment of the retinofugal, geniculocortical, corticogeniculate and corticocollicular pathways were analysed. For each species the timing of developmental events was expressed as a proportion of the period between conception and eye opening ('caecal period'). For 6 of these events, the values for all species fell within a range of 1-5% of the caecal period, the values for 11 other events fell within a range of 6-10% of the caecal period, 4 events had ranges of 11-15% of the caecal period, and only 5 events were spread over more than 15% of the caecal period. The 26 events had an overall mean variation of about 11% of the caecal period, suggesting that the visual pathways of eutherian mammals develop according to a common 'timetable' that is related to the duration of the caecal period. One of the roles of this common timetable may be to assist the establishment of orderly interconnections between the visual centres. Relatively few data are available concerning the timing of developmental events in marsupial visual pathways. However, it is apparent that, during the first half of the caecal period, most events occur much earlier in marsupials than in eutherians, whereas during the second half of the caecal period most events occur at the same stages of the caecal period in both marsupials and eutherians. The accelerated rate of visual development during the first half of the caecal period in marsupials may be related to the precocious development that they undergo prior to their very early birth.

Animals↗

PubMed2002

Bolbophorus damnificus n. sp. (Digenea: Bolbophoridae) from the channel catfish Ictalurus punctatus and American white pelican Pelecanus erythrorhynchos in the USA based on life-cycle and molecular data.

The common pathogenic prodiplostomulum metacercaria in the flesh, mostly near the skin, of pond-produced channel catfish Ictalurus punctatus has been demonstrated to be Bolbophorus damnificus Overstreet & Curran n. sp. The catfish acquires the infection from the snail Planorbella trivolvis, the only known first intermediate host, and the species is perpetuated through the American white pelican Pelecanus erythrorhynchos, as confirmed by experimental infections with nestling and dewormed adult pelican specimens in conjunction with molecular data. It differs from the cryptic species Bolbophorus sp., also found concurrently in the American white pelican, by having eggs 123-129 microm rather than 100-112 microm long and consistent low values for nucleotide percentage sequence similarity comparing COI, ITS 1/2, 18S rRNA and 28S rRNA fragments. Bolbophorus sp. is comparable but most likely distinct from B. confusus (Kraus, 1914), which occurs in Europe and has eggs 90-102 microm long. Its intermediate hosts were not demonstrated. The adults of neither of the confirmed North American species of Bolbophorus were encountered in any bird other than a pelican, although several shore birds feed on infected catfish, and B. damnificus can survive but not mature when protected in the mouse abdominal cavity. B. ictaluri (Haderlie, 1953) Overstreet & Curran n. comb., a species different from B. damnificus, is considered a species inquirenda.

Animals↗

PubMed2001

Power of regression and maximum likelihood methods to map QTL from sib-pair and DZ twin data.

A common study design to map quantitative trait loci (QTL) is to compare the phenotypes and marker genotypes of two or more siblings in a sample of unrelated sib groups, and to test for linkage between chromosome location and quantitative trait values. The simplest case is sib pairs only, in particular dizygotic twin pairs, and a simple and elegant regression method was proposed by Haseman & Elston in 1972 to test for linkage. Since then, several other methods have been proposed to test for linkage. In this study, we derived the statistical power of linear regression and maximum likelihood methods to map QTL from sib pair data analytically, and determined which methods are superior under which set of population parameters. In particular, we considered four regression-based and three maximum likelihood-based approaches, and derived asymptotic approximations of the mean test statistic and statistical power for each method. It was found, both analytically and by computer simulation, that the revisited or new Haseman-Elston method (based upon the mean-corrected crossproduct of the observations on sib-pairs) is less powerful than a full maximum likelihood approach and is also inferior to the Haseman-Elston method under a realistic range of values for the population parameters. We found that a simple regression method, based upon both the squared difference and the mean-corrected squared sum of the observations on sib-pairs, is as powerful as a full maximum likelihood approach. Our derivations of statistical power for regression and maximum likelihood methods provide a simple way to compare alternative methods and obviate the need to perform elaborate computer simulations. DZ twin pairs are likely to be more powerful for linkage analysis than ordinary siblings because they may share more common environmental effects, thereby increasing the proportion of within-family variance that is explained by a QTL.

