Score tests in a generalized linear model with surrogate covariates

We consider generalized linear models where a predictor is measured with error. The efficient score test for the effect of that predictor depends on the regression of the true predictor on its observed surrogate. Using validation data, we estimate the regression by nonparametric techniques. The resulting semiparametric score test is shown to be nearly asymptotically efficient.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29852/1/0000199.pd

A reduced complexity numerical method for optimal gate synthesis

Although quantum computers have the potential to efficiently solve certain problems considered difficult by known classical approaches, the design of a quantum circuit remains computationally difficult. It is known that the optimal gate design problem is equivalent to the solution of an associated optimal control problem, the solution to which is also computationally intensive. Hence, in this article, we introduce the application of a class of numerical methods (termed the max-plus curse of dimensionality free techniques) that determine the optimal control thereby synthesizing the desired unitary gate. The application of this technique to quantum systems has a growth in complexity that depends on the cardinality of the control set approximation rather than the much larger growth with respect to spatial dimensions in approaches based on gridding of the space, used in previous literature. This technique is demonstrated by obtaining an approximate solution for the gate synthesis on $SU(4)$- a problem that is computationally intractable by grid based approaches.Comment: 8 pages, 4 figure

Fracture Risk in Men With Congestive Heart Failure Risk Reduction With Spironolactone

ObjectivesThe purpose of this study was to determine whether spironolactone use is associated with fractures in men with congestive heart failure (CHF).BackgroundIn rats with aldosteronism, spironolactone preserves skeletal strength. However, in humans, the relationship of spironolactone to fractures is not known.MethodsThe medical records of all male patients with CHF from 1999 to 2005 treated at the Veterans Affairs Medical Center, Memphis, Tennessee, were reviewed (n = 4,735). Odds ratios with 95% confidence intervals of having a fracture associated with spironolactone use were estimated using conditional logistic regression.ResultsWe identified 167 cases with a single-incident fracture and matched these by age and race to 668 control subjects without fractures. After adjustment for covariates, spironolactone use was inversely associated with total fracture (odds ratio: 0.575; 95% confidence interval: 0.346 to 0.955, p = 0.0324).ConclusionsThe use of spironolactone is inversely associated with fractures in men with CHF

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Score tests in a generalized linear model with surrogate covariates

We consider generalized linear models where a predictor is measured with error. The efficient score test for the effect of that predictor depends on the regression of the true predictor on its observed surrogate. Using validation data, we estimate the regression by nonparametric techniques. The resulting semiparametric score test is shown to be nearly asymptotically efficient.Generalized linear model nonparametric regression score test

Semiparametric quasilikelihood and variance function estimation in measurement error models

We consider a quasilikelihood/variance function model when a predictor X is measured with error and a surrogate W is observed. When in addition to a primary data set containing (Y,W) a validation data set exists for which (X,W) is observed, we can (i) estimate the first and second moments of the response Y given W by kernel regression; (ii) use quasilikelihood and variance function techniques to estimate the regression parameters as well as variance structure parameters. The estimators are shown to be asymptotically normally distributed, with asymptotic variance depending on the size of the validation data set and not on the bandwith used in the kernel estimates. A more refined analysis of the asymptotic covariance shows that the optimal bandwidth converges to zero at the rate n-.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30707/1/0000353.pd

Clinical Risk Factors For Central Line Associated Venous Thrombosis (CLAVT) In Children

ABSTRACTBackground: Identifying risk factors related to Central Venous Line (CVL) placement could potentially minimize Central Line-Associated Venous Thrombosis (CLAVT). We sought to identify the clinical factors associated with CLAVT in children. Methods: Over a 3-year period, 3,733 CVLs were placed at a tertiary-care children’s hospital. Data were extracted from the electronic medical records of patients with clinical signs and symptoms of venous thromboembolism (VTE), diagnosed using Doppler ultrasonography and/or echocardiography. Statistical analyses examined differences in CLAVT occurrence between groups based on patient and CVL characteristics (type, brand, placement site, and hospital unit). Results: Femoral CVL placement was associated with greater risk for developing CLAVT (OR 11.1, 95% CI 3.9-31.6, p<0.0001). CVLs placed in the NICU were also associated with increased CLAVT occurrence (OR 5.3, 95% CI 2.1-13.2, p=0.0003). CVL brand was also significantly associated with risk of CLAVT events. Conclusion: Retrospective analyses identified femoral CVL placement and catheter type as independent risk factors for CLAVT, suggesting increased risks due to mechanical reasons. Placement of CVLs in the NICU also led to an increased risk of CLAVT, suggesting that small infants are at increased risk of thrombotic events. Alternative strategies for CVL placement, thromboprophylaxis, and earlier diagnosis may be important for reducing CLAVT events