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Results for “multiple tests”

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At least 973 records · Page 54Linked to original sources

PubMed1995

The influence of maternal weight on human chorionic gonadotropin in the multiple-marker screening test for fetal Down syndrome.

OBJECTIVE: Our purpose was to determine the effect of maternal weight on human chorionic gonadotropin concentration in the multiple-marker screening test for fetal Down syndrome. STUDY DESIGN: Two genetics databases were used: database I contained the results of 8297 multiple-marker screening tests and database II contained the results of 1936 multiple-marker screening tests and fetal karyotypes. RESULTS: The overall screen-positive rate in database I was 7.1%; it was 7.5% in patients weighing < 180 pounds and 5.1% in patients weighing > or = 180 pounds (p = 0.001). Weight significantly affected the screen-positive rate only in women > or = 30 years old (p = 0.003 for 30 to 34 years, p = 0.00004 for > or = 35 years). A weight correction formula was derived; when applied to database II it eliminated individual weight-related differences but had no effect on the overall screen-positive rate or Down syndrome detection rate. CONCLUSIONS: Human chorionic gonadotropin concentration is affected by maternal weight. A weight correction formula eliminates individual weight-related differences in the screen-positive rate but has no discernible effect on the overall screen-positive or Down syndrome detection rates.

Adult↗

PubMed2000

Effectiveness of antenatal corticosteroid administration after preterm premature rupture of the membranes.

OBJECTIVE: This study was undertaken to determine the effect of antenatal betamethasone administration on the incidences of respiratory distress syndrome, intraventricular hemorrhage, and perinatal infectious morbidity in the setting of preterm premature rupture of membranes. STUDY DESIGN: We performed a nonconcurrent prospective analysis of women with singleton pregnancies who were delivered between 24 and 32 weeks' gestation after preterm premature rupture of membranes. Patients were subdivided into 2 groups according to betamethasone exposure: (1) none (control group) and (2) two 12-mg doses in a 24-hour interval on admission (single-course group). Patients who received >2 doses of betamethasone were excluded. All patients received broad-spectrum prophylactic antibiotics. Data were analyzed with the Student t test, the chi(2) test, and the Fisher exact test. Multiple logistic regression analyses incorporated multiple variables considered risk factors for respiratory distress syndrome and intraventricular hemorrhage. P <.05 for all 2-tailed tests was considered significant. RESULTS: A total of 362 patients were included, with 203 in the control group and 159 in the single-course group. Patients in these groups were delivered at 31.0 +/- 3.0 and 30.2 +/- 2.7 (mean +/- SD) weeks' gestation, respectively. The groups were similar with respect to selected demographic characteristics, latency until delivery, mode of delivery, birth weight, and maternal group B streptococcal colonization status. Univariate analysis demonstrated significant decreases in the frequencies of both respiratory distress syndrome (odds ratio, 0.31; 95% confidence interval, 0.2-0.5) and grade III/IV intraventricular hemorrhage (odds ratio, 0.14; 95% confidence interval, 0.1-0.6) in the single-course group. The frequencies of early neonatal sepsis, chorioamnionitis, endometritis, and neonatal death were similar between groups. Multiple logistic regression analyses determined that a single course of betamethasone was independently associated with reductions in the frequencies of both respiratory distress syndrome (odds ratio, 0.16; 95% confidence interval, 0.1-0.4) and grade III/IV intraventricular hemorrhage (odds ratio, 0.18; 95% confidence interval, 0.1-0.4). CONCLUSIONS: A single course of betamethasone administered antenatally to patients with preterm premature rupture of membranes was associated with decreases in the frequencies of both respiratory distress syndrome and advanced grades of intraventricular hemorrhage without any increase in perinatal infectious morbidity.

Adult↗

PubMed2005

The arthroscopic active compression test.

Pathology of the biceps tendon is often a factor in the pathogenesis of shoulder pain. However, diagnosis and management of such pathology remains controversial. Multiple tests have been described to identify pathology related to the biceps tendon and biceps anchor. The active compression test is one such test that has been used clinically to identify patients with superior labral/biceps anchor pathology. An arthroscopic version of this test is described to identify biceps pathology intraoperatively and to aid the surgeon in making diagnostic and treatment decisions.

