Improved score tests in symmetric linear regression models

The class of symmetric linear regression models has the normal linear regression model as a special case and includes several models that assume that the errors follow a symmetric distribution with longer-than-normal tails. An important member of this class is the t linear regression model, which is commonly used as an alternative to the usual normal regression model when the data contain extreme or outlying observations. In this article, we develop second-order asymptotic theory for score tests in this class of models. We obtain Bartlett-corrected score statistics for testing hypotheses on the regression and the dispersion parameters. The corrected statistics have chi-squared distributions with errors of order O(n(-3/2)), n being the sample size. The corrections represent an improvement over the corresponding original Rao`s score statistics, which are chi-squared distributed up to errors of order O(n(-1)). Simulation results show that the corrected score tests perform much better than their uncorrected counterparts in samples of small or moderate size.

Three Bartlett-type corrections for score statistics in symmetric nonlinear regression models

We present simple matrix formulae for corrected score statistics in symmetric nonlinear regression models. The corrected score statistics follow more closely a chi (2) distribution than the classical score statistic. Our simulation results indicate that the corrected score tests display smaller size distortions than the original score test. We also compare the sizes and the powers of the corrected score tests with bootstrap-based score tests.

Measurement error models with a general class of error distribution

In general, the normal distribution is assumed for the surrogate of the true covariates in the classical error model. This paper considers a class of distributions, which includes the normal one, for the variables subject to error. An estimation approach yielding consistent estimators is developed and simulation studies reported.

Small-Sample Corrections for Score Tests in Birnbaum-Saunders Regressions

In this article, we deal with the issue of performing accurate small-sample inference in the Birnbaum-Saunders regression model, which can be useful for modeling lifetime or reliability data. We derive a Bartlett-type correction for the score test and numerically compare the corrected test with the usual score test and some other competitors.

Shwachman-Kulczycki score still useful to monitor cystic fibrosis severity

INTRODUCTION: The Shwachman-Kulczycki score was the first scoring system used in cystic fibrosis to assess disease severity. Despite its subjectivity, it is still widely used. OBJECTIVE: To study correlations among forced expiratory volume in one second (FEV1), chest radiography, chest computed tomography, 6-minute walk test, and Shwachman-Kulczycki score in patients with cystic fibrosis and to test whether the Shwachman-Kulczycki score is still useful in monitoring the severity of the disease. METHODS: A cross-sectional prospective study was performed to analyze the correlations (Spearman). Patients with clinically stable cystic fibrosis, aged 3-21 years, were included. RESULTS: 43 patients, 19F/24M, mean age 10.5 + 4.7 years, with a median Shwachman-Kulczycki score of 70 were studied. The median Brasfield and Bhalla scores were 17 and 10, respectively. The mean Z score for the 6-minute walk test was -1.1 + 1.106 and the mean FEV1 was 59 + 26 (as percentage of predicted values). The following significant correlations versus the Shwachman-Kulczycki score were found: FEV1 (r = 0.76), 6-minute walk test (r = 0.71), chest radiography (r = 0.71) and chest computed tomography (r = -0.78). When patients were divided according to FEV1, a statistically significantly correlation with the Shwachman-Kulczycki score was found only in patients with FEV1 <70% (r = 0.67). CONCLUSIONS: The Shwachman-Kulczycki score remains an useful tool for monitoring the severity of cystic fibrosis, adequately reflecting the functional impairment and chest radiography and tomography changes, especially in patients with greater impairment of lung function. When assessing patients with mild lung disease its limitations should be considered and its usefulness in such patients should be evaluated in larger populations.

