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PubMedDate not supplied

[Results of a survey on periodontal prevention carried out in a test population in Bern].

In 1974 the authors carried out an inquiry about knowledge and behavior concerning periodontal prevention. Two-hundred persons from Berne and surroundings sampled by a random procedure were interviewed. It appeared that knowledge about the causes, consequences, prevention and therapy of periodontal disease was fragmentary. Accordingly prophylactic efforts of the interviewed persons were not very systematic. Often people believed in the effect of special remedies such as mouth-wash and special tooth-paste. They did not know that a perfect technique of oral hygiene is the basic requirement for periodontal prevention. It appeared that the advising function of the dentists was partially insufficient. Patients suffering from bleeding gums had not received adequate information regarding the seriousness of their situation, or they were referred to the special remedies mentioned in figure 3. Instruction of a perfect oral hygiene technique was therefore neglected.

Adult↗
PubMed1997

A conceptual model for establishing tolerance limits for analytic bias and imprecision based on variations in population test distributions.

A conceptual model is proposed for defining analytic bias limits utilizing the variations found in cumulative test value distributions. The model is based on the propositions that changes in analytic bias are more important than analytic imprecision in medical diagnoses and that analytic bias alters clinical specificity more than clinical sensitivity. The rationale for these propositions are presented along with a step-by-step procedure for estimating bias tolerance limits. These concepts are illustrated with an example using prostate-specific antigen. A second protocol is provided to define analytic imprecision tolerance limits, based on the quality control performance characteristics required to maintain the bias tolerance limits. This model can be applied to most chemistry, immunoassay, and hematologic quantitative assays. The relationship of this procedure to the published procedures using biologic variation for defining analytic tolerance limits is discussed.

Bias↗
PubMed1992

A randomized trial of a self-help smoking cessation intervention in a nonvolunteer female population: testing the limits of the public health model.

Reaching nonvolunteer female smokers with effective smoking cessation programs is a critical public health challenge. Smokers (N = 2,786) among 15,004 female members of a health maintenance organization who completed a routine needs assessment were invited into the "UCLA Preventive Health Behavior Study," consisting of five telephone interviews over 2 years assessing health practices. Participants (N = 1,396) were randomized into experimental or control conditions of an unsolicited, mailed, self-help smoking cessation program. Subjects were not alerted to the link between the program and the health study. Smoking status was assessed at 1, 6, 12, and 18 months. Across all subjects, point prevalence at 18 months was 18.62, and continuous abstinence was 2.71%. No difference was found between treatment and control groups regarding smoking status or readiness to stop smoking--raising questions about the value of mailing cessation materials to nonvolunteers. Quit rates increased over the 18-month follow-up; those still smoking at 18 months reported increased readiness to quit. Predictors at each follow-up point were examined multivariately.

Adolescent↗
PubMed2000

Testing Population Synthesis Models with Globular Cluster Colors.

We have measured an extensive set of UBVRIJHK colors for M31 globular clusters. We compare the predicted simple stellar population colors of three population synthesis models to the intrinsic colors of Galactic and M31 globular clusters. The best-fitting models fit the cluster colors very well: the weighted mean color offsets are all smaller than 0.05 mag. The most significant offsets between model and data are in the U and B passbands; these are not unexpected and are likely caused by problems with the spectral libraries used by the models. The metal-rich clusters (&sqbl0;Fe&solm0;H&sqbr0; greater, similar-0.8) are best fit by young (8 Gyr) models, while the metal-poor clusters are best fit by older (12-16 Gyr) models. If this range of globular cluster ages is correct, it implies that conditions for cluster formation must have existed for a substantial fraction of the galaxies' lifetimes.

Journal Article↗
PubMed1992

Genetic variation at five trimeric and tetrameric tandem repeat loci in four human population groups.

Trimeric and tetrameric short tandem repeats (STRs) represent a rich source of highly polymorphic markers in the human genome that may be studied with the polymerase chain reaction (PCR). We report the analysis of a multilocus genotype survey of 97-380 chromosomes in U.S. Black, White, Mexican-American, and Asian populations at five STR loci located on chromosomes 1, 4, 11, and X. The heterozygote frequencies of the loci ranged from 0.36 to 0.91 and the number of alleles from 6 to 20 for the 20 population and locus combinations. Relative allele frequencies exhibited differences between populations and unimodal, bimodal, and complex distributions. Although deviations were noted at some locus-population test combinations, genotype data from the loci were consistent overall with Hardy-Weinberg equilibrium by three tests. Population subheterogeneity within each ethnic group was not detected by two additional tests. No mutations were detected in a total of 860 meioses for two loci studied in the CEPH kindreds and five loci studied in other families. An indirect estimate of the mutation rates gave values from 2.3 x 10(-5) to 15.9 x 10(-5) for the five loci. Higher mutation rates appear to be associated with greater numbers of tandem repeats in the core motif. The most frequent genotype for all five loci combined appears to have a frequency of 7.59 x 10(-4). Together, these results suggest that trimeric and tetrameric STR loci are useful markers for the study of new mutations and genetic linkage analysis and for application to personal identification in the medical and forensic sciences.