Arthroscopy↗

PubMed2004

Preterm fetal hypoxia-ischemia causes hypertonia and motor deficits in the neonatal rabbit: a model for human cerebral palsy?

Prenatal hypoxia-ischemia to the developing brain has been strongly implicated in the subsequent development of the hypertonic motor deficits of cerebral palsy (CP) in premature and full-term infants who present with neonatal encephalopathy. Despite the enormous impact of CP, there is no animal model that reproduces the hypertonia and motor disturbances of this disorder. We report a rabbit model of in utero placental insufficiency, in which hypertonia is accompanied by marked abnormalities in motor control. Preterm fetuses (67-70% gestation) were subjected to sustained global hypoxia. The dams survived and gave spontaneous birth. At postnatal day 1, the pups that survived were subjected to a battery of neurobehavioral tests developed specifically for these animals, and the tests were videotaped and scored in a masked manner. Newborn pups of hypoxic groups displayed significant impairment in multiple tests of spontaneous locomotion, reflex motor activity, and the coordination of suck and swallow. Increased tone of the limbs at rest and with active flexion and extension were observed in the survivors of the preterm insult. Histopathological studies identified a distinct pattern of acute injury to subcortical motor pathways that involved the basal ganglia and thalamus. Persistent injury to the caudate putamen and thalamus at P1 was significantly correlated with hypertonic motor deficits in the hypoxic group. Antenatal hypoxia-ischemia at preterm gestation results in hypertonia and abnormalities in motor control. These findings provide a unique behavioral model to define mechanisms and sequelae of perinatal brain injury from antenatal hypoxia-ischemia.

Animals↗

PubMed2001

Correcting for multiple analyses in genomewide linkage studies.

The dissection of complex traits frequently calls for multiple analyses to be performed, including the use of both multiple phenotypes and genetic models. These multiple phenotypes and models are often not independent, and hence the necessary correction for the multiple testing is not straightforward. In this paper we offer a new approach to address the problem of how to correct for non-independent multiple analyses in genomewide linkage studies. We describe one method of how to determine the number of 'effectively independent' tests performed in a linkage study using simple linear regression techniques. Further we describe how to use such information to establish genomewide significance thresholds for infinitely dense genomewide maps.

Chromosome Mapping↗

PubMed1996

Effect of parity correction on Down syndrome detection by the multiple-marker screening test.

OBJECTIVE: Our purpose was to determine whether maternal parity affects analyte levels in the multiple-marker screening test for Down syndrome and to derive a correction factor and determine its effect on Down syndrome detection and screen-positive rates. STUDY DESIGN: Our database consisted of 3039 multiple-marker screening test results and corresponding fetal karyotypes (2983 euploid and 56 Down syndrome). Cases were grouped by maternal parity as follows: 0 (n = 848), 1 (n = 1140), or > or = 2 (n = 1051). The mean multiple of the median of maternal serum alpha-fetoprotein, estriol, and human chorionic gonadotropin was determined for each group. A correction factor was derived for each parity group and applied to the database. Parity-corrected Down syndrome detection rates and screen-positive rates were determined. RESULTS: Parity significantly affected the mean multiple of the median of human chorionic gonadotropin levels (p = 0.0001) but did not affect the values for estriol or maternal serum alpha-fetoprotein. Application of a parity correction factor for human chorionic gonadotropin increased the Down syndrome detection rate in women who had two or more pregnancies from 71% to 82% without increasing the overall screen-positive rate. CONCLUSION: Human chorionic gonadotropin levels are significantly lower in multiparous women. Correcting human chorionic gonadotropin for maternal parity increases Down syndrome detection for women who had two or more pregnancies without affecting the overall screen-positive rate.

Adult↗

PubMed2005

Variable selection pressures across lineages in Trichodesmium and related cyanobacteria based on the heterocyst differentiation protein gene hetR.

