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At least 289 records · Page 16Linked to original sources
PubMed1993

Record linkage to conduct an epidemiologic study on the association of rheumatoid arthritis and lymphoma in the Province of Saskatchewan, Canada.

The objective of this effort was to assess the utility of the large automated database in Saskatchewan as a resource for pharmacoepidemiologic studies. To this end a study was undertaken to test the hypothesis that rheumatoid arthritis (RA) increases the risk of cancer, especially lymphoma. This was done by performing a retrospective cohort study based on record linkage data from Saskatchewan Health. From hospital discharge diagnoses in the hospital file an exposed group (RA) and two comparison groups matched to the RA group by age and sex were identified: (1) the RA group consisted of people with a discharge diagnosis of rheumatoid arthritis; (2) the osteoarthritis (OA) group consisted of people with OA discharge diagnoses; and (3) a comparison (CN) group consisted of hospitalized people with no discharge diagnoses of arthritis. Drug exposures were determined by linkage with the Prescription Drug File, cancer outcomes were determined by linkage with the Cancer Foundation file, and length of eligibility in the health plan and demographics information were determined by linkage with the registration file. The data were checked for quality of linkages across files and consistency with study definitions. Of 13,333 identified subjects, 2.8% were excluded because of apparent incorrect assignment to study group or age group or because of ineligibility in health plan during the study period. In order to decrease the possibility of misclassification of exposure (rheumatoid arthritis), hospital discharge diagnoses were used to exclude subjects with any inflammatory rheumatic diseases (IRD) from the CN (7.8%) and OA (8.3%) groups and subjects with IRD other than rheumatoid arthritis (4.6%) from the RA group. To decrease selection bias, those who had cancer within 1 year of enrollment (to exclude those in hospital because of symptoms of undiagnosed cancer) were excluded. Because RA subjects hospitalized by a rheumatologist were most likely to have valid rheumatoid arthritis diagnoses, each analysis was run twice: once with the entire RA group (N = 1210) and once with those in the RA group who were rheumatologist-hospitalized (N = 646). Logistic regression of incidence was used to control for age, sex, and use of individual disease-modifying anti-rheumatoid drugs (DMARDs). For the rheumatologist-hospitalized RA group compared to the CN group, a significant 4-fold greater risk for lymphoma/myeloma was detected when DMARD use was not controlled for, and a 3.4-fold increase in risk was detected even when use of individual DMARDs was controlled for.(ABSTRACT TRUNCATED AT 400 WORDS)

Arthritis, Rheumatoid↗
PubMed1983

On the genetic length of the short arm of the human X chromosome.

Published estimates of the length of the human X chromosome are unreliable because they are based on scanty linkage data and complex assumptions about the frequency and distribution of chiasmata in female meiosis. In recent months we have established linkage between restriction fragment length polymorphisms (RFLPs) and several genes on the short arm of the X chromosome. These and previous data can be combined to construct a continuous linkage map spanning the short arm from the Xg gene to the centromere. They suggest that the genetic length of the Xg-Xcen segment may be in the order of 75-90 cM.

Chromosome Mapping↗
PubMed2002

High resolution mapping of quantitative trait loci by linkage disequilibrium analysis.

Two methods, linkage analysis and linkage disequilibrium (LD) mapping or association study, are usually utilised for mapping quantitative trait loci (QTL). Linkage mapping is appropriate for low resolution mapping to localise trait loci to broad chromosome regions within a few cM (<10 cM), and is based on family data. Linkage disequilibrium mapping, on the other hand, is useful in high resolution or fine mapping, and is based on both population and family data. Using only one marker, one may carry out single-point linkage analysis and linkage disequilibrium mapping. Using two or more markers, it is possible to flank the QTL by multipoint analysis. The development and thus availability of dense marker maps, such as single nucleotide polymorphisms (SNP) in human genome, presents a tremendous opportunity for multipoint fine mapping. In this article, we propose a regression approach of mapping QTL by linkage disequilibrium mapping based on population data. Assuming that two marker loci flank one quantitative trait locus, a two-point linear regression is proposed to analyse population data. We derive analytical formulas of parameter estimations, and non-centrality parameters of appropriate tests of genetic effects and linkage disequilibrium coefficients. The merit of the method is shown by the power calculation and comparison. The two-point regression model can capture much more linkage and linkage disequilibrium information than that derived when only one marker is used. For a complex disease with heritability h(2)> or =0.15, a study with sample size of 250 can provide high power for QTL detection under moderate linkage disequilibria.