Alleles↗
PubMed1978

Thyroid and obesity: survey of some function tests in a large obese population.

Tests of thyroid function in 493 obese patients were compared with thyroid function in 3076 non-obese patients. No differences in 131I uptake by the thyroid were observed at 6 h or 24 h; the frequency distribution was gaussian or normal in both populations; the frequencies of normal, high or low T3 and T4 values in the two populations were likewise comparable. Further, no correlation was found in the obese subjects between 131I uptake (6 h and 24 h), T3, T4 and overweight; on the other hand, there was a significant negative correlation between 131I uptake (6 h and 24 h) and age. It would appear that thyroid function is normal in obesity.

Adolescent↗
PubMed1992

Sonographic estimation of fetal weight in diabetic pregnancy.

OBJECTIVE: To investigate whether fetal weight estimation by ultrasound in diabetic pregnancy might be based upon fetal abdominal circumference (AC) alone. DESIGN: A retrospective study. SETTING: Diabetes Center, Rigshospitalet and Ultrasound Laboratory, Glostrup Hospital, Copenhagen. SUBJECTS: Eighty-six diabetic pregnant women who had an ultrasound study within 2 days before delivery. RESULTS: We assessed in 73 fetuses various formulas based upon biparietal diameter and AC against formulas based upon AC alone, and these were only marginally less effective than the more complex ones. In 86 fetuses an AC was available. These fetuses were divided into a study population and a test population. The linear model was customized for the study population. Evaluation on the test population showed that the relative error (error as a percentage of birthweight) in predicting birthweight had a standard deviation of 7.8%. The efficacy of AC in detecting fetuses greater than 4000 g was examined in the test population: If AC greater than 36.0 cm was chosen as criterion for macrosomia the positive and negative predictive values were 80% (8/10) and 91% (30/33), respectively. CONCLUSION: Formulas for estimating fetal weight in diabetic pregnancy based on AC alone are almost as effective as more complex ones. We recommend a simple linear formula of fetal weight as a function of AC.

Body Weight↗
PubMed1999

Dynamical role of predators in population cycles of a forest insect: An experimental test

Population cycles occur frequently in forest insects. Time-series analysis of fluctuations in one such insect, the southern pine beetle (Dendroctonus frontalis), suggests that beetle dynamics are dominated by an ecological process acting in a delayed density-dependent manner. The hypothesis that delayed density dependence in this insect results from its interaction with predators was tested with a long-term predator-exclusion experiment. Predator-imposed mortality was negligible during the increase phase, grew during the year of peak population, and reached a maximum during the period of population decline. The delayed nature of the impact of predation suggests that predation is an important process that contributes significantly to southern pine beetle oscillations.

Journal Article↗
PubMedDate not supplied

Estimated analytic validity of HFE C282Y mutation testing in population screening: the potential value of confirmatory testing.

PURPOSE: The purpose of this study was to estimate analytic sensitivity and specificity of HFE testing for C282Y homozygosity in the hypothetical setting of population screening for hemochromatosis. METHODS: We analyzed published results of the Molecular Genetics Survey performed by the American College of Medical Genetics/College of American Pathologists between 1998 and 2002, taking into account its educational nature. RESULTS: Analytic sensitivity for C282Y homozygosity is 98.4% (95% CI 95.9%-99.5%). The analytic specificity is 99.8% (99.4%-99.9%). At a frequency of 40 per 10,000 for the homozygous genotype, the analytic positive predictive value is 66%. CONCLUSION: HFE testing for C282Y homozygosity is highly reliable. Homozygosity is uncommon in population screening, however, and confirmatory testing should be considered.

Genetic Testing↗
PubMed2002

Statistical properties of new neutrality tests against population growth.

