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PubMedDate not supplied

Evaluation of impedance cardiography: comparison of NCCOM3-R7 with Fick and thermodilution methods.

OBJECTIVE: To assess the degree of error of the BoMed NCCOM3 model revision seven (R7) impedance cardiograph in determining stroke volume and estimated cardiac output. DESIGN: Three-group, within-subject, repeated measures design. SAMPLE: Group 1: patients (n = 17) with heart disease undergoing an elective coronary angiogram; group 2: patients (n = 28) after elective heart surgery; and group 3: healthy volunteers (n = 28). MEASUREMENT: Cardiac output was determined by the BoMed NCCOM3-R7 impedance cardiograph, Fick principle, and thermodilution method. The NCCOM3-R7 was compared with the direct Fick and thermodilution methods in groups 1 and 2, respectively, to estimate validity coefficients. In group 3, repeated measures were obtained with the NCCOM3-R7 to calculate reliability coefficients. RESULTS: The NCCOM3-R7 underestimated Fick measurements by 1.050 +/- 1.529 L/min at rest and 1.505 +/- 2.214 L/min during exercise. Correlation coefficients of 0.684 at rest (p = 0.001) and 0.219 during exercise (p = 0.248) were obtained. The NCCOM3-R7 underestimated thermodilution values by 0.425 +/- 1.325 L/min in subjects initially after heart surgery and 0.358 +/- 1.235 L/min 2 to 4 hours later. Correlation coefficients of 0.547 (p = 0.002) and 0.505 (p = 0.004) were obtained for the two time periods, respectively. A reliability coefficient of 0.837 was calculated with healthy subjects. CONCLUSION: The NCCOM3-R7 has a clinically unacceptable level of error for evaluating cardiac performance in patients with heart disease.

Adult↗
PubMed2002

Investigation of trace element sources from an industrialized area (Avilés, northern Spain) using multivariate statistical methods.

In the industrialized urban area of Avilés (Spain), pooled soil samples from grassland sites were taken after careful sampling design and then investigated for their content of trace elements. A combination of statistic and geostatistic techniques proved to be a reliable tool in the interpretation of the analytical results. Geochemical groups and areas influenced mainly by anthropogenic activities were distinguished by means of classic multivariate methods (factor analysis and cluster analysis) and innovative geostatistical tools (Fourier spectral analysis). The constitution of the groups is supported by the linked results of methods sequentially distributed in order to extract as much information as possible from the original data.

Cities↗
PubMed2002

Prevalence and progression of myopic retinopathy in an older population.

OBJECTIVE: To determine the prevalence and progression of myopic retinopathy in an older community-based population sample. DESIGN: Population-based epidemiologic study. PARTICIPANTS: Eligible residents aged 49 years or older (n = 3654) who attended the Blue Mountains Eye Study, west of Sydney, Australia. METHODS: Participants had a detailed eye examination including measurement of logarithm of the minimum angle of resolution (logMAR) visual acuity, standardized refraction, and retinal stereophotography. All patients were invited to attend follow-up examinations after 5 years. MAIN OUTCOME MEASURES: Myopic retinopathy was defined to include staphyloma, lacquer cracks, Fuchs' spot and myopic chorioretinal atrophy. beta-peripapillary atrophy was assessed separately. RESULTS: Signs of myopic retinopathy were found in 67 eyes from 44 participants (1.2%), a prevalence of 1.4% in women and 1.0% in men; this increased from 1% in right eyes with myopia <3 diopters to over 50% in right eyes with myopia > or =9 diopters. There was a nonsignificant age-related trend in prevalence. The average spherical equivalent refraction was -6.1 diopters and the average visual acuity was 20/40 in eyes with myopic retinopathy. Visual impairment (<20/40) was present in 38.8% of affected eyes. Myopic retinopathy was bilateral in 52% of cases. Staphyloma was present in 26 participants (0.7%), bilateral in 35%, with a strong concordance of staphyloma location. Lacquer cracks were seen in 8 participants (0.2%), Fuchs' spot in 3 (0.1%), and chorioretinal atrophy in 7 (0.2%). Forty-six eyes (68.7%) with myopic retinopathy were reexamined after 5 years; 8.7% had new or increased numbers of lacquer cracks and 15.2% had new or expanded areas of chorioretinal atrophy. In those eyes developing lacquer cracks or chorioretinal atrophy, best-corrected visual acuity decreased by a mean of two LogMAR lines. CONCLUSIONS: This study documented the age and sex-specific prevalence of myopic retinopathy and 5-year progression in an older white population.