Metabolic syndrome and dietary components are associated with coronary artery disease risk score in free-living adults: a cross-sectional study

Background: Coronary artery disease (CAD) is among the main causes of death in developed countries, and diet and lifestyle can influence CAD incidence. Objective: To evaluate the association of coronary artery disease risk score with dietary, anthropometric and biochemical components in adults clinically selected for a lifestyle modification program. Methods: 362 adults (96 men, 266 women, 53.9 +/- 9.4 years) fulfilled the inclusion criteria by presenting all the required data. The Framingham score was calculated and the IV Brazilian Guideline on Dyslipidemia and Prevention of Atherosclerosis was adopted for classification of the CAD risks. Anthropometric assessments included waist circumference (WC), body fat and calculated BMI (kg/m(2)) and muscle-mass index (MMI kg/m(2)). Dietary intake was estimated through 24 h dietary recall. Fasting blood was used for biochemical analysis. Metabolic Syndrome (MS) was diagnosed using NCEP-ATPIII (2001) criteria. Logistic regression was used to determine the odds of CAD risks according to the altered components of MS, dietary, anthropometric, and biochemical components. Results: For a sample with a BMI 28.5 +/- 5.0 kg/m(2) the association with lower risk (<10% CAD) were lower age (<60 years old), and plasma values of uric acid. The presence of MS within low, intermediary, and high CAD risk categories was 30.8%, 55.5%, and 69.8%, respectively. The independent risk factors associated with CAD risk score was MS and uric acid, and the protective factors were recommended intake of saturated fat and fiber and muscle mass index. Conclusion: Recommended intake of saturated fat and dietary fiber, together with proper muscle mass, are inversely associated with CAD risk score. On the other hand, the presence of MS and high plasma uric acid are associated with CAD risk score.

Quasiharmonic elastic constants corrected for deviatoric thermal stresses

The quasiharmonic approximation (QHA), in its simplest form also called the statically constrained (SC) QHA, has been shown to be a straightforward method to compute thermoelastic properties of crystals. Recently we showed that for noncubic solids SC-QHA calculations develop deviatoric thermal stresses at high temperatures. Relaxation of these stresses leads to a series of corrections to the free energy that may be taken to any desired order, up to self-consistency. Here we show how to correct the elastic constants obtained using the SC-QHA. We exemplify the procedure by correcting to first order the elastic constants of MgSiO(3) perovskite and MgSiO(3) postperovskite, the major phases of the Earth's lower mantle. We show that this first-order correction is quite satisfactory for obtaining the aggregated elastic averages of these minerals and their velocities in the lower mantle. This type of correction is also shown to be applicable to experimental measurements of elastic constants in situations where deviatoric stresses can develop, such as in diamond-anvil cells.

A score system for quality evaluation of RNA sequence tags: an improvement for gene expression profiling

Background: High-throughput molecular approaches for gene expression profiling, such as Serial Analysis of Gene Expression (SAGE), Massively Parallel Signature Sequencing (MPSS) or Sequencing-by-Synthesis (SBS) represent powerful techniques that provide global transcription profiles of different cell types through sequencing of short fragments of transcripts, denominated sequence tags. These techniques have improved our understanding about the relationships between these expression profiles and cellular phenotypes. Despite this, more reliable datasets are still necessary. In this work, we present a web-based tool named S3T: Score System for Sequence Tags, to index sequenced tags in accordance with their reliability. This is made through a series of evaluations based on a defined rule set. S3T allows the identification/selection of tags, considered more reliable for further gene expression analysis. Results: This methodology was applied to a public SAGE dataset. In order to compare data before and after filtering, a hierarchical clustering analysis was performed in samples from the same type of tissue, in distinct biological conditions, using these two datasets. Our results provide evidences suggesting that it is possible to find more congruous clusters after using S3T scoring system. Conclusion: These results substantiate the proposed application to generate more reliable data. This is a significant contribution for determination of global gene expression profiles. The library analysis with S3T is freely available at http://gdm.fmrp.usp.br/s3t/.S3T source code and datasets can also be downloaded from the aforementioned website.

Long life of Gauss-Bonnet corrected black holes

Dictated by the string theory and various higher dimensional scenarios, black holes in D > 4-dimensional space-times must have higher curvature corrections. The first and dominant term is quadratic in curvature, and called the Gauss-Bonnet (GB) term. We shall show that although the Gauss-Bonnet correction changes black hole's geometry only softly, the emission of gravitons is suppressed by many orders even at quite small values of the GB coupling. The huge suppression of the graviton emission is due to the multiplication of the two effects: the quick cooling of the black hole when one turns on the GB coupling and the exponential decreasing of the gray-body factor of the tensor type of gravitons at small and moderate energies. At higher D the tensor gravitons emission is dominant, so that the overall lifetime of black holes with Gauss-Bonnet corrections is many orders larger than was expected. This effect should be relevant for the future experiments at the Large Hadron Collider (LHC).