Chromosome Mapping↗
PubMed2006

High-cost users of hospital beds in Western Australia: a population-based record linkage study.

OBJECTIVE: To describe how high-cost users of inpatient care in Western Australia differ from other users in age, health problems and resource use. DESIGN AND DATA SOURCES: Secondary analysis of hospital data and linked mortality data from the WA Data Linkage System for 2002, with cost data from the National Hospital Cost Data Collection (2001-02 financial year). OUTCOME MEASURES: Comparison of high-cost users and other users of inpatient care in terms of age, health profile (major diagnostic category) and resource use (annualised costs, separations and bed days). RESULTS: Older high-cost users (> or = 65 years) were not more expensive to treat than younger high-cost users (at the patient level), but were costlier as a group overall because of their disproportionate representation (n = 8466; 55.9%). Chronic stable and unstable conditions were a key feature of high-cost users, and included end stage renal disease, angina, depression and secondary malignant neoplasms. High-cost users accounted for 38% of both inpatient costs and inpatient days, and 26% of inpatient separations. CONCLUSION: Ageing of the population is associated with an increase in the proportion of high-cost users of inpatient care. High costs appear to be needs-driven. Constraining high-cost inpatient use requires more focus on preventing the onset and progression of chronic disease, and reducing surgical complications and injuries in vulnerable groups.

Adolescent↗
PubMedDate not supplied

A conservative viewpoint on linkage in Alzheimer's disease.

Linkage data in Alzheimer's disease have not firmly established a genetic locus on chromosome 21 in early onset disease families. There is little or no support for a chromosome 21 locus in late onset families. Differences in the selection of families and the analysis of data accounts for the differences in interpretation. The actual location of a genetic locus (or loci) for Alzheimer's disease in the human genome will not be influenced by this controversy; more data from exclusion mapping and the use of several methods of linkage analysis will answer current questions.

Alzheimer Disease↗
PubMed2002

A statistical method for identification of polymorphisms that explain a linkage result.

Suppose that many polymorphic sites have been identified and genotyped in a region showing strong linkage with a trait. A key question of interest is which site (or combination of sites) in the region influences susceptibility to the trait. We have developed a novel statistical approach to this problem, in the context of qualitative-trait mapping, in which we use linkage data to identify the polymorphic sites whose genotypes could fully explain the observed linkage to the region. The information provided by this analysis is different from that provided by tests of either linkage or association. Our approach is based on the observation that if a particular site is the only site in the region that influences the trait, then-conditional on the genotypes at that site for the affected relatives-there should be no unexplained oversharing in the region among affected individuals. We focus on the affected sib-pair study design and develop test statistics that are variations on the usual allele-sharing methods used in linkage studies. We perform hypothesis tests and derive a confidence set for the true causal polymorphic site, under the assumption that there is only one site in the region influencing the trait. Our method is appropriate under a very general model for how the site influences the trait, including epistasis with unlinked loci, correlated environmental effects within families, and gene-environment interaction. We extend our method to larger sibships and apply it to an NIDDM1 data set.

Alleles↗
PubMed2000

Familial typical migraine: significant linkage and localization of a gene to Xq24-28.

In a previous study we found evidence for an X-linked genetic component for familial typical migraine in two large Australian white pedigrees, designated MF7 and MF14. Significant excess allele sharing was indicated by nonparametric linkage (NPL) analysis using GENEHUNTER (P=0.031 and P=0.012, respectively), with a combined analysis of the two pedigrees showing further increased evidence for linkage, producing a maximum NPL score of 2.87 (P=0.011 ) at DXS 1123 on Xq27. The present study was aimed at refining the localization of the migraine X-chromosomal component by typing additional markers, performing haplotype analysis and applying a more powerful technique in the analysis of linkage data from these two pedigrees. Results from the haplotype analyses, coupled with linkage analyses that produced a peak GENEHUNTER-PLUS LOD* score of 2.388 (P=0.0005), provide compelling evidence for the presence of a migraine susceptibility locus on chromosome Xq24-28.