Age Distribution↗
PubMed2003

Molecular analysis of region t(5;6)(q21;q21) in Wilms tumor.

We have previously described the physical localization of a constitutional t(5;6)(q21;q21) in a patient (tumor cell sample designated as MA214) with bilateral Wilms tumor (WT). We have now physically refined the breakpoints and identified putative gene targets within this region. The translocation breakpoints are contained within a 2.5-Mbp region on 5q21 containing four candidate genes and a 1.3-Mbp region on 6q21 that contains three candidate genes. To explore the role of this region in WT genesis, we have performed loss of heterozygosity (LOH) analysis with markers flanking the translocation breakpoints in tumor from MA214 and a panel of sporadic WT. Alleles were retained for all informative markers used in the MA214 tumor. In sporadic tumors LOH was found in 6 of 63 (9.5%) and 5 of 62 (8%) informative cases for flanking markers D6S301 and D6S1592 on 6q21. LOH was found in 3 of 58 (5.2%) and 2 of 54 (3.6%) for flanking markers D5S495 and D5S409 on 5q21. These preliminary data suggest LOH at the t(5;6)(q21;q21) region is unlikely to be a mechanism for tumor development in MA214, but may be important for a subgroup of sporadic WT.

Chromosomes, Human, Pair 5↗
PubMed2000

Principles and practical application of the receiver-operating characteristic analysis for diagnostic tests.

We review the principles and practical application of receiver-operating characteristic (ROC) analysis for diagnostic tests. ROC analysis can be used for diagnostic tests with outcomes measured on ordinal, interval or ratio scales. The dependence of the diagnostic sensitivity and specificity on the selected cut-off value must be considered for a full test evaluation and for test comparison. All possible combinations of sensitivity and specificity that can be achieved by changing the test's cut-off value can be summarised using a single parameter; the area under the ROC curve. The ROC technique can also be used to optimise cut-off values with regard to a given prevalence in the target population and cost ratio of false-positive and false-negative results. However, plots of optimisation parameters against the selected cut-off value provide a more-direct method for cut-off selection. Candidates for such optimisation parameters are linear combinations of sensitivity and specificity (with weights selected to reflect the decision-making situation), odds ratio, chance-corrected measures of association (e. g. kappa) and likelihood ratios. We discuss some recent developments in ROC analysis, including meta-analysis of diagnostic tests, correlated ROC curves (paired-sample design) and chance- and prevalence-corrected ROC curves.

Animal Diseases↗
PubMed1998

An analysis of mortality in the grower/finisher phase of swine production in the United States.

Over a 6-month period, the mean mortality risk (based on 393 operations participating in the United States National Animal Health Monitoring System 1995 National Swine Study, and representing operations with > or = 300 market hogs in 16 states), was 2.3 +/- 0.2% in the grower/finisher production phase (where figures after the +/- represent the standard error of the estimate). Mortality > or = 4% was experienced by 13.5 +/- 2.9% of grower/finisher operations, while 63.6 +/- 5.3% had < or = 2% mortality. To identify factors associated with > or = 4% mortality, stepwise logistic regression [Statistical Analysis Systems, 1989. SAS/STAT User's Guide, Version 6, 4th edn, Vol. 2. SAS Institute, Cary, NC, 794 pp.] was performed twice: once using operations with all mortality rates, and again excluding operations with between 2% and 4% mortality. Final models were run with SUDAAN [Shah, B.V., Barnwell, B.G., Bieler, G.S., 1996. SUDAAN User's Manual, Version 6.40, 2nd edn. Research Triangle Institute, Research Triangle Park, NC, 492 pp.] to take the sample design into account. In addition, SAS and SUDAAN logistic regression models were developed to analyze factors associated with > 2.3% mortality among grower/finisher pigs. Mean weaning age < or = 28 days entered all models as being associated with increased mortality in the grower/finisher unit. Not obtaining all grower/finisher pigs from farrowing units belonging to the operation was associated with > or = 4% mortality among grower/finisher swine. Not typically giving grower/finisher pigs antibiotics or other agents as disease-preventives or growth-promotants in the feed or water, and ranking producer organizations as very or extremely important sources of antibiotic information were associated with < or = 2.3% mortality in the grower/finisher phase.

Aging↗
PubMed2001

Statistical inference of progressivity dominance: an application to health care financing distributions.

