Rejoinder to Kullback and Keegel note on the minimum discrimination information approach

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25674/1/0000227.pd

The Michigan Model for Coronary Heart Disease in Type 2 Diabetes: Development and Validation

Objectives: The aim of this study was to develop and validate a computer simulation model for coronary heart disease (CHD) in type 2 diabetes mellitus (T2DM) that reflects current medical and surgical treatments. Research Design and Methods: We modified the structure of the CHD submodel in the Michigan Model for Diabetes to allow for revascularization procedures before and after first myocardial infarction, for repeat myocardial infarctions and repeat revascularization procedures, and for congestive heart failure. Transition probabilities that reflect the direct effects of medical and surgical therapies on outcomes were derived from the literature and calibrated to recently published population-based epidemiologic studies and randomized controlled clinical trials. Monte Carlo techniques were used to implement a discrete-state and discrete-time multistate microsimulation model. Performance of the model was assessed using internal and external validation. Simple regression analysis (simulated outcome=b0+b1?published outcome) was used to evaluate the validation results. Results: For the 21 outcomes in the six studies used for internal validation, R2 was 0.99, and the slope of the regression line was 0.98. For the 16 outcomes in the five studies used for external validation, R2 was 0.81, and the slope was 0.84. Conclusions: Our new computer simulation model predicted the progression of CHD in patients with T2DM and will be incorporated into the Michigan Model for Diabetes to assess the cost-effectiveness of alternative strategies to prevent and treat T2DM.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140355/1/dia.2014.0304.pd

Rejoinder

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25673/1/0000226.pd

On maximum likelihood estimation in sparse contingency tables

Log-linear and logistic models can be fitted to data in contingency tables either by an iterative proportional fitting algorithm or by an iteratively reweighted Newton-Raphson algorithm. Both algorithms provide maximum likelihood (ML) estimates of the expected cell frequencies and of the parameters of the model. When random zeros occur in the contingency table, numerical problems may be encountered in obtaining the ML estimates when using one or both of the algorithms. Problems in the estimation of the model's parameters, expected cell frequencies and degrees of freedom are described. An explicit formula is given for the evaluation of the degrees of freedom.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25269/1/0000712.pd

Detection of a random alteration in a multivariate observation when knowing probable direction

An observation from a multivariate distribution may be subject to perturbation in a known subset of the variables. A likelihood radio statistic is developed to test whether or not there has been an addition of a random quantity in a prespecified direction to an observation from a multivariate normal distribution. When the variance of this addition is unknown, a secondarily Bayes approach is used to eliminate this variance which acts as a nuisance parameter. The testing procedure is based on a distribution-free tolerance interval.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27380/1/0000409.pd

Estimation of the variance of percentile estimates

The asymptotic formula for the variance of a percentile estimate is inversely proportional to the square of the probability density function evaluated at that percentile. In this note we show, for small and moderate sample sizes, that the estimate of the variance can have a moderate to large coefficient of variation even when the form of the density is known. When the density must be estimated empirically, the coefficient of variation increases substantially. We conclude that the estimate of the variance should not be used in either confidence interval estimation or hypothesis testing except for very large sample sizes.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25275/1/0000718.pd

The effect of imputed values on the distribution of the goodness-of-fit chi-square statistic

A method used to compensate for nonresponse is to impute missing values; that is, to replace each missing value with a respondent value selected from all observed values or from a subset of observed values. The imputation procedure used in this paper selects imputed values from the respondent data using simple random sampling with replacement within homogeneous subsets and replaces the missing values with these values to complete the data set. The empirical distribution of the goodness-of-fit chi-square statistic computed from the `completed' data set is compared to its asymptotic distribution and to the distribution of the traditional chi-square test statistic applied to the completed data set by ignoring the imputation.At nominal levels of five and ten percent, the asymptotic distribution of the goodness-of-fit chi-square statistic computed from the completed data set is shown to have a good empirical behavior at moderate sample sizes. When the imputed values are treated as actual responses and the imputation is ignored, the empirical levels of significance are much larger than the nominal levels.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26909/1/0000475.pd