Due to the irreversible inhibition of nitrogenase by O2, N2 fixation is incompatible with the oxygenic photosynthesis of cyanobacteria. These organisms have therefore evolved various strategies for growing diazotrophically. One group of N2-fixing cyanobacteria has specialized cells, heterocysts, which contain the nitrogenase, lack the oxygenic photosystem II, and are virtually anoxic inside as the result of respiratory activity and a thick glycolipid cell wall. The hetR gene encodes a serine protease which is thought to be involved in the regulation of heterocyst development and in DNA binding. Although hetR is also present in many non-heterocystous N2-fixing cyanobacteria, its function in these organisms is unknown. In this study, hetR sequences of the N2-fixing, non-heterocystous cyanobacterium Trichodesmium spp. and related genera were examined for signatures of selection. In parsimony- or distance-based hetR phylogenies, the filamentous non-heterocystous cyanobacteria Symploca sp. and Leptolyngbya sp. were closest to Trichodesmium sp. However, accommodating molecular attributes of hetR such as nucleotide frequencies and rate heterogeneity in phylogenetic analyses suggested that many other genera could not be excluded as sister taxa of Trichodesmium. Maximum likelihood analysis of the dN/dS ratio (omega) showed that-irrespective of the use of Symploca, Leptolyngbya, or more distant taxa as an outgroup-the lineage between an outgroup and Trichodesmium (omega1=0.02-0.05) and a lineage leading to Trichodesmium erythraeum (omega1=0.02) were under much stronger purifying selection than the other lineages in Trichodesmium (omega0=0.13-0.32). Although the results from the maximum likelihood analyses are most trustworthy because of codon usage bias in Trichodesmium, the results from a simpler tree-based McDonald-Kreitman test were in general agreement. Due to their quite different assumptions, the combination of these two methods of analysis circumvents multiple testing which, in general, is problematic when using branch models. Although the causal selective forces underlying the substitution patterns in hetR have not yet been identified, these findings parallel the variety of physiological, molecular, and behavioral differences in cyanobacteria related to N2 fixation. The heterogeneity of selection pressures in Trichodesmium is more surprising, because multiple adaptation mechanisms have not been described in this genus.

Bacterial Proteins↗

PubMed1993

Diagnosis of primary tuberculosis in children by amplification and detection of mycobacterial DNA.

Standard microbiologic techniques were compared with a rapid diagnostic method based on the amplification by polymerase chain reaction (PCR) of a fragment of the IS6110 insertion element (present in multiple copies in the Mycobacterium tuberculosis genome) for the detection of M. tuberculosis in specimens obtained from children diagnosed as having primary tuberculosis on clinical grounds. Two (n = 7) or three (n = 15) gastric aspirates were obtained from the 22 children with primary tuberculosis. All specimens were negative for mycobacteria by acid-fast staining and culture. When DNA was purified from the clinical specimens and aliquots of each sample were amplified in duplicate, 15 of 59 (25%) specimens gave at least one positive result. Increasing beyond two the number of times that samples were tested did not appreciably improve sensitivity. Testing multiple samples from the same individual increased the diagnostic yield. Thus, when three different samples from the same subject were tested two times each, two or more positive results were obtained from 9 of 15 children with primary tuberculosis but 0 of 17 control subjects. Samples from children with symptoms, recent contact with patients with active tuberculosis, vesicular tuberculin responses, or abnormal chest radiographs were more frequently positive than those from patients whose only manifestation of tuberculosis was a positive (but not vesicular) tuberculin response. Thus, M. tuberculosis DNA can be detected by PCR in gastric aspirates of many children with primary tuberculosis, despite that specimens from these patients are negative by culture. Multiple samples must be tested to optimize the diagnostic yield.

Bacteriological Techniques↗

PubMed2006

High throughput SNP and expression analyses of candidate genes for non-syndromic oral clefts.