This paper employs a distribution-free statistical test suitable for comparisons based on dependent samples to analyse changes in health care financing distributions on Finnish data. In distinction to the more general summary index approach used in most studies of progressivity measurement, the difference between the Lorenz curve of income inequality and the concentration curves of various taxes and payments is used to evaluate progressivity dominance and changes in progressivity. Sample weights are applied to account for the effect of sampling design and non-response. The analysis demonstrates that the dominance approach can be successfully applied to various types of distributional problems besides comparisons concerning differences in income distributions. As an empirical application the paper presents estimation results for the progressivity of various health care financing sources using data from the 1987 and 1996 Finnish Health Care Surveys.

Family Characteristics↗
PubMed1997

The postimperative negative variation following ambiguous matching of auditory stimuli.

Previous studies using the delayed-matching-to-sample paradigm with visual stimuli reliably induced a postimperative negative variation (PINV) in both schizophrenic patients and healthy controls. The PINV was found to be: (a) larger in schizophrenic patients than controls; (b) larger under conditions of ambiguous as compared to clear matching conditions; and (c) larger over right-hemispheric, fronto-temporal regions in controls, while a less asymmetrical distribution with a tendency for left-frontal predominance occurred in schizophrenic patients. The present study examined to what extent the development and scalp distribution of the PINV were modality-specific by applying the delayed-matching-to-sample design using auditory stimuli. Furthermore, the neurophysiological state during anticipatory negativity (CNV) and PINV was examined by presenting acoustic probe stimuli (one per trial on 50% of the trials) during baseline, CNV or PINV interval. Event-related slow and probe-evoked potentials were recorded in 13 patients with a chronic schizophrenic disorder (DSM-III-R) and 13 healthy control Ss from 15 electrode sites including midline and two sagittal rows over each hemisphere. Comparable group differences and effects of ambiguity on PINV amplitudes were found for both modalities, visual and auditory. The auditory stimuli produced a fronto-central distribution of the PINV in both groups. The probe-evoked vertexpotential was smaller in patients compared to controls, but exhibited comparable modulation with the largest amplitude during the CNV in both groups. Results suggest modality-non-specific cognitive determinants of the PINV. However, stimulus modality did affect the scalp distribution of the PINV. Probe-evoked responses point to different functional meaning of negativities prior to (CNV) and following (PINV) task-relevant stimuli.

Acoustic Stimulation↗
PubMed2002

Model choice in gene mapping: what and why.

The choice of an appropriate genetic model describing the genetic architecture underlying a character of interest is an inherent part of the gene mapping studies of human and other living organisms. The genetic model specifies the statistical parameters for the number of genes, their positions, and the types and magnitudes of their contributions to the phenotype. There are many considerations involved in model formulation (choice) ranging from the assumptions concerning the data, the role of environment, and the number of oligogenes (or quantitative trait loci) influencing the trait behavior. There are several model selection procedures and criteria under specific sampling designs in the genetic literature. These approaches often have their origin in computer science or in general statistical theory. Our aim here is to give an overview of the most popular statistical criteria and to present principles behind them. Bayesian model averaging is suggested as a robust alternative for such methods.

Animals↗
PubMed2001

Analysis of complex survey data using SAS.

Commonly used statistical methods and software packages typically assume that observations are independent and identically distributed and fail to account for complex sampling designs when present. I suggest an approach to analyzing complex survey data in SAS, using weighted generalized estimating equations. Limited Monte Carlo simulations support the method. An example demonstrates application of the method and compares results to those from software commonly used in the analysis of complex survey data.

Aged↗
PubMed2001

Clinical trials for drug registrations in Asian-Pacific countries: proposal for a new paradigm from a statistical perspective.

The world has become more interdependent in the movement of free trade and global markets. The regulations for approval of new drugs in the Asian markets have always been an important issue in the free trade negotiation between the U.S.- and E.U.-based international manufacturers and the Asian-Pacific countries, since pharmaceuticals are of large trade value for them. In 1998 the University of Hong Kong and the Singapore National Medical Research Council jointly hosted the first Asian Clinical Trials Conference. The Society for Clinical Trials was invited as a collaborator for the event, which signified a milestone for interaction between the East and West in the discussion of clinical trials. Many have participated in the discussion of drug approval and registration issues for the Asian region based on the drug development experience in the United States. However, there are many interesting differences between the two regions, which lead to different approval processes for new drugs developed by the U.S.- and E.U.-based international manufacturers. This article highlights some regulatory dilemmas and some key statistical concepts pertinent to these differences. The purpose of this paper is to resolve the regional regulatory and scientific dilemma. A new paradigm of sample size design and data analysis for drug approval for countries in the Asian-Pacific region is proposed. The central premise is that substantial information from multicenter studies has already shown efficacy in the United States or the European Union when a drug manufacturer seeks marketing approval in an Asian country. This leads to the idea of a "consistency trial" using the method of Bayesian most plausible prediction. The method is illustrated with an example.

