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Results for “association testing”

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At least 235 records · Page 13Linked to original sources
PubMed2005

Genomic screening and replication using the same data set in family-based association testing.

The Human Genome Project and its spin-offs are making it increasingly feasible to determine the genetic basis of complex traits using genome-wide association studies. The statistical challenge of analyzing such studies stems from the severe multiple-comparison problem resulting from the analysis of thousands of SNPs. Our methodology for genome-wide family-based association studies, using single SNPs or haplotypes, can identify associations that achieve genome-wide significance. In relation to developing guidelines for our screening tools, we determined lower bounds for the estimated power to detect the gene underlying the disease-susceptibility locus, which hold regardless of the linkage disequilibrium structure present in the data. We also assessed the power of our approach in the presence of multiple disease-susceptibility loci. Our screening tools accommodate genomic control and use the concept of haplotype-tagging SNPs. Our methods use the entire sample and do not require separate screening and validation samples to establish genome-wide significance, as population-based designs do.

Asthma↗
PubMed2002

Association testing by DNA pooling: an effective initial screen.

With an ever-increasing resource of validated single-nucleotide polymorphisms (SNPs), the limiting factors in genome-wide association analysis have become genotyping capacity and the availability of DNA. We provide a proof of concept of the use of pooled DNA as a means of efficiently screening SNPs and prioritizing them for further study. This approach reduces the final number of SNPs that undergo full, sample-by-sample genotyping as well as the quantity of DNA used overall. We have examined 15 SNPs in the cholesteryl ester transfer protein (CETP) gene, a gene previously demonstrated to be associated with serum high-density lipoprotein cholesterol levels. The SNPs were amplified in two pools of DNA derived from groups of individuals with extremely high and extremely low serum high-density lipoprotein cholesterol levels, respectively. P values <0.05 were obtained for 14 SNPs, supporting the described association. Genotyping of the individual samples showed that the average margin of error in frequency estimate was approximately 4% when pools were used. These findings clearly demonstrate the potential of pooling techniques and their associated technologies as an initial screen in the search for genetic associations.

Adolescent↗
PubMed1975

A positive ethanol gelation test associated with high plasma fibrinogen concentration - evidence for soluble fibrin. An experimental study in rabbits.

By infusion of large amounts of human fibrinogen into rabbits, the ethanol gelation test turned positive at various plasma concentrations of fibrinogen, depending on the fibrinogen preparation used, and on individual differences among the animals. After incubation of the fibrinogen preparation in the cold the precipitated material gave a positive ethanol gelation test at lower fibrinogen concentration whereas the ethanol gelation test remained negative in the supernatant at a higher fibrinogen level than that of the starting material. It is concluded that the finding of a positive ethanol gelation test is not due to the fibrinogen concentration per se. Most likely the test becomes positive due to the presence of soluble fibrin in the commercial preparations.

Animals↗
PubMed2006

High-density haplotype structure and association testing of the insulin-degrading enzyme (IDE) gene with type 2 diabetes in 4,206 people.

The insulin-degrading enzyme is responsible for the intracellular proteolysis of insulin. Its gene IDE is located on chromosome 10, in an area with suggestive linkage to type 2 diabetes and related phenotypes. Due to the impact of genetic variants of this gene in rodents and the function of its protein product, it has been proposed as a candidate gene for type 2 diabetes. Various groups have explored the role of the common genetic variation of IDE on insulin resistance and reported associations of various single nucleotide polymorphisms (SNPs) and haplotypes on both type 2 diabetes and glycemic traits. We sought to characterize the haplotype structure of IDE in detail and replicate the association of common variants with type 2 diabetes, fasting insulin, fasting glucose, and insulin resistance. We assessed linkage disequilibrium, selected single-marker and multimarker tags, and genotyped these markers in several case-control and family-based samples totalling 4,206 Caucasian individuals. We observed no statistically significant evidence of association between single-marker or multimarker tests in IDE and type 2 diabetes. Nominally significant differences in quantitative traits are consistent with statistical noise. We conclude that common genetic variation at IDE is unlikely to confer clinically significant risk of type 2 diabetes in Caucasians.