Chromosome Mapping↗
PubMed1996

Linkage of frontotemporal dementia to chromosome 17: clinical and neuropathological characterization of phenotype.

Frontotemporal dementia is a behavioral disorder of insidious onset and variable progression. Clinically, its early features reflect frontal lobe dysfunction characterized by personality change, deterioration in memory and executive functions, and stereotypical and perseverative behaviors. Pathologically, there is degeneration of the neocortex and subcortical nuclei, without distinctive features such as plaques, neurofibrillary tangles, or Pick or Lewy bodies. Within-family variation in neuropathology and clinical phenotype is observed. In cases where family aggregation is observed, it is inherited as an autosomal dominant, age-dependent disorder. Family studies recently have identified two dementia loci: chromosome 17 for disinhibition-dementia-parkinsonism-amyotrophic complex and pallido-ponto-nigral degeneration and chromosome 3 for familial nonspecific dementia. We describe a family (DUK1684) with clinically and neuropathologically confirmed, autosomal dominant, non-Alzheimer disease dementia. Linkage analysis of this family showed evidence for linkage to chromosome 17q21, with a multipoint location score (log10) of 5.52. A comparison of the clinical and pathological features in DUK1684 with those of the other chromosome 17-linked families, together with the linkage data, suggests that these families are allelic. These studies emphasize that genetic linkage analysis remains a useful tool for differentiating disease loci in clinically complex traits.

Age of Onset↗
PubMed2006

A posterior probability of linkage-based re-analysis of schizophrenia data yields evidence of linkage to chromosomes 1 and 17.

OBJECTIVE: Linkage analysis using 22 Canadian pedigrees identified a promising schizophrenia candidate region on 1q23 with a maximum 2-point HLOD under a recessive model of 5.8 [Brzustowicz et al. 2000]. In the current study, we revisited this data set using a Bayesian linkage analysis technique, namely the posterior probability of linkage (PPL). METHODS: The PPL has been developed as an alternative to traditional linkage analysis. It differs from both LOD scores and 'non-parametric' methods in that it directly measures the probability of linkage given the data, and incorporates prior genomic information. RESULTS: As expected, PPL results for 1q23 supported the previously observed linkage, with an estimated multipoint PPL of 99.7%. However, the PPL supported two further results: a second peak on chromosome 1 at 1p13 with a multipoint with PPL of 70% and a chromosome 17 marker (D17S784 at 17q25) with a multipoint PPL of 44%. CONCLUSIONS: The PPL-based analysis presented has the advantage over other likelihood-based linkage methods in that it avoids maximization and produces a less complex view of the strength of evidence for linkage.

Chromosomes, Human, Pair 1↗
PubMed1990

The linkage detection problem.

Linkage data in man are usually analysed on families lacking a full set of grandparents on the assumption that there is one locus relating to an abnormal phenotype, the test locus. The basic problems of establishing linkage of this locus to another locus, the marker locus, with a defined likelihood and of estimating the recombination fraction were resolved by Morton (1955). However, the likelihood ratio derived after estimating the most likely recombination fraction is widely misunderstood to be a direct measure of the likelihood of linkage while the bias of estimates conditional on some likelihood criterion derived from the same data is usually ignored. Since data are limited this tolerance of excessive confidence in detecting linkages and a consistent tendency to underestimate recombination fractions is justified but the expected errors are not small and they are readily magnified when multiple loci are involved. Multiple markers provide further opportunities for detecting false linkages although the corrections required are known. The problems imposed by multiple loci at which mutations lead to a common phenotype have so far had little consideration. As most proteins are multimers whose units are not necessarily coded for by neighbouring loci, and as disturbances to any of several enzymes acting in series may lead to similar consequences, the assumption of a one-to-one relationship between a locus and a phenotype will usually be wrong.