Chromosome Mapping↗

PubMed2005

Linear signed-rank tests for paired survival data subject to a common censoring time.

In this paper we consider rank-based tests for paired survival data, in which pair members are subject to the same right censoring time. Linear signed-rank tests have already been developed for the two-treatment problem in which pair members receive the opposite treatments. Assuming a bivariate accelerated failure time model, we extend this class of linear signed-rank tests to the case of multiple covariates, making this methodology applicable to more complicated experimental designs. These tests can be reformulated as weighted sums of contigency table measures, giving an alternative method of computation and intuitive view of how these tests work. A simulation study of their small-sample performance relative to other tests demonstrates that the linear signed-rank tests have greater power in cases of moderately to highly correlated data.

Humans↗

PubMed1995

Toxicological potency of 2,3,7,8-tetrachlorodibenzo-p-dioxin relative to 100 other compounds: a relative potency analysis of in vitro and in vivo test data.

A common definition of relative potency is the dose of a reference compound required to cause a particular incidence of a specific toxic response divided by the dose of a test compound needed to cause an equal incidence of that same effect. In this simple manner, toxicological assessments for a chemical of concern can be made in terms of another compound about which much is known from a human health perspective. Relative potency factors were used to compare 2,3,7,8-tetrachlorodibenzo-p-dioxin CAS # 1746-01-6 (TCDD) with 100 other compounds both individually and collectively. All results were standardized to a common scale that spanned many orders of magnitude and was indexed to an arbitrary potency of unity for benzo(a)pyrene [B(a)P]. From comparisons between 2,771 pairs of bioassay results (i.e., matched experimental design conditions) for TCDD compared with the 100 other compounds, it was found that TCDD is about 600 times as toxic as B(a)P (interquartile range of 130 to 1,900). The distribution of relative potency values is fitted accurately with a log-normal distribution function having an untransformed mean of 550 and an untransformed slope (i.e., the inverse of the standard deviation of the distribution) of 140. These factors combined with (a) a reference lifetime carcinogenic risk level of 1/100,000 and (b) a universal, potency-dependent risk coefficient (estimated from the collection of epidemiologically-based carcinogens) yielded estimates that equally toxic concentrations for TCDD should be in the range of 13 pg/m3 and 7 pg/L in air and water, respectively.

Animals↗

PubMed1998

[Cerebral ischemic disorders in the young subject. Epidemiologic and prognostic data].

A COMMON EVENT: Cerebral vascular events in young subjects account for 5 to 15% of all such cases admitted to specialized services. The incidence of cerebral vascular events in young subjects varies from 3 to 40 per 100,000 depending on the study period (incomplete explorations in early studies), the study site (industrialized or developing country) and the ethnic background of the population. A HETEROGENEOUS GROUP: Although cerebral vascular events are defined as those occurring in subjects aged 18 to 45 years, the population is nevertheless quite heterogeneous due to rising incidence after 35 years and variable frequency of age-dependent and site-dependent underlying causes. RELATIVELY GOOD PROGNOSIS: Early mortality is relatively low (approximately 5%) and two-thirds of the subjects suffer minor or mild sequellae. However, depression, which is frequent, and the impossibility to return to normal work activities have an important impact on quality of life.

Adult↗

PubMed2001

Sample size and power calculations with correlated binary data.

Correlated binary data are common in biomedical studies. Such data can be analyzed using Liang and Zeger's generalized estimating equations (GEE) approach. An attractive point of the GEE approach is that one can use a misspecified working correlation matrix, such as the working independence model (i.e., the identity matrix), and draw (asymptotically) valid statistical inference by using the so-called robust or sandwich variance estimator. In this article we derive some explicit formulas for sample size and power calculations under various common situations. The given formulas are based on using the robust variance estimator in GEE. We believe that these formulas will facilitate the practice in planning two-arm clinical trials with correlated binary outcome data.

Clinical Trials as Topic↗

PubMed2005

Missing data: an introductory conceptual overview for the novice researcher.