Diabetes Mellitus, Type 2↗
PubMedDate not supplied

A review of the special tests associated with shoulder examination. Part II: laxity, instability, and superior labral anterior and posterior (SLAP) lesions.

This is the second of a two-part article describing the various tests that have been used to examine the shoulder to find and treat problems in that area. Part I of this article (January/February 2003, pages 154-160) focused on tests used to examine rotator cuff abnormalities. This article attempts to clarify the tests of laxity, instability, and the superior labral anterior and posterior (SLAP) lesions by presenting them as described by the original authors, with the additional aim of providing a source for those wishing to refresh their knowledge without the need to refer to the original source material.

Humans↗
PubMed2006

Are transient increases in blood pressure during the treadmill stress test associated with headache?

We aimed to investigate whether transient increases in blood pressure (BP) are associated with headache, by provoking hypertension in 50 non-hypertensive cephalalgia sufferers (Ce), 50 hypertensive cephalalgia sufferers (HyCe) and 50 healthy subjects (C) with a treadmill stress test. Occurrence of headache among groups did not differ (P = 0.81); however, women developed headache more frequently than men (P < 0.0001). The 35 individuals who developed headache during the test compared with those who did not (regardless of their original group) had higher absolute diastolic BP and higher absolute and relative diastolic BP increase during the test (P < 0.0001). HyCe patients that developed headache had higher diastolic BP than those that did not (P < 0.002). For each group, the absolute/relative mean increases of systolic/diastolic BP did not differ between patients that developed headache and those that did not excepting relative diastolic BP increase in Ce (28% vs. 15%, P = 0.006). The appearance of headache during dynamic exercise is not associated with a history of headache or hypertension. In non-hypertensive cephalalgia sufferers, relative diastolic BP increases of >27% are associated with headache attacks whereas in HyCe sufferers absolute diastolic BP values may be more important.

Adult↗
PubMed1982

Flavor-toxicosis associations: tests of three hypotheses of long delay learning.

Rats were prepared with gastric cannulas and esophageal fistulas to assess the contribution of taste and smell, postingestinal stimuli, and the combination of the two in forming flavor-toxicosis associations. Groups were either given sugar water to drink, a stomach intubation of sugar water, both sugar water to drink and a stomach intubation of sugar water, or not given sugar water. The experimental and pseudo-conditioning control animals were given a LiCl injection and the control animals were given a NaCl injection one hour later. They were tested for drinking of sugar water the next day. It was found that taste and smell are the primary stimuli for forming food aversions. Furthermore, postingestional stimuli are not sufficient to produce this type of learning.

Animals↗
PubMed1989

[The role of coagulase negative staphylococci in mixed infections: association testing as an in vitro model].

Infections due to coagulase negative staphylococci (CNS) are of growing concern mainly in patients hospitalized in intensive care units (ICU). The ability of CNS to adhere and to grow on plastic devices and resistance to many antibiotics, including oxacillin, contributes to their pathogenicity. Using the computer assisted system of the Medical Microbiology Department, the incidences of different pathogens and the coincidence of CNS with other bacteria were evaluated in a surgical department. Staphylococcus aureus revealed to be the predominant pathogen; however, CNS showed an increasing incidence in wound specimens and blood cultures of patients on the ICU. Coincidence of CNS with S. aureus and the nine most frequent species of gram negative bacteria could be shown in 6%. To investigate the influence of beta-lactamases produced by CNS in mixed infections, association experiments were performed. Association means a controlled growth of two or even more bacteria in a susceptibility testing system, either a broth dilution method or an automated broth disk elution method (Cobas Bact). The association experiments showed a significant increase of amoxicillin MIC's of the pathogen associated with CNS. Addition of clavulanic acid restored activity of amoxicillin. It could be shown that in mixed infections CNS may contribute to the failure of antibiotic regimens by production of beta-lactamases.

Bacteriological Techniques↗
PubMed2006

Are scores on balance screening tests associated with mobility in older adults?