BACKGROUND: Recent work suggests that multiple genes and several environmental risk factors influence risk for non-syndromic oral clefts, one of the most common birth defects in humans. Advances in high-throughput genotyping technology now make it possible to test multiple markers in many candidate genes simultaneously. METHODS: We present findings from family based association tests of single nucleotide polymorphism (SNP) markers in 64 candidate genes genotyped using the BeadArray approach in 58 case-parent trios from Maryland (USA) to illustrate how multiple markers in multiple genes can be analysed. To assess whether these genes were expressed in human craniofacial structures relevant to palate and lip development, we also analysed data from the Craniofacial and Oral Gene Expression Network (COGENE) consortium, and searched public databases for expression profiles of these genes. RESULTS: Thirteen candidate genes showed significant evidence of linkage in the presence of disequilibrium, and ten of these were found to be expressed in relevant embryonic tissues: SP100, MLPH, HDAC4, LEF1, C6orf105, CD44, ALX4, ZNF202, CRHR1, and MAPT. Three other genes showing statistical evidence (ADH1C, SCN3B, and IMP5) were not expressed in the embryonic tissues examined here. CONCLUSIONS: This approach demonstrates how statistical evidence on large numbers of SNP markers typed in case-parent trios can be combined with expression data to identify candidate genes for complex disorders. Many of the genes reported here have not been previously studied as candidates for oral clefts and warrant further investigation.

Chromosome Mapping↗

PubMed2002

Development and validation of the neck dissection impairment index: a quality of life measure.

OBJECTIVES: To validate a health-related quality-of-life (QOL) instrument for patients following neck dissection and to identify the factors that affect QOL following neck dissection. DESIGN: Cross-sectional validation study. SETTING: The outpatient clinic of a tertiary care cancer center. PATIENTS: Convenience sample of 54 patients previously treated for head and neck cancer who underwent a selective neck dissection or modified radical neck dissection (64 total neck dissections). Patients had a minimum postoperative convalescence of 11 months. Thirty-two underwent accessory nerve-sparing modified radical neck dissection, and 32 underwent selective neck dissection. MAIN OUTCOME MEASURE: A 10-item, self-report instrument, the Neck Dissection Impairment Index (NDII), was developed and validated. Reliability was evaluated with test-retest correlation and internal consistency using the Cronbach alpha coefficient. Convergent validity was assessed using the 36-Item Short-Form Health Survey (SF-36) and the Constant Shoulder Scale, a shoulder function test. Multiple variable regression was used to determine variables that most affected QOL following neck dissection RESULTS: The 10-item NDII test-retest correlation was 0.91 (P<.001) with an internal consistency Cronbach alpha coefficient of.95. The NDII correlated with the Constant Shoulder Scale (r = 0.85, P<.001) and with the SF-36 physical functioning (r = 0.50, P<.001) and role-physical functioning (r = 0.60, P<.001) domains. Using multiple variable regression, the variables that contributed most to QOL score were patient's age and weight, radiation treatment, and neck dissection type. CONCLUSIONS: The NDII is a valid, reliable instrument for assessing neck dissection impairment. Patient's age, weight, radiation treatment, and neck dissection type were important factors that affect QOL following neck dissection.

Aged↗

PubMed2002

Score tests for detecting excess risks around putative sources.

Focused clustering studies examine raised disease risk around prespecified point sources. As statistical methods to detect such clusters, Stone's maximum likelihood ratio test is popular, against the general ordered alternatives and score tests which score each case the reciprocal of the distance from a point source as a surrogate exposure. This paper considers extensions of score tests in that (i) they can allow us to select the best among prespecified parametric exposure functions to avoid multiple testing problems and (ii) they can be applied to a possible situation where the hazardous substance levels have a peak at some distance from a point source. Simulation studies show that the powers of the proposed tests are higher than that of Stone's test over all the alternatives considered. The proposed tests are illustrated with hypothetical data as well as simulated data to be expected in an epidemiological study currently in progress regarding an excess risk of perinatal undesirable outcomes near municipal solid waste incinerators in Japan.

Cluster Analysis↗

PubMed2004

Limitations of screening tests for the detection of Chlamydia trachomatis in asymptomatic adolescent and young adult women.