Animals↗
PubMed1990

A linkage map of endogenous murine leukemia proviruses.

Thirty endogenous proviruses belonging to the modified polytropic (Mpmv) class of murine leukemia virus (MLV) were identified by proviral-cellular DNA junction fragment segregation in several sets of recombinant inbred mice. Twenty-six Mpmv loci were mapped to chromosomal regions by matching proviral strain distribution patterns to those of previously assigned genes. Like other endogenous nonecotropic MLVs, Mpmv loci were present on several chromosomes in all strains examined. We pooled recombinant inbred strain linkage data from 110 MLV loci and selected marker genes in order to construct a chromosomal linkage map. Every mouse chromosome was found to harbor at least one proviral insertion, and several regions contained multiple integrations. However, the overall distribution of the 110 mapped proviruses did not deviate significantly from a random distribution. Because of their polymorphism in inbred strains of mice, and the ability to score as many as 57 proviruses per strain using only three hybridization probes, the nonecotropic MLVs mapped in common strains of mice offer a significant advantage over older methods (e.g., biochemical or individual restriction fragment polymorphisms) as genetic markers. These endogenous insertion elements should also be useful for assessing strain purity, and for studying the relatedness of common and not-so-common inbred strains.

Animals↗
PubMed1995

Diagnostic accuracy and linkage analysis: how useful are schizophrenia spectrum phenotypes?

OBJECTIVE: Numerous studies suggest that the nonschizophrenic relatives of schizophrenic patients exhibit psychiatric and other features that discriminate them from normal comparison subjects. These features have been put forth as "spectrum" phenotypes that may be variant manifestations of the schizophrenia genotype. However, most of these studies do not address a key measurement question: does the diagnostic accuracy of these spectrum classifications warrant their use in genetic linkage studies of schizophrenia? METHOD: The authors reviewed 30 studies of putative indicators of the schizophrenic genotype: schizotypal personality disorder, eye tracking dysfunction, attentional impairment, auditory evoked potentials, neurological signs, neuropsychological impairment, and allusive thinking. RESULTS: Although each of 42 measures of these indicators discriminated the relatives of schizophrenic patients from the normal comparison subjects, a diagnostic accuracy analysis suggested that only six of these would improve the informativeness of genetic linkage data. CONCLUSIONS: Many proposed spectrum phenotypes for schizophrenia may not be useful for linkage analysis because of high false positive rates (poor specificity). Future work aimed at describing and developing phenotypes for linkage analysis should assess the diagnostic accuracy of proposed measures.

Attention↗
PubMedDate not supplied

Statewide air medical transports for Massachusetts.

In 1997, the Massachusetts Department of Public Health (MDPH) established a process to centralize air medical transport information. This database is one of the first statewide, population-based sources for civilian rotary-wing air medical transports (U.S. Coast Guard, police, and military missions are not included). The purpose of this database is to facilitate MDPH review of air medical transport service utilization, with input from a multidisciplinary committee. This article discusses the challenges in producing uniform data from multiple service submissions and presents aggregate "baseline" utilization information for 1996. These data served as a starting point for later studies using data linkage. This indexed article is the first to report statewide, population-based data for all types of air medical helicopter transports. The only other indexed "statewide air medical transport" paper focused on scene transports to trauma centers in Pennsylvania. A previous article by the authors in the July-September 2000 Air Medical Journal provided an overview of air medical transports for fatal motor vehicle crashes for 1 region of the state.

Air Ambulances↗
PubMed1986

Genetics of esterases and 6-phosphogluconate dehydrogenase in the Anopheles maculatus complex.