Screening for prediabetes and type 2 diabetes in dental offices

ObjectivesMost Americans see dentists at least once a year. Chair‐side screening and referral may improve diagnosis of prediabetes and diabetes. In this study, we developed a multivariate model to screen for dysglycemia (prediabetes and diabetes defined as HbA1c ≥5.7 percent) using information readily available to dentists and assessed the prevalence of dysglycemia in general dental practices.MethodsWe recruited 1,033 adults ≥30 years of age without histories of diabetes from 13 general dental practices. A sample of 181 participants selected on the basis of random capillary glucose levels and periodontal status underwent definitive diagnostic testing with hemoglobin A1c. Logistic models were fit to identify risk factors for dysglycemia, and sample weights were applied to estimate the prevalence of dysglycemia in the population ≥30 years of age.ResultsIndividuals at high risk for dysglycemia could be identified using a questionnaire that assessed sex, history of hypertension, history of dyslipidemia, history of lost teeth, and either self‐reported body mass index ≥35 kg/m2 (severe obesity) or random capillary glucose ≥110 mg/dl. We estimate that 30 percent of patients ≥30 years of age seen in these general dental practices had dysglycemia.ConclusionsThere is a substantial burden of dysglycemia in patients seen in general dental practices. Simple chair‐side screening for dysglycemia that includes or does not include fingerstick random capillary glucose testing can be used to rapidly identify high‐risk patients.Practical implicationsFurther studies are needed to demonstrate the acceptability, feasibility, effectiveness, and cost‐effectiveness of chair‐side screening.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/113762/1/jphd12082.pd

Expression of KOC, S100P, mesothelin and MUC1 in pancreatico-biliary adenocarcinomas: development and utility of a potential diagnostic immunohistochemistry panel

<b>Background</b> Pancreatico-biliary adenocarcinomas (PBA) have a poor prognosis. Diagnosis is usually achieved by imaging and/or endoscopy with confirmatory cytology. Cytological interpretation can be difficult especially in the setting of chronic pancreatitis/cholangitis. Immunohistochemistry (IHC) biomarkers could act as an adjunct to cytology to improve the diagnosis. Thus, we performed a meta-analysis and selected KOC, S100P, mesothelin and MUC1 for further validation in PBA resection specimens.<p></p> <b>Methods</b> Tissue microarrays containing tumour and normal cores in a ratio of 3:2, from 99 surgically resected PBA patients, were used for IHC. IHC was performed on an automated platform using antibodies against KOC, S100P, mesothelin and MUC1. Tissue cores were scored for staining intensity and proportion of tissue stained using a Histoscore method (range, 0–300). Sensitivity and specificity for individual biomarkers, as well as biomarker panels, were determined with different cut-offs for positivity and compared by summary receiver operating characteristic (ROC) curve.<p></p> <b>Results</b> The expression of all four biomarkers was high in PBA versus normal ducts, with a mean Histoscore of 150 vs. 0.4 for KOC, 165 vs. 0.3 for S100P, 115 vs. 0.5 for mesothelin and 200 vs. 14 for MUC1 (p < .0001 for all comparisons). Five cut-offs were carefully chosen for sensitivity/specificity analysis. Four of these cut-offs, namely 5%, 10% or 20% positive cells and Histoscore 20 were identified using ROC curve analysis and the fifth cut-off was moderate-strong staining intensity. Using 20% positive cells as a cut-off achieved higher sensitivity/specificity values: KOC 84%/100%; S100P 83%/100%; mesothelin 88%/92%; and MUC1 89%/63%. Analysis of a panel of KOC, S100P and mesothelin achieved 100% sensitivity and 99% specificity if at least 2 biomarkers were positive for 10% cut-off; and 100% sensitivity and specificity for 20% cut-off.<p></p> <b>Conclusion</b> A biomarker panel of KOC, S100P and mesothelin with at least 2 biomarkers positive was found to be an optimum panel with both 10% and 20% cut-offs in resection specimens from patients with PBA.<p></p&gt

Half-life and spin of 60Mn^g

A value of 0.28 +/- 0.02 s has been deduced for the half-life of the ground state of 60Mn, in sharp contrast to the previously adopted value of 51 +/- 6 s. Access to the low-spin 60Mn ground state was accomplished via beta decay of the 0+ 60Cr parent nuclide. New, low-energy states in 60Mn have been identified from beta-delayed gamma-ray spectroscopy. The new, shorter half-life of 60Mn^g is not suggestive of isospin forbidden beta decay, and new spin and parity assignments of 1+ and 4+ have been adopted for the ground and isomeric beta-decaying states, respectively, of 60Mn.Comment: 13 pages, 5 figures, Accepted for publication in Phys. Rev.