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PubMed2001

Tay-Sachs screening in the Jewish Ashkenazi population: DNA testing is the preferred procedure.

A unique screening program for the identification of Tay-Sachs Disease (TSD) heterozygotes has been performed in the tradi- tional Orthodox Ashkenazi Jewish (AJ) community since 1983. In recent years the program has utilized the biochemical assay for the determination of hexosaminidase A levels by the heat inactivation technique as well as by direct DNA analysis. The three mutations which were analyzed were those that have been shown to be prevalent among AJ TSD patients and carriers, namely the four nucleotide insertion mutation in exon 11 (1278+TATC), the splice mutation at the 5' end of intron 12 (1421+1g-->c), and the adult mutation, a Gly(269)-->Ser substitution in exon 5 (G269S). A total of 103,133 individuals were tested by biochemical analysis, and 38,197 of them were also assayed by DNA testing. Furthermore, 151 chromosomes from TSD patients or obligate heterozygotes were subjected to DNA analysis for one of the three mutations. DNA testing of the latter identified one of the three AJ mutations in every case, predicting a very high detection rate of heterozygotes in this community by this method. By contrast, the sensitivity of the enzyme assay ranged from 93.1% to 99.1% depending on the exclusion (inclusion) of inconclusive results as positive, while the specificity ranged from 88.1% to 98.8% depending on the inclusion (exclusion) of inconclusive results as positive. Our results strongly support the use of DNA testing alone as the most cost-effective and efficient approach to carrier screening for TSD in individuals of confirmed Ashkenazi Jewish ancestry.

DNA↗
PubMed2006

Personality traits in Sardinia: testing founder population effects on trait means and variances.

Potential founder population effects on personality trait means and variances were examined in a large, genetically homogeneous sample (N=5,669) from the Ogliastra, an isolated region within Sardinia, Italy. The Italian version of the Revised NEO Personality Inventory showed good psychometric properties: Internal consistency reliabilities ranged from 0.80 to 0.87; the factor structure replicated the American normative structure; and associations with education and gender replicated cross-cultural patterns. The hypothesis that mean trait levels in the Sardinian founder population would differ from mainland Italian values was not supported. Phenotypic variation in this founder population was within the range found in other cultures. However, the hypothesis of restricted phenotypic variation was supported for all five factors and 28 of the 30 facets when a Sardinian subsample matched on age, sex, and education was compared to a mainland Italian sample. The genetic homogeneity effect on the phenotypic expression of complex traits merits further exploration.

Analysis of Variance↗
PubMed1993

Assessment of the knowledge of graduating American dental students about the panoramic image.

The objective of this study was to assess the capability of graduating dental students to identify the causes of undiagnostic panoramic images and to interpret anatomic landmarks on panoramic films. Seventeen dental schools were represented by 311 students. A radiology faculty member at each institution completed a questionnaire that addressed lecture time and experience provided to students in panoramic radiography. The faculty member administered a test instrument comprised of several panoramic radiographs that demonstrated one or more labeled anatomic structures, technical errors, or projection artifacts and multiple choice questions that addressed each entity. The mean percentage correct for the tested population on the entire test instrument was 72.9%. The mean percentage correct for questions addressing anatomy, error and artifact recognition, and error correction was 84.0%, 61.4% and 45.2%, respectively. Factors that significantly (p < 0.05) affected student performance were the number of lecture hours provided, whether or not students took panoramic radiographs of patients, and the method of student selection as participants. Laboratory or self-study projects and the number of panoramic radiographs (> or = 1) taken of patients did not significantly affect student performance on the test instrument.

Analysis of Variance↗
PubMed1996

Black/white differences in the relationship of maternal age to birthweight: a population-based test of the weathering hypothesis.

This study seeks to explore if early health deterioration ('weathering') among young adult African American women contributes to observed increases with maternal age in the black/white disparity in birth outcome. Theoretically, 'weathering' is constructed as being a physical consequence of social inequality. Thus, we also examine whether African American mothers vary in their age trajectories of poor birth outcome with respect to social class. Black or white singleton first births to Michigan residents aged 15-34 in 1989 (N = 54,888 births) are analyzed, using data drawn from linked birth and infant death certificates augmented with census-based economic information. We find among blacks, but not whites, advancing maternal age above 15 years is associated with increased odds of LBW and VLBW. Among blacks in low-income areas, the odds of LBW increase 3-fold, and of VLBW 4-fold, between maternal ages 15 and 34. The findings suggest that African American women, on average, and those residing in low-income areas, in particular, experience worsening health profiles between their teens and young adulthood, contributing to their increasing risk of LBW or VLBW with advancing maternal age and to the black-white gap in this risk. The findings suggest the importance of comprehensive prevention strategies to improve the health of socioeconomically disadvantaged African American women prior to pregnancy and the reduction of social inequalities that impact health.