PURPOSE: To examine associations between measures of static and dynamic balance and performance of mobility tasks in older adults. METHODS: A cross-sectional analysis from 95 community dwelling participants (mean age 80.9 years, range 65 -03 years). Participants performed tests of static (tandem stance) and dynamic (360 degrees turn) balance and mobility (walking speed and timed chair rise). Associations among balance and mobility measures were examined using correlation and logistic regression. RESULTS: Static and dynamic balance were moderately associated (r = -.462). Relationships between dynamic balance and mobility were stronger than those between static balance and mobility. The association between dynamic balance and walking speed was particularly strong (r = -.701 ). Using logistic regression, age, and balance performance were significant predictors for outcomes of walking speed (dichotomized to < .0 m/s, >/= .0 m/s), and timed chair rise (dichotomized to </= 3.6 s, > 3.6 s). Faster 360 degrees turn times were independently associated with faster walking speed and chair rise time. CONCLUSION: Mobility tasks require both dynamic and static balance. As falls are a major health risk for older adults, including brief assessments of dynamic and static balance in the examination of older adults provides valuable information about physical function and mobility.

Aged↗
PubMedDate not supplied

Reliability of the pretransfusion bedside compatibility test: association with transfusion practice and training.

BACKGROUND: The utility of a pretransfusion bedside blood compatibility protocol to decrease immunohemolytic accidents has been questioned for years. STUDY DESIGN AND METHODS: The reliability of a standard bedside ABO compatibility test was evaluated with a stratified random sample of 48 nurses who performed agglutination testing by using Bristol cards, interpreted compatibility, and decided whether to transfuse red cells for 12 randomly and blindly selected donor-and-recipient blood sample pairs. An expert judged technical performance and the interpretation of each card. RESULTS: Erroneous decisions occurred in 18.2 percent of 576 tests, including 12 decisions to transfuse incompatible blood. Errors involved both testing protocols and the interpretation of compatibility. Anti-A and anti-B were detected with 92.8-percent sensitivity and 95.9-percent specificity. The expert judged 17.7 percent of tests to be technically inadequate, most often because of the application of excess blood to the card and a lack of rotation of the card. Testing errors (16.1% of tests) were significantly linked to infrequent transfusion activity by the nursing service, inexperience, and insufficient training. Compatibility misinterpretation occurred in 14.6 percent of the tests and was significantly linked to the nurses' infrequent transfusion activity, inexperience, insufficient training, lack of practical experience, and confusion regarding the use of ABO-compatible but not identical blood. CONCLUSION: Bedside pretransfusion compatibility determination should not be considered a reliable supplemental safety procedure in the hands of inexperienced and insufficiently trained operators.

ABO Blood-Group System↗
PubMed2004

High-throughput association testing on DNA pools to identify genetic variants that confer susceptibility to acute myeloid leukemia.

We have evaluated the use of allele-specific PCR (AS PCR) on DNA pools as a tool for screening inherited genetic variants that may be associated with risk of adult acute myeloid leukemia (AML). Two DNA pools were constructed, one of 444 AML cases, and another of 823 matched controls. The pools were validated using individual genotyping data for GSTP1 and LTalpha variants. Allele frequencies for variants in GSTP1 and LTalpha were estimated using quantitative AS PCR, and when compared to individual genotyping data, a high degree of concordance was seen. AS primer pairs were designed for nine candidate genetic variants in DNA repair and cell cycle/apoptotic regulatory genes, including Cyclin D1 [codon 870 splice site variant (A>G)]; BRCA1, P871L; ERCC2, K751Q; FAS -1377 (G>A); hMLH1 -93 (G>A) and V219I; p21, S31R; and the XRCC1 R194W and R399Q variants. For six of these assays, there was at least 95% concordance between AS PCR genotyping and an alternative approach carried out on individual samples. Furthermore, these six AS PCR assays all accurately estimated allele frequencies in the pools that had been calculated using individual genotyping data. A significant disease association was seen with AML for the -1377 variant in FAS (odds ratio 1.76, 95% confidence interval 1.26-2.44). These data suggest that quantitative AS PCR can be used as an efficient screening technique for disease associations of genetic variants in DNA pools made from case-control studies.

Base Sequence↗