Asia↗
PubMed1997

Cultural orientation and use of cannabis and inhalants among secondary school children in Zimbabwe.

A survey among 3061 secondary school children in four provinces in Zimbabwe was conducted in 1994. In the present paper, the relationships between cultural and social factors and use of inhalants and cannabis are explored. Respondents were selected by means of a two-stage sample design, first based on a complete list of schools in the four provinces and subsequently on lists of students at the randomly selected schools. Stratification was based on the identification of four different sociocultural groups. Data collection followed standardised procedures and was conducted by a research team from University of Zimbabwe. Cultural orientation was operationalised by means of a Likert-type 14-item scale on choice of media, language and music. Exploratory principal component analysis revealed a two-factor solution, representing a global or Western cultural orientation and a local or Zimbabwean cultural orientation. Drug use by older siblings and best friends represented social factors. A combined model of cultural and social variables was subject to a multiple logistic regression analysis. Results revealed that the social variables and global cultural orientation were significantly associated with increased use of both drugs, whereas a local cultural orientation was found not to be associated with use of these substances. Findings are discussed in the light of historical and cultural factors.

Administration, Inhalation↗
PubMed1999

Geographies of health perception in Québec: a multilevel perspective.

Self perceived health is a widely used measure and, in Quebec, it has been shown to vary significantly between geographical areas. In the present study, these geographical variations are examined in a multilevel analysis in order to disentangle compositional (individual characteristics) and contextual (place) effects. The analysis recognizes four levels of variation: individual, household, local and regional. Similar analyses carried out in Britain, have considered only two levels: individual and local. Data come from the 1992-1993 Quebec Health and Social Survey, a general household survey using a stratified two-stage sampling design. Health perception (the response variable) is considered with a set of individual predictor characteristics reflecting gender, lifestyle, socio-economic conditions, marital status and social support. Results show the existence of significant local area variations in health perception after having allowed for individual characteristics and variations at the household level. At the regional level, however, no systematic and significant variations remain although some individual regions are found to have a significant impact on health perception.

Adult↗
PubMed2001

Ammonia concentration in human preovulatory ovarian follicles.

OBJECTIVES: To determine ammonia concentrations in both the direct environment of the oocyte, ovarian follicular fluid, and peripheral blood. STUDY DESIGN: Samples of preovulatory follicular fluid and antecubital venous blood were obtained from 23 randomly selected women attending an in vitro fertilization program in an academic department. Ammonia concentrations were measured using the indophenol method. RESULTS: In every patient examined, the ratio of ammonia concentration in follicular fluid to that in blood exceeded 1.0. Mean ammonia concentration in follicular fluid (38.01+/-2.61 microM) was significantly higher than that in blood (22.70+/-1.35 microM; P<0.001 paired Student's t test). CONCLUSIONS: There is an ammonia gradient from follicular fluid to blood. The human preovulatory oocyte grows in an environment of a moderately increased ammonia concentration. This study suggests that the preovulatory follicle is a source of ammonia production.

Adult↗
PubMed2003

Amniotic fluid and maternal serum leptin levels in pregnant women who subsequently develop preeclampsia.

OBJECTIVES: To study the correlation between amniotic fluid leptin levels and maternal serum leptin levels during the early second trimester, and to determine whether the ratios of amniotic fluid leptin levels to maternal serum leptin levels are elevated in pregnant women who subsequently develop preeclampsia. STUDY DESIGN: Samples from 120 pregnant women were included in this prospective study, of which 20 were from pregnant women who subsequently developed preeclampsia and 100 were from normal pregnant women. Both the amniotic fluid and the maternal serum leptin levels were ascertained by radioimmunoassay (RIA). RESULTS: A strong correlation between amniotic fluid leptin levels and maternal serum leptin levels was observed in both preeclamptic and normal pregnant women. In addition, the ratios of amniotic fluid leptin levels to maternal serum leptin levels were positively correlated to amniotic fluid leptin levels, but negatively correlated to maternal serum leptin levels. Furthermore, the ratios of amniotic fluid leptin levels to maternal serum leptin levels in preeclamptic women were significantly higher than those in normal pregnant women. CONCLUSIONS: Amniotic fluid leptin levels correlated with maternal serum leptin levels during the early second trimester. The ratios of amniotic fluid leptin levels to maternal serum leptin levels were elevated in preeclamptic women. However, the maternal serum leptin levels themselves showed no such elevation. Therefore, this elevated ratio may be a marker at the early stage of pregnancy in preeclamptic women.