Adolescent↗
PubMed2004

A comparison of autogenous/reactive obsessions and worry in a nonclinical population: a test of the continuum hypothesis.

Employing the autogenous-reactive model of obsessions (Behaviour Research and Therapy 41 (2003) 11-29), this study sought to test a hypothesized continuum where reactive obsessions fall in between autogenous obsessions and worry with respect to several thought characteristics concerning content appraisal, perceived form, and thought triggers. Nonclinical undergraduate students (n=435) were administered an online packet of questionnaires designed to examine the three different types of thoughts. Main data analyses included only those displaying moderate levels of obsessions or worries (n=252). According to the most distressing thought, three different groups were formed and compared: autogenous obsession (n=34), reactive obsession (n=76), and worry (n=142). Results revealed that (a) relative to worry, autogenous obsessions were perceived as more bizarre, more unacceptable, more unrealistic, and less likely to occur; (b) autogenous obsessions were more likely to take the form of impulses, urges, or images, whereas worry was more likely to take the form of doubts, apprehensions, or thoughts; and (c) worry was more characterized by awareness and identifiability of thought triggers, with reactive obsessions through these comparisons falling in between. Moreover, reactive obsessions, relative to autogenous obsessions, were more strongly associated with both severity of worry and use of worrying as a thought control strategy. Our data suggest that the reactive subtype represents more worry-like obsessions compared to the autogenous subtype.

Adolescent↗
PubMed1998

Assumption testing in population pharmacokinetic models: illustrated with an analysis of moxonidine data from congestive heart failure patients.

Deriving a population pharmacokinetic model from real data is always associated with numerous assumptions. Violations of these assumptions, especially if undetected, may lead to inappropriate conclusions being made from the analysis. Routinely, only a few of the assumptions are explicitly stated and justified in the reporting of a population model. Here, we attempt to be exhaustive in the presentation of the assumptions made in the course of an analysis of moxonidine pharmacokinetics. The different ways that assumptions were justified, through experience, graphical examination, or additional modeling, are outlined. Models for relaxing assumptions regarding the covariate and statistical submodels, not previously reported in the area of population pharmacokinetic modeling, are also described.

Adult↗
PubMed1979

Statistical design of toxicity assays: role of genetic structure of test animal population.

This paper concerns certain statistical aspects of the problem of among-strain differences in cancer susceptibility and how these differences may affect the design of toxicity assays. First, the data of Innes et al. (1969) were examined to investigate the magnitude of within-study, between-strain differences in tumor induction. Although there was a very high overall association between mouse strains with respect to the induction of hepatomas, evidence of strain-to-strain variability was found for several compounds. Next, a number of long-term carcinogenicity studies with DDT were considered, and among-strain differences in cancer susceptibility for this compound were noted. Finally, it was shown that if susceptible subgroups do exist, and certain simplifying assumptions are made, then in many cases tumor increases can be detected more readily by studying several inbred mouse strains rather than a single outbred stock.

Animals↗
PubMed2006

Do self-report instruments allow meaningful comparisons across diverse population groups? Testing measurement invariance using the confirmatory factor analysis framework.

Comparative public health research makes wide use of self-report instruments. For example, research identifying and explaining health disparities across demographic strata may seek to understand the health effects of patient attitudes or private behaviors. Such personal attributes are difficult or impossible to observe directly and are often best measured by self-reports. Defensible use of self-reports in quantitative comparative research requires not only that the measured constructs have the same meaning across groups, but also that group comparisons of sample estimates (eg, means and variances) reflect true group differences and are not contaminated by group-specific attributes that are unrelated to the construct of interest. Evidence for these desirable properties of measurement instruments can be established within the confirmatory factor analysis (CFA) framework; a nested hierarchy of hypotheses is tested that addresses the cross-group invariance of the instrument's psychometric properties. By name, these hypotheses include configural, metric (or pattern), strong (or scalar), and strict factorial invariance. The CFA model and each of these hypotheses are described in nontechnical language. A worked example and technical appendices are included.

Bias↗
PubMed2005

Iron loading and morbidity among relatives of HFE C282Y homozygotes identified either by population genetic testing or presenting as patients.