Bias-corrected Pearson estimating functions for Taylor`s power law applied to benthic macrofauna data

Estimation of Taylor`s power law for species abundance data may be performed by linear regression of the log empirical variances on the log means, but this method suffers from a problem of bias for sparse data. We show that the bias may be reduced by using a bias-corrected Pearson estimating function. Furthermore, we investigate a more general regression model allowing for site-specific covariates. This method may be efficiently implemented using a Newton scoring algorithm, with standard errors calculated from the inverse Godambe information matrix. The method is applied to a set of biomass data for benthic macrofauna from two Danish estuaries. (C) 2011 Elsevier B.V. All rights reserved.

Use of AST platelet ratio index (APRI Score) as an alternative to liver biopsy for treatment indication in chronic hepatitis C

Chronic hepatitis C (CHC) is one of the most important causes of chronic liver disease in the world, potentially resulting in cirrhosis, hepatocellular carcinoma, and the need for liver transplantation. Liver biopsy is currently performed before therapy indication. Although, it is the golden standard there are many reasons to avoid or delay the procedure. APRI Score is an easy, low cost and practice alternative method which was described as an alternative for assessing structural changes in chronic hepatitis C (CHC). The rationale of this study was to observe the accuracy of APRI Score in comparison to liver biopsy in 400 patients divided into two groups of 200 carriers (Validation and Experimental groups respectively) selected at random or according to liver fibrosis staging (METAVIR). The ROC curves showed a concordance among these two methods of 92% and 88.5% when 1.05 was the cut off (F3 and F4), and 87% and 83%, on 0.75 cut offs (F2-F4). The discordance in advanced fibrosis staging (F3 and F4) was only 16 (8%) and 22 (11%) out of 200 patients in the experimental and validation groups, respectively. In 26 (13%) out of 200 patients in the experimental group and 34 (17%) out of 200 patients in the validation group, there was discordance between APRI Score and liver biopsy in moderate and advanced fibrosis (F2-F4). In conclusion APRI is a serological marker that has satisfactory sensitivity and specificity together with a high predictive value and it can be useful either in the absence of a biopsy or to reduce the frequency with which biopsies need to be carried out to monitor the evolution of chronic hepatitis C and the right moment for treatment indication.

The Finnish Diabetes Risk Score (FINDRISC) as a screening tool for hepatic steatosis

Introduction. Hepatic steatosis due to non-alcoholic fatty liver disease is associated with obesity, dyslipidemia, insulin resistance, and type 2 diabetes. The Finnish Diabetes Risk Score (FINDRISC) is a prognostic screening tool to detect people at risk for type 2 diabetes without the use of any blood test. The objective of this study was to evaluate whether FINDRISC can also be used to screen for the presence of hepatic steatosis. Patients and methods. Steatosis was determined by ultrasound. The study sample consisted of 821 non-diabetic subjects without previous hepatic disease; 81% were men (mean age 45 +/- 9 years) and 19% women (mean age 41 +/- 10 years). Results. Steatosis was present in 44% of men and 10% of women. The odds ratio for one unit increase in the FINDRISC associated with the risk of steatosis was 1.30 (95% CI 1.25-1.35), similar for men and women. The area under the receiver operating characteristics curve for steatosis was 0.80 (95% CI 0.77-0.83); 0.80 in men (95% CI 0.77-0.83) and 0.83 (95% CI 0.73-0.93) in women. Conclusions. Our data suggest that the FINDRISC could be a useful primary screening tool for the presence of steatosis.