Adult↗
PubMed1997

Current status of the multicenter randomized clinical trial on fetal oxygen saturation monitoring in the United States.

Current clinical methods of intrapartum fetal assessment are sensitive but poorly specific in detecting fetal compromise during labor. These limitations have substantially contributed to the escalating cesarean section rate which occurred in the US during the last several decades. Experimental and clinical research efforts directed towards application of the oxygen saturation monitor (pulse oximeter) to intrapartum fetal assessment have produced encouraging results. If this new method of fetal assessment is to enter the clinical arena, safety and efficacy issues must first be properly evaluated via randomized clinical trials. The purpose of this report is to describe the design of a multicenter randomized clinical trial of intrapartum fetal oxygen saturation monitoring recently begun in the US. Specific aspects of the trial, including purpose, study design, sample size estimates, control and test groups, inclusion and exclusion criteria, fetal heart rate classification, definition of normal fetal arterial oxygen saturation (SpO2), clinical management protocol, and assessment of maternal-fetal outcomes will be addressed.

Female↗
PubMed2001

Chronic pain in Australia: a prevalence study.

This study reports chronic pain prevalence in a randomly selected sample of the adult Australian population. Data were collected by Computer-Assisted Telephone Interview (CATI) using randomly generated telephone numbers and a two-stage stratified sample design. Chronic pain was defined as pain experienced every day for three months in the six months prior to interview. There were 17,543 completed interviews (response rate=70.8%). Chronic pain was reported by 17.1% of males and 20.0% of females. For males, prevalence peaked at 27.0% in the 65--69 year age group and for females, prevalence peaked at 31.0% in the oldest age group (80--84 years). Having chronic pain was significantly associated with older age, female gender, lower levels of completed education, and not having private health insurance; it was also strongly associated with receiving a disability benefit (adjusted OR=3.89, P<0.001) or unemployment benefit (adjusted OR=1.99, P<0.001); being unemployed for health reasons (adjusted OR=6.41, P<0.001); having poor self-rated health (adjusted OR=7.24, P<0.001); and high levels of psychological distress (adjusted OR=3.16, P<0.001). Eleven per cent of males and 13.5% of females in the survey reported some degree of interference with daily activities caused by their pain. Prevalence of interference was highest in the 55--59 year age group in both males (17.2%) and females (19.7%). Younger respondents with chronic pain were proportionately most likely to report interference due to pain, affecting 84.3% of females and 75.9% of males aged 20--24 years with chronic pain. Within the subgroup of respondents reporting chronic pain, the presence of interference with daily activities caused by pain was significantly associated with younger age; female gender; and not having private health insurance. There were strong associations between having interfering chronic pain and receiving disability benefits (adjusted OR=3.31, P<0.001) or being unemployed due to health reasons (adjusted OR=7.94, P<0.001, respectively). The results show that chronic pain impacts upon a large proportion of the adult Australian population, including the working age population, and is strongly associated with markers of social disadvantage.

Activities of Daily Living↗
PubMed2000

Sociodemographic correlates of tooth pain among adults: United states, 1989.

This study presents the sociodemographic distribution of tooth pain and the dental care utilization of affected individuals. Data for adults 20 years of age and over were derived from the 1989 National Health Interview Survey's supplements on dental health, orofacial pain, and health insurance (n=33073). Prevalence of tooth pain by socioeconomic status (SES) and adjusted odds ratios of reporting tooth pain in the past 6 months and of having no dental visits in the past year among persons reporting pain in the previous 6 months were computed taking into account the survey's complex sample design. Tooth pain in the past 6 months was reported by 14.5% (95% CI 14.0, 15.0) of adults aged 20-64 years and by 7.0% (95% CI 6.1, 7.9) of those 65 years and over. In the younger age group, tooth pain was more likely to be reported by those with low SES than it was by those with high SES; in the older age group, tooth pain was more likely reported by non-Hispanic blacks than it was by non-Hispanic whites or Hispanics. Of those reporting pain, younger and older non-Hispanic blacks and persons with lower educational attainment were more likely not to have a dental visit in the previous 12 months. Persons with low SES characteristics were more likely to report tooth pain and to endure their pain without the benefit of dental care while the pain was present.

Adult↗