Missing data is a common issue in research that, if improperly handled, can lead to inaccurate conclusions about populations. A variety of statistical techniques are available to treat missing data. Some of these are simple while others are conceptually and mathematically complex. The purpose of this paper is to provide the novice researcher with an introductory conceptual overview of the issue of missing data. The authors discuss patterns of missing data, common missing-data handling techniques, and issues associated with missing data. Techniques discussed include listwise deletion, pairwise deletion, case mean substitution, sample mean substitution, group mean substitution, regression imputation, and estimation maximization.

Algorithms↗

PubMed1997

Computerized patient record: are we prepared for our future practice?

OBJECTIVE: To survey members of The American Dietetic Association (ADA) regarding care documentation systems, computerization of patient care records, and factors to be considered in developing a documentation system compatible with a computer-based patient record. DESIGN: The survey instrument was developed in conjunction with a survey consultant/statistician, then mailed to the study sample. SUBJECTS/SETTING: The sample of 500 was drawn from three ADA dietetic practice groups expected to include a high percentage of clinical practitioners. STATISTICAL ANALYSIS PERFORMED: Basic frequency displays were used on all questionnaire items. Pearson correlation coefficients were used among numeric variables, and oneway analysis of variance was used for categoric variables with quantitative variables. RESULTS: A total of 171 usable surveys were returned (34%), primarily from dietitians working in an acute-care inpatient environment. The SOAP format (subjective, objective, assessment, and plan) was used by 60% of respondents to document nutrition assessments, although a number of other documentation formats were reported. Most commonly used data in nutrition decision making were medical diagnosis, diet order, anthropometric data, and laboratory values. Most commonly used outcomes measures included laboratory values, tolerance of the nutrition regimen, weight changes, and intake changes. Only 15% of respondents reported that they currently used a computerized patient record. Ninety-three percent of respondents favored standardized nutrition diagnoses, and 95% believed standardized nutrition interventions would prove useful. APPLICATIONS/CONCLUSIONS: We recommend that dietitians evaluate, standardize, and streamline their documentation to prepare for implementation of computerized systems. The diagnoses and interventions presented in this study could be a starting point.

Data Collection↗

PubMed2007

Virtual spatial registration of stand-alone fNIRS data to MNI space.

The registration of functional brain data to common stereotaxic brain space facilitates data sharing and integration across different subjects, studies, and even imaging modalities. Thus, we previously described a method for the probabilistic registration of functional near-infrared spectroscopy (fNIRS) data onto Montreal Neurological Institute (MNI) coordinate space that can be used even when magnetic resonance images of the subjects are not available. This method, however, requires the careful measurement of scalp landmarks and fNIRS optode positions using a 3D-digitizer. Here we present a novel registration method, based on simulations in place of physical measurements for optode positioning. First, we constructed a holder deformation algorithm and examined its validity by comparing virtual and actual deformation of holders on spherical phantoms and real head surfaces. The discrepancies were negligible. Next, we registered virtual holders on synthetic heads and brains that represent size and shape variations among the population. The registered positions were normalized to MNI space. By repeating this process across synthetic heads and brains, we statistically estimated the most probable MNI coordinate values, and clarified errors, which were in the order of several millimeters across the scalp, associated with this estimation. In essence, the current method allowed the spatial registration of completely stand-alone fNIRS data onto MNI space without the use of supplementary measurements. This method will not only provide a practical solution to the spatial registration issues in fNIRS studies, but will also enhance cross-modal communications within the neuroimaging community.

Adult↗

PubMed1999

Member risk adjustment for ambulatory episodes of care.

The purpose of this study was to model health-plan member risk based on member characteristics in order to separate member risk from other utilization determinants for the use of health care services across sites of care. The approach was to build episodes of care (EOCs) by sorting one year of encounter/claims data into Common Treatment Categories (CTCs). These data came from a variety of health plans, both capitated and non-capitated, covering over 2 million lives. The EOCs were characterized by an array of event and intensity measures. Episode-level risk for each of these measures was modeled by regressions based on member demographic and clinical characteristics. The results of this study show that member characteristics explain a substantial amount of event and intensity variation within episodes and that no single performance measure can summarize the care of health plan members. This method for evaluating member risk can be used both to stratify members according to their future risk and potentially to assess provider or health plan performance or to adjust reimbursement for performance or risk selection.