A long-term prospective randomized controlled study of non-specific interstitial pneumonia (NSIP) treatment in scleroderma

The association of cyclophosphamide (CYC) and prednisone (PRED) for the treatment of lung fibrosis in systemic sclerosis (SSc) was only evaluated in uncontrolled studies, although in idiopathic interstitial lung disease (ILD) this association seems to be beneficial in patients with non-specific interstitial pneumonia (NSIP). Objectives: To treat SSc-ILD in a prospective open-label controlled study based on lung pattern during 12 months of treatment. Methods: A 3-year analysis was also performed. Twenty-four consecutive patients with SSc and ILD were submitted to an open lung biopsy. Eighteen patients (NSIP) were randomized in two groups: CYC versus CYC + PRED during 12 months. Lung function tests (diffusion lung capacity of monoxide carbone corrected for hemoglobin concentration (DLCO-Hb), forced vital capacity (FVC), total lung capacity) and Modified Rodnan Skin Score (MRSS) were performed before, after one of treatment and after 3 years from the end of the treatment. Results: Pulmonary function tests were similar in both groups on baseline. After 1 year of treatment, FVC% was comparable between CYC groups (p = 0.72) and in CYC + PRED (p = 0.40). Three years after the end of treatment, FVC% values (p = 0.39 in group CYC and p = 0.61 in CYC + PRED and p = 0.22 in CYC + PRED) and DLCO-Hb (p = 0.54 in CYC and p = 0.28 in CYC + PRED) were similar compared to 1 year of treatment. We observed a reduction of the MRSS in the CYC + PRED group after 1 year of treatment (p = 0.02); although after 3 years, MRSS values remained stable in both groups. Conclusions: CYC was effective to stabilize lung function parameters in NSIP lung pattern of SSc disease for 3 years after the end of a 1-year therapy.

A prognostic score for AIDS-related diffuse large B-cell lymphoma in Brazil

The aim of this study was to evaluate a prognostic score for aids-related lymphoma (ARL). A retrospective study of 104 patients with ARL treated between January 1999 and December 2007 was conducted. Diffuse large B-cell lymphoma (DLBC) was the most observed histological type (79.8%). The median CD4 lymphocyte count at lymphoma diagnosis was 125 cells per microliter. Treatment response could be evaluated in 83 (79.8%) patients, and 38 (45.8%) reached complete remission (CR); overall response rate was 51.8% (95 CI = 38.5-65.1%). After a median follow-up of 48 months, the 4-year overall survival (OS) rate among all patients was 35.8%, with a median survival time of 9.7 months (95% CI = 5.5-13.9 months). The survival risk factors observed in multivariate analysis (previous AIDS and high-intermediate/high international prognostic index (IPI)) were combined to construct a risk score, which divided the whole patient population in three distinct groups as low, intermediate, and high risk. When this score was applied to DLBC patients, a clear distinction in response rates and in OS could be demonstrated. Median disease-free survival (DFS) for patients that achieved CR was not reached, and DFS in 4 years was 83.0%. Our results show that the reduced OS observed could be explained by poor immune status with advanced stage of disease seen in our population of HIV-positive patients. Further studies will be needed to clarify the role of different treatment approaches for ARL in the setting of marked immunosuppression and to identify a group of patients to whom intensive therapy could be performed with a curative intent.

A Palliative Prognostic Score for Terminally Ill Children and Adolescents With Cancer

Background. The loss of a child is considered the hardest moment in a parent`s life. Studies addressing length of survival under pediatric palliative care are rare. The aim of this study was to improve a survival prediction model for children in palliative care, as accurate information positively impacts parent and child preparation for palliative care. Procedure. Sixty-five children referred to a pediatric palliative care team were followed from August 2003 until December 2006. Variables investigated (also included in previous studies) were: diagnosis, home care provider, presence of anemia, and performance status score given by the home care provider. Clinical variables such as symptom number were also used to test the score`s ability to pre-validated using the above variables. The number of symptoms at transition to palliative care does not improve the score`s predictive ability. The sum of the single scores gives an overall score for each patient, dividing the population into three groups by probability of 60-day survival: Group A 80.0%, Group B 38.0%, and Group C 28.5% (P < 0.001). Conclusion. A pediatric palliative care score based on easily accessible variables is statistically significant in multivariate analysis. Factors that increase accuracy of life expectancy prediction enable adequate information to be given to patients and families, contributing to therapeutic decision-making issues. Pediatr Blood Cancer. 2010;55:1167-1171. (C) 2010 Wiley-Liss, Inc.