A number of statistical tests for detecting population growth are described. We compared the statistical power of these tests with that of others available in the literature. The tests evaluated fall into three categories: those tests based on the distribution of the mutation frequencies, on the haplotype distribution, and on the mismatch distribution. We found that, for an extensive variety of cases, the most powerful tests for detecting population growth are Fu's F(S) test and the newly developed R(2) test. The behavior of the R(2) test is superior for small sample sizes, whereas F(S) is better for large sample sizes. We also show that some popular statistics based on the mismatch distribution are very conservative.

Computer Simulation↗
PubMed2004

Population and individual minimal modeling of the frequently sampled insulin-modified intravenous glucose tolerance test.

Population approaches are more robust estimators of insulin sensitivity (SI) and glucose effectiveness (SG) with the minimal model of glucose kinetics during an intravenous glucose tolerance test (IVGTT). We assessed the performance of 3 population methods, iterative two-stage (ITS), Bayesian hierarchical Markov chain Monte Carlo (MCMC), and NONMEM first-order conditional estimation (FOCE) with interaction (NM), and made a comparison with the standard two-stage method (STS) employing the weighted nonlinear regression analysis. To evaluate accuracy of individual and population estimates, 40 simulated insulin-modified frequently sampled IVGTTs (IM-FSIVGTT) were derived from real IM-FSIVGTTs (0.3 g glucose per kg body weight with 0.02 U/kg insulin at 20 minutes; 30 samples over 180 minutes) performed in 40 healthy Caucasian subjects (male/female, 22/18; age, 46 +/- 9 years; body mass index [BMI], 26.7 +/- 5.7 kg. m(-2); mean +/- SD). The population methods assumed a log-normal population distribution of parameters. All methods gave a similar but overestimated population SG by 9% to 13%. Population SI was underestimated to a different degree by the methods (STS 6%, ITS 10%, MCMC 13%, and NM 7%). The between-subject variability of SG was overestimated by STS and underestimated by the population methods (true 33%, STS 40%, ITS 19%, MCMC 24%, NM 24%; coefficient of variation). For SI, this quantity was well estimated by all methods (true 79%, STS 80%, ITS 82%, MCMC 83%, NM 82%). The results for individual estimates indicate that STS performs better than the population methods when estimating SI (STS 12%, ITS 16%, MCMC 16%, NM 16%; 1 outlying subject excluded; root mean squared error expressed as percent of mean) but worse for SG (STS 28%, ITS 21%, MCMC 20%, NM 19%). We conclude that the robust performance of population approaches, preventing parameter estimation failures associated with the nonlinear regression analysis, is not required with IM-FSIVGTT in subjects with normal glucose tolerance. The standard two-stage technique is the preferred method under such circumstances.

Adult↗
PubMed1997

Smoking during pregnancy measured by population cotinine testing.

AIM: To establish a baseline cross-sectional prevalence of maternal smoking, measured by antenatal serum cotinine testing, in a population of pregnant women. METHODS: Residual sera from first and second routine antenatal blood samples were collected anonymously over a six-month period for pregnancies within the Canterbury region. Cotinine levels were measured by an ELISA test with a result of > 14 ng/mL indicative of active smoking. Only pregnancies ending in a confirmed live birth were considered in smoking prevalence calculations. There was a total of 1948 eligible residual blood samples. RESULTS: Of the 414 residual blood samples available for the first two months of pregnancy, 146 (35.3%) were found to be positive for cotinine. Smoking prevalence decreased over pregnancy so that by the third trimester 225 (26.8%) of 838 samples were cotinine positive. Infants born from smoking mothers had significantly lower birth weights. CONCLUSIONS: In 1994, a third of women tested in early pregnancy and a quarter of women tested in late pregnancy were identified as being smokers. Repeated objective cross-sectional surveys will allow accurate assessment of the efficacy of smokefree interventions both before and during pregnancy.

Birth Weight↗
PubMed2007

A multivariate test for population bioequivalence.

In this article, we propose a multivariate generalization of the criteria for testing univariate population bioequivalence. Recently, a number of approaches for testing multivariate equivalence have appeared in the literature. Most of them consider a multivariate equivalence region, which implies simultaneous comparison of means in each dimension. In contrast, our proposal combines a comparison of means and a comparison of variances into a single aggregate criterion, using the trace of the covariance matrix as a scalar measure of the total variability. We use a confidence interval approach to multivariate population bioequivalence testing, similar to the univariate case. Two versions of the modified large-sample confidence interval for the linearized multivariate criterion are constructed. In a simulation study, we evaluate the empirical coverage of these confidence intervals and rejection rates of the corresponding tests in finite samples. The proposed methodology is illustrated with an example of testing equivalence of the spray pattern of nasal sprays.

Bayes Theorem↗