OBJECTIVE: The purpose of this study was to examine the performance of different test types, specimen sources, and collection methods for screening of genital Chlamydia trachomatis infection in young women. STUDY DESIGN: Asymptomatic women aged 16 to 25 years collected their own vaginal swabs and a first-voided urine specimen; a clinician collected urethral, vaginal, and endocervical swabs for culture and nucleic acid amplification tests, polymerase chain reaction and ligase chain reaction. A positive culture, 2 positive nucleic acid amplification tests, or 1 positive nucleic acid amplification test confirmed by a separate nested polymerase chain reaction comprised the criterion standard to define a C. trachomatis-infected woman. RESULTS: The prevalence of C. trachomatis was 22% (30/139 women). All 9 test results were available for 126 participants (91%). Sensitivities were comparable for polymerase chain reaction and ligase chain reaction (52%-63%), except for urine polymerase chain reaction (44%), and were lower for culture (22%-37%); specificities were 99% to 100%, except for urine ligase chain reaction (91%). Positive predictive values were >93%, except for urine ligase chain reaction (65%); negative predictive values were 83% to 91%. Combining nucleic acid amplification test results from 2 different specimens improved sensitivities without compromising specificity. CONCLUSION: When C. trachomatis infection was defined by multiple tests from different specimen sources, the sensitivity of any 1 test from a single specimen source was lower than generally reported. The limitations of the use of a single test to identify C. trachomatis infection should be considered when test type, specimen source, and collection method for screening young women is being determined.

Adolescent↗

PubMed2003

Using ANOVA for gene selection from microarray studies of the nervous system.

Methods are presented for detecting differential expression using statistical hypothesis testing methods including analysis of variance (ANOVA). Practicalities of experimental design, power, and sample size are discussed. Methods for multiple testing correction and their application are described. Instructions for running typical analyses are given in the R programming environment. R code and the sample data set used to generate the examples are available at http://microarray.cpmc.columbia.edu/pavlidis/pub/aovmethods/.

Analysis of Variance↗

PubMed2004

A global test for groups of genes: testing association with a clinical outcome.

MOTIVATION: This paper presents a global test to be used for the analysis of microarray data. Using this test it can be determined whether the global expression pattern of a group of genes is significantly related to some clinical outcome of interest. Groups of genes may be any size from a single gene to all genes on the chip (e.g. known pathways, specific areas of the genome or clusters from a cluster analysis). RESULT: The test allows groups of genes of different size to be compared, because the test gives one p-value for the group, not a p-value for each gene. Researchers can use the test to investigate hypotheses based on theory or past research or to mine gene ontology databases for interesting pathways. Multiple testing problems do not occur unless many groups are tested. Special attention is given to visualizations of the test result, focussing on the associations between samples and showing the impact of individual genes on the test result. AVAILABILITY: An R-package globaltest is available from http://www.bioconductor.org

Algorithms↗

PubMed1989

Papanicolaou test coverage without a cytology registry.

Because of problems in following women over time, it is difficult to assess the degree of Papanicolaou test coverage among the general population. In a region with no cytology register or recall system, the authors used data from Manitoba's universal health insurance plan to determine the actual number of women tested and the number of tests per woman from 1970 to 1984 inclusive. By cross-sectional analysis, the proportion screened annually was found to be highest for women aged 25-34 years (50-57%) and decreased with increasing age. The proportion screened annually for women over 25 remained essentially unchanged over the 15 years (34-39%). From a probability sample of women aged 35-64 years (n = 17,711), it was found that 91% had at least one test and 78% had three or more tests over 15 years. Untested women tended to be single, older, and from rural or remote areas. To assess multiple testing, the authors used the cross-sectional data to determine the number of women with two or more tests per year. About 4% of women had two or more tests annually, and 60% of these were accompanied by a diagnosis suggestive of an abnormal gynecologic condition. On the basis of published recommended schedules for Papanicolaou testing, the authors conclude that the widespread testing in Manitoba shows that the voluntary system has been working fairly well. High rates of coverage were achieved but with a degree of overtesting for some women.

Age Factors↗

PubMed2004

Microarray data analysis: from hypotheses to conclusions using gene expression data.