Adult↗

PubMed2005

The influence of common area lead hazards and lead hazard control on dust lead loadings in multiunit buildings.

Owners of multiunit buildings built before 1978 that have interior common areas, and who receive certain forms of federal assistance are generally required to address lead-based paint hazards in those common areas. This study examines the relationships between common area paint and dust lead levels and the floor dust lead loadings in associated dwelling units, as well as the effects of lead hazard control treatments in common areas. This article presents data from common areas in 145 low-income, mostly pre-1940, multiunit buildings with 342 associated dwellings in the U.S. Department of Housing and Urban Development Lead Hazard Control Grant Program at preintervention, clearance, and 1-year postintervention. Interior common areas in these multiunit buildings were not as well maintained as the dwellings in the buildings. At preintervention, a higher percent of the interior common areas had non-intact, lead-based paint on windows, doors and trim, and other interior components than in associated dwellings (95% versus 85%; 78% versus 67%; and 85% versus 62%). Common areas had preintervention entry and interior (i.e., nonentry) floor dust lead loadings more than four times higher than in dwelling units (128 versus 30 micro g/ft(2); 130 versus 28 micro g/ft(2)) while 1-year postintervention common area dust lead loadings are four to six times that of dwelling dust lead loadings (41 versus 11 micro g/ft(2); 44 versus 8 micro g/ft(2)). Windowsill dust lead loadings in common areas were twice the loadings in dwelling units at preintervention and 1-year postintervention (756 versus 383 mu g/ft(2); 154 versus 68 micro g/ft(2)). Interior common area treatments reduced geometric mean common entry dust lead loadings 71% from preintervention to clearance, and maintained those reduced levels from clearance to 1-year postintervention. Higher level interventions were not more effective than low-level interventions in reducing preintervention levels to clearance or 1-year postintervention. This study demonstrates that interior common areas in the multiunit buildings examined contain substantial amounts of deteriorated lead-based paint and dust. Remediation of common areas can effectively reduce those hazards.

Air Pollution, Indoor↗

PubMed2006

Primary hypertension and nephropathy.

PURPOSE OF REVIEW: The relationship between primary hypertension (formerly called essential hypertension) and hypertension-associated chronic kidney disease is complex and poorly understood. The strong association between hypertension-associated chronic kidney disease and cardiovascular disease supports the existence of common mediators. We will review data indicating common mediating mechanisms for cardiovascular disease and chronic kidney disease in primary hypertension. RECENT FINDINGS: Chronic kidney disease develops in primary hypertension due to local and systemic inflammatory mediators that cause endothelial injury. This injury is an important early step in the development of hypertension-associated vasculopathy that causes nephron ischemia with nephrosclerosis. Similar mechanisms mediate endothelial injury in cardiovascular disease and its progression. Subjects with primary hypertension at increased risk for chronic kidney disease are at higher risk for cardiovascular disease, the major cause of mortality in primary hypertension. SUMMARY: Primary hypertension is a modifiable risk factor for both cardiovascular disease and chronic kidney disease. Better understanding of how primary hypertension leads to these outcomes might help in the development of pharmacologic strategies that retard and/or prevent chronic kidney disease in primary hypertension. Because of the strong association between cardiovascular disease and chronic kidney disease in primary hypertension, this improved understanding will likely lead to better therapies to hinder the development and/or progression of cardiovascular disease, in addition to its benefits in preventing hypertension-associated chronic kidney disease.

Albuminuria↗

PubMed2006

A simple local sensitivity analysis tool for nonignorable coarsening: application to dependent censoring.

Right- and interval-censored data are common special cases of coarsened data (Heitjan and Rubin, 1991, Annals of Statistics19, 2244-2253). As with missing data, standard statistical methods that ignore the random nature of the coarsening mechanism may lead to incorrect inferences. We extend a simple sensitivity analysis tool, the index of local sensitivity to nonignorability (Troxel, Ma, and Heitjan, 2004, Statistica Sinica14, 1221-1237), to the evaluation of nonignorability of the coarsening process in the general coarse-data model. By converting this index into a simple graphical display one can easily assess the sensitivity of key inferences to nonignorable coarsening. We illustrate the validity of the method with a simulated example, and apply it to right-censored data from an observational study of cardiac transplantation and to interval-censored data on time to detectable viral load from a clinical trial in HIV disease.