Electromorphic variation for some esterases and 6-phosphogluconate dehydrogenase enzymes in the Anopheles maculatus complex is controlled by four loci which are unlinked to sex. Esterase loci are linked to each other: Est-1-36%-Est-4-16.5%-Est-3; but unlinked to Pgd-2. Linkage data were obtained by selfing the F1 generation from selected parents and analysing genotypes in the F2; the classical dihybrid-cross. The analysis consists of testing observed data for goodness of fit to a) ratios expected from Mendelian ratios without linkage and b) if they do not fit then computing a likely degree of linkage and computing expected ratios with such linkage for further tests. Confidence limits are given for the most likely levels of linkage. This method can provide useful information for population-genetic studies on anopheline mosquitoes, whose laboratory rearing is generally difficult. Through indirect evidence, the enzyme loci are correlated to polytene chromosomes. The esterases probably lie on chromosome three (polytene arms 3 and 4) and Pgd-2 on the second chromosome (arms 2 and 5).

Animals↗
PubMed1989

Robust methods for the detection of genetic linkage for quantitative data from pedigrees.

The robust method for detecting linkage developed by Haseman and Elston [The investigation of linkage between a quantitative trait and a marker locus. Behav Genet 2:3-19, 1972] for data from sib pairs is extended to any type of noninbred relative pair. The regression of the squared relative-pair trait difference on the estimated proportion of genes identical by descent (i.b.d.) at a marker locus is shown to depend upon the recombination fraction between the two loci; the regression coefficient is negative if the trait and marker loci are linked. A test for linkage based on data from any informative type of relative pair can thus be obtained by testing that this regression coefficient is less than zero. Formulae for the asymptotic power of such tests for linkage based upon independent relative pairs are developed. Results are also given for the special case in which the proportion of genes shared i.b.d. for relative pairs is known. Finally, a general algorithm is described that will incorporate all available pedigree data to calculate an estimate of the proportion of genes that a relative pair shares i.b.d. at a marker locus.

Genetic Linkage↗
PubMed1988

A procedure for linking psychosocial job characteristics data to health surveys.

A system is presented for linking information about psychosocial characteristics of job situations to national health surveys. Job information can be imputed to individuals on surveys that contain three-digit US Census occupation codes. Occupational mean scores on psychosocial job characteristics-control over task situation (decision latitude), psychological work load, physical exertion, and other measures-for the linkage system are derived from US national surveys of working conditions (Quality of Employment Surveys 1969, 1972, and 1977). This paper discusses a new method for reducing the biases in multivariate analyses that are likely to arise when utilizing linkage systems based on mean scores. Such biases are reduced by modifying the linkage system to adjust imputed individual scores for demographic factors such as age, education, race, marital status and, implicitly, sex (since men and women have separate linkage data bases). Statistics on the linkage system's efficiency and reliability are reported. All dimensions have high inter-survey reproducibility. Despite their psychosocial nature, decision latitude and physical exertion can be more efficiently imputed with the linkage system than earnings (a non-psychosocial job characteristic). The linkage system presented here is a useful tool for initial epidemiological studies of the consequences of psychosocial job characteristics and constitutes the methodological basis for the subsequent paper.

Decision Making↗
PubMed1993

Racial misclassification of American Indians: its effect on injury rates in Oregon, 1989 through 1990.

OBJECTIVES: We assessed the extent to which injury rates among American Indians in Oregon are underestimated owing to misclassification of race in a surveillance system. METHODS: The Oregon Injury Registry, a population-based surveillance system, was linked with the Indian Health Service patient registration file from Oregon, and injury rates for American Indians were calculated before and after correcting for racial misclassification. RESULTS: In 1989 and 1990, 301 persons in the Oregon registry were coded as American Indian. An additional 89 injured persons who were coded as a race other than American Indian in the registry were listed as American Indian in the Indian Health Service records. The age-adjusted annual injury rate for health service-registered American Indians was 6.9/1000, 68% higher than the rate calculated before data linkage. American Indian ancestry, female sex, and residence in metropolitan counties were associated with a higher likelihood of concordant racial classification in both data sets. CONCLUSION: Injury rates among American Indians in an Oregon surveillance system are substantially underestimated owing to racial misclassification. Linkage of disease registries and vital records with Indian Health Service records in other states may improve health-related data regarding American Indians.

Adult↗