We review several commonly used methods for the design and analysis of microarray data. To begin with, some experimental design issues are addressed. Several approaches for pre-processing the data (filtering and normalization) before the statistical analysis stage are then discussed. A common first step in this type of analysis is gene selection based on statistical testing. Two approaches, permutation and model-based methods are explained and we emphasize the need to correct for multiple testing. Moreover, powerful approaches based on gene sets are mentioned. Clustering of either genes or samples is frequently performed when analyzing microarray data. We summarize the basics of both supervised and unsupervised clustering (classification). The latter may be of use for creating diagnostic arrays, for example. Construction of biological networks, such as pathways, is a statistically challenging but complex task that is a relatively new development and hence mentioned only briefly. We finish with some remarks on literature and software. The emphasis in this paper is on the philosophy behind several statistical issues and on a critical interpretation of microarray related analysis methods.

Cluster Analysis↗

PubMed1975

Decisive factors in the tolbutamide controversy.

No increased mortality trend attributable to tolbutamide is shown by an analysis of variance on logit-transformed data from the University Group Diabetes Program (UGDP) study. The UGDP's controversial finding of an increased rate with mortality subgrouped by "cardiovascular" causes is confirmed by the Biometric Committee's report, with reservations that failed to include overriding decisive factors. The basic problem is that inspected data set up the hypothesis (the increased cardiovascular mortality), and that the same data were used to test the hypothesis, so that resulting probability values no longer have the usual meaning. The problem was compounded by multiple testing of the data without adjusting the probability levels. When cardiovascular deaths were redefined as myocardial infarcts and sudden deaths, in an attempt to test a proposed etiologic inotropic hypothesis, no significant increase in cardiovascular mortality was found.

Age Factors↗

PubMed2000

Neonatal sepsis and death after multiple courses of antenatal betamethasone therapy.

OBJECTIVE: This study was undertaken to compare the effects of single versus multiple courses of betamethasone therapy on the frequencies of neonatal outcomes and perinatal infectious morbidity among singleton pregnancies complicated by preterm delivery. STUDY DESIGN: We performed a nonconcurrent prospective analysis of singleton pregnancies delivered between 24 and 34 weeks' gestation after antenatal betamethasone exposure. Patients were categorized into two groups according to betamethasone exposure: (1) two 12-mg doses in a 24-hour interval on admission (single-course group) and (2) repeated dosing after the initial single course (multiple-course group). All patients received prophylactic antibiotics for group B streptococci. Any patients with ruptured membranes for >24 hours before delivery were excluded. Data were analyzed with the Student t test, the chi(2) test, and the Fisher exact test. Multiple logistic regression analyses were performed to examine the effect of each steroid dosing regimen on early-onset neonatal sepsis and neonatal death. P <.05 was considered significant for all 2-tailed tests. RESULTS: A total of 453 patients were included, with 267 in the single-course group and 186 in the multiple-course group. The two groups were similar with respect to maternal demographic characteristics, gestational age at delivery, mode of delivery, birth weight, and maternal group B streptococcal colonization. Multiple courses were significantly associated with early-onset neonatal sepsis (odds ratio, 5.00; 95% confidence interval, 1.3-23. 2), chorioamnionitis (odds ratio, 9.96; 95% confidence interval, 2. 1-64.6), endometritis (odds ratio, 3.61; 95% confidence interval, 1. 7-8.1), and neonatal death (odds ratio, 2.92; 95% confidence interval, 1.3-6.9). The frequencies of the other neonatal outcomes analyzed, including respiratory distress syndrome and grade III or IV intraventricular hemorrhage, were similar between the 2 groups. Multiple logistic regression analyses confirmed that multiple courses of antenatal betamethasone were independently associated with early-onset neonatal sepsis (odds ratio, 1.25; 95% confidence interval, 1.1-1.9) and neonatal death (odds ratio, 1.70; 95% confidence interval, 1.1-1.9). CONCLUSIONS: Multiple courses of antenatal betamethasone are associated with increased risks of perinatal infectious morbidity and neonatal death.

Adult↗