Biometry↗

PubMed1998

Validity of the Department of Defense Standard Inpatient Data Record for quality management and health services research.

OBJECTIVE: To assess the validity of the Department of Defense's Standard Inpatient Data Record (SIDR) for health services research and quality measurement. SUBJECTS: Patients whose inpatient charts were abstracted through the Civilian External Peer Review Program's studies of acute myocardial infarction (N = 1,432) and 1993 review of the birth product line (N = 9,705). METHODS: Separate databases of professionally abstracted (the clinical data set) and hospital-reported (the administrative SIDR data set) diagnoses and procedures were compared for each patient, and the sensitivity and specificity of the SIDR for elements in the Civilian External Peer Review Program's clinical "gold standard" data set were calculated. Agreement beyond chance was examined with kappa statistics. RESULTS: The clinical data set's principal procedure was found as a SIDR principal or secondary procedure in 92.5% of cases. Sensitivities of the SIDR data for common diagnoses in the clinical data ranged from 64% (viral infection) to 97% (diabetes), with kappa statistics ranging from 0.55 to 0.96. Procedural sensitivities ranged from 77% (echocardiography) to 99% (cesarean section), with kappa statistics ranging from 0.7 to 1.0. CONCLUSIONS: Our analyses indicate that the Department of Defense's SIDR is a reliable source of administrative data that compares favorably with traditional civilian quality management and health services research data sources, such as those from the Health Care Financing Administration and large insurers.

Female↗

PubMed1981

Consistency of data collected from inmates of a common lodging house.

The quality of data obtainable by questionnaire from residents of a common lodging house was explored by comparing the answers received by questioning such men on two or three occasions six months apart. Consistency between the answers obtained on different occasions was good for men who already knew the interviewer well as their medical officer but poor otherwise.

Data Collection↗

PubMed1991

Tricuspid atresia or severe stenosis with partial common atrioventricular canal: anatomic data, clinical profile and surgical considerations.

The anatomic findings in 11 cases of tricuspid atresia and in two cases of severe tricuspid stenosis, both combined with partial common atrioventricular (AV) canal, are presented in detail. Twelve cases were documented by postmortem examination and the diagnosis was confirmed by echocardiography and surgical observation in the one living patient. Clinical data available in nine cases and cardiac catheterization data obtained in eight are included in this report. In three cases (23%)--two with tricuspid atresia and one with extreme tricuspid stenosis--the tricuspid valve and right ventricle exhibited characteristics seen in Ebstein's anomaly. In all 13 cases, the great arteries were normally related. The ventricular septal defect(s) in 10 (83%) of the 12 postmortem cases rapidly became smaller and this resulted in marked diminution of the pulmonary blood flow and severe hypoxia. Only three of the eight patients with available cardiac catheterization and angiocardiographic data showed the scooped-out appearance of the left ventricular septal surface characteristic of AV canal defects. By contrast, two-dimensional echocardiography, available in the three most recent cases, accurately demonstrated all the defects present and represents the diagnostic method of choice. Early surgical intervention to establish a systemic to pulmonary artery anastomosis is essential for survival. More definitive surgical treatment can be achieved later by an atriopulmonary or cavopulmonary anastomosis with or without replacement of the cleft and often regurgitant mitral valve. The one living patient exemplifies this approach. This is the largest series of this unusual type of tricuspid atresia reported to date.

Cardiac Catheterization↗

PubMed2001

Natural agents in the prevention of cancer, part two: preclinical data and chemoprevention for common cancers.

This paper is the second of a series examining the use of nutritional supplements as chemopreventive agents. The animal and in vitro data are reviewed in support of their use. Human safety data and mechanisms of action are described as well. Many over-the-counter dietary supplements have been shown to have significant chemopreventive activity in preclinical studies. Few side effects are associated with even long-term use of these agents. Along with dietary and lifestyle risk-reducing strategies, nutritional supplementation appears to be a viable intervention for those considered to be at high risk of developing cancer.

Animals↗