BACKGROUND AND AIMS: Although most cases of hereditary haemochromatosis are associated with homozygosity for the C282Y mutation of the HFE gene, clinical penetrance varies and other genes may modify disease expression. If so, relatives from clinically affected families, by inheriting such genes, may accumulate more iron. To seek evidence for this, we compared iron status and morbidity in unselected first degree relatives of two groups of index cases from South Wales, namely asymptomatic C282Y homozygotes identified by genetic screening of blood donors (n = 56) and C282Y homozygous haemochromatosis patients presenting clinically (n = 60). METHODS: All participating relatives had a structured interview, clinical assessment, and laboratory investigations. Health related quality of life was measured (SF-36 version 2). RESULTS: In total, 92% of 180 eligible first degree relatives were interviewed in the "screened" family group and 85% of 143 eligible relatives in the "patient" group. Of 59 relatives homozygous for C282Y, 76% of men and 32% of women had the "iron phenotype" (raised transferrin saturation and serum ferritin). Logistic regression modelling of the iron phenotype risk showed that 42% of the initial model deviance could be explained by homozygosity for C282Y, another 6% by lifestyle factors, and 6% by being male. Family group membership was not a significant risk factor. Morbidity and SF-36 scores did not differ significantly either between C282Y homozygotes and relatives lacking C282Y, or between C282Y homozygotes from the "screened" and "patient" groups. Serious morbidity (including cirrhosis) was low in both groups of relatives. CONCLUSIONS: HFE C282Y homozygosity has a high penetrance for iron accumulation but a low clinical penetrance. Lack of excess morbidity among C282Y homozygous relatives of index cases who presented clinically suggests that residual unknown genetic or environmental factors do not greatly influence clinical outcome among C282Y homozygotes.

Adolescent↗
PubMed2005

Activation of the RAS pathway is predictive for a chemosensitive phenotype of acute myelogenous leukemia blasts.

PURPOSE: Activation of the RAS pathway plays a major role in cancer cells. In acute myeloid leukemia (AML), mutations of the RAS genes cause an intrinsic activation of this pathway. Until now, clinical studies could not find clear association of RAS mutations with the clinical outcome after AML therapy. This could be due to alternative initiating events for activation of the RAS pathway like constitutive tyrosine kinase activation or mutations in Ras-regulating genes. EXPERIMENTAL DESIGN: In total, 191 AML patients (126 as training population and 65 as test population) were studied for Ras activity with a glutathione S-transferase pull-down assay using Raf binding of activated Ras. RESULTS: AML samples showed a wide range of Ras activity values, which was in contrast to normal bone marrow donors who showed no or very limited Ras activity. Using a Ras binding score based on semiquantitative Western blotting, we defined patients with strong Ras activity and compared Ras activity with RAS mutation. Surprisingly, only a minority of RAS mutated AML samples (22.2%) showed strong Ras activity, whereas 25 patients presented strong Ras activity in the absence of RAS mutations. Clinical outcome did not show differences according to RAS mutations. In contrast, Ras activity predicted for a high response rate (P <0.05) and proved to be an independent factor for overall survival rate (P <0.05) in younger AML patients receiving high-dose 1-beta-D-arabinofuranosylcytosine as induction therapy. CONCLUSION: The data highlight the role for alternative pathways of Ras activation without RAS mutations. Intrinsically activated Ras seems to increase sensitivity of the AML blast to high-dose 1-beta-D-arabinofuranosylcytosine therapy.

Antimetabolites, Antineoplastic↗
PubMed1999

Diagnosis of urogenital Chlamydia trachomatis infection by use of DNA amplification.

Numerous studies on DNA amplification and diagnosis of C. trachomatis infections have been performed since the first PCR for detection of C. trachomatis in clinical samples was described in 1990, but optimal sample preparation procedures are still lacking. The major problem in evaluating the diagnostic performance of the DNA amplification methods is that there is no clinical or microbiological reference standard for C. trachomatis infection. The evaluated diagnostic performance will therefore always be a reflection of of the chosen comparator(s). Despite this, it seems that the DNA amplification methods are more sensitive than the cell culture techniques and the techniques based on immunology. Compared with the tests based on immunology the specificity is also improved, which makes the DNA amplification methods useful for sample types contaminated with organisms cross-reacting in the immunologically based methods, i.e. pharyngeal and rectal swab samples. However, the specificity and thereby the predictive value of a positive test is not optimal. Since the predictive value of a positive test is highly influenced by the prevalence in the tested population, evaluation of applied tests is constantly needed, especially since the prevalence may be expected to decrease with intensified test activity and due to changes in safe sex practices after the advent of AIDS. The improved sensitivity of the DNA amplification methods allows the use of sample material in which the content of Chlamydia organisms is lower than in conventional swab samples, i.e. urine, semen, and vaginal secretions can be used as sample material. these samples can be obtained by the individuals themselves, and since transport conditions seem less critical for the test performance, samples can also be taken in the privacy of the home and subsequently mailed by the individual directly to the diagnostic laboratory. Such strategy for testing has led to improved partner tracing and universal screening, compared with traditional swab examinations at physicians' offices. Tests with an optimal diagnostic performance have not yet been reached, and several sample categories have not been studied sufficiently. The societal implications of the use of self-collected samples and universal screening have not been studied in full, but a milestone for new strategies in detection and preventing urogenital C. trachomatis epidemics has been reached with the availability of DNA amplification techniques.

Chlamydia Infections↗