Search PubMed⌕ Search

Biomedical subjects

V Hasselblad

Publications and source records attributed to V Hasselblad.

72 records · Page 4Linked to original sources
PubMed1981

Indoor environmental determinants of lung function in children.

Using pulmonary function and family respiratory questionnaire data for 16,689 white children 6 to 13 yr of age from 7 geographic areas, the investigators examined the effect of several environmental and other factors on performance, in a standard test of breathing. As expected, FEV0.75 was correlated most strongly with age, height, and sex. A dose-response relationship was observed with maternal smoking habits and explained 0.1% of the variance. No effect caused by the father's smoking habits was observed. A decrease (p = 0.0524) in FEV among older girls was associated with the presence of a gas cooking stove in the home. Although the statistical significance of the decreases was largely attributable to the size of the sample, the decreases in FEV, even though small, were thought to be biologically significant.

Adolescent↗
PubMed1978

Spirometric changes in normal children with upper respiratory infections.

Recent evidence that certain uncomplicated upper respiratory infections induce pulmonary function abnormalities in adults prompted a prospective study in children, in whom such infections occur more frequently. In a longitudinal study, 55 children 2.5 to 11 years of age were observed for a mean duration of 2 years. Spirometry and lung volume studies were obtained routinely every 3 months, during each upper respiratory infection, and 4 weeks after illnes, providing data for 617 "well" and 237 "illness" observations. After grouping of data by sex and age (less than 84 of greater than 84 months), each spirometric parameter was analyzed using linear regression with individual identification, height, and clinical status (normal versus upper respiratory illness) as independent variables. Adjusted mean values of forced vital capacity, 1-sec forced expiratory volume, peak expiratory flow, maximal mid-expiratory flow, and expiratory flow at 50 per cent of the forced vital capacity all decreased during upper respiratory illness. The data suggest that lower respiratory tract involvement without signs or symptoms of lower airway or alveolar disease occurs with upper respiratory illnesses of varied etiologic origin in childhood.

Body Height↗
PubMedDate not supplied

Diagnostic efficiency of home pregnancy test kits. A meta-analysis.

OBJECTIVE: To assess the diagnostic efficiency of home pregnancy test (HPT) kits. DATA SOURCES: A literature search of English-language studies was performed with MEDLINE and a review of bibliographies. STUDY SELECTION: Studies were included if HPT kits were compared with a criterion standard (laboratory testing), if they used appropriate controls, and if data were available to determine sensitivity and specificity. DATA EXTRACTION: Two investigators independently extracted data, and disagreement was resolved by consensus. Sensitivity, specificity, and an effectiveness score (a measure of the discriminatory power of the test, with higher scores implying greater effectiveness) were calculated. DATA SYNTHESIS: Five studies evaluating 16 HPT kits met the inclusion criteria. The range of sensitivities for HPT kits was 0.52 to 1.0. In studies where urine samples obtained by the investigators were tested by volunteers, sensitivity was 0.91 (95% confidence interval [CI], 0.84-0.96). However, the sensitivity was less in studies where subjects were actual patients who performed the test on their own urine samples (sensitivity, 0.75 [95% CI, 0.64-0.85]). The test effectiveness score was 2.75 (95% CI, 2.3-3.2) for studies where subjects were volunteers but deteriorated to 0.82 (95% CI, 0.4-1.2) for studies with actual patients. CONCLUSIONS: The diagnostic efficiency of HPT kits is greatly affected by characteristics of the users. Despite the popularity of these kits, the relatively low effectiveness scores of these kits when used by actual patients are of concern. We suggest that manufacturers of HPT kits publish results of trials in actual patients before marketing them to the general public.

Female↗
PubMedDate not supplied

Clinical outcomes of therapeutic agents that block the platelet glycoprotein IIb/IIIa integrin in ischemic heart disease.

BACKGROUND: Several platelet glycoprotein (GP) IIb/IIIa receptor antagonists have been evaluated in clinical trials. We conducted a systematic overview (meta-analysis) to assess the effect of these compounds on death, myocardial infarction (MI), and revascularization. METHODS AND RESULTS: ORs were calculated for 16 randomized, controlled trials of GP IIb/IIIa inhibitors. An empirical Bayesian random-effects model combined the outcomes of 32 135 patients. There was a significant mortality reduction by GP IIb/IIIa inhibitors at 48 to 96 hours, with an OR of 0.70 (95% CI, 0. 51 to 0.96; P<0.03), equivalent to a reduction of 1 death per 1000 patients treated. Mortality benefits at 30 days (OR, 0.87; 95% CI, 0. 74 to 1.02; P=0.08) and 6 months (OR, 0.97; 95% CI, 0.86 to 1.10; P=0.67) were not statistically significant. For the combined end point of death or MI, there was a highly significant (P<0.001) benefit for GP IIb/IIIa inhibitors at each time point. The 30-day OR was 0.76 (95% CI, 0.66 to 0.87), or 20 fewer events per 1000 patients treated. For the composite end point of death, MI, or revascularization, there was also a highly significant (P<0.001) benefit for GP IIb/IIIa inhibitors. At 30 days, the OR was 0.77 (95% CI, 0.68 to 0.86), or 30 fewer events per 1000 patients treated. The risk differences for death, death or MI, and composite outcomes were similar at 6 months, indicating a sustained absolute improvement. Similar benefit was seen when trials were subgrouped by therapeutic indication (percutaneous intervention versus acute coronary syndromes). CONCLUSIONS: Application of this new therapeutic class to clinical practice promises substantial benefit for both indications.

Double-Blind Method↗
PubMedDate not supplied

An introduction to a Bayesian method for meta-analysis: The confidence profile method.

The Confidence Profile Method is a new Bayesian method that can be used to assess technologies where the available evidence involves a variety of experimental designs, types of outcomes, and effect measures; a variety of biases; combinations of biases and nested bases; uncertainty about biases; an underlying variability in the parameter of interest; indirect evidence; and technology families. The result of an analysis with the Confidence Profile Method is a posterior distribution for the parameter of interest, posterior distributions for other parameters, and a covariance matrix for all the parameters in the model. The posterior distributions incorporate all the uncertainty the assessor chooses to describe about any of the parameters used in the analysis.

Bayes Theorem↗
PubMedDate not supplied

Meta-analytic tools for medical decision making: a practical guide.

This paper is an extension of notes used for the short course in meta-analysis given at the 13th and 14th annual meetings of the Society for Medical Decision Making. The material covers both standard and evolving methods of meta-analysis. The methods include those for combining p-values, for analyzing general fixed-effects models, for analyzing contingency tables, and for analyzing count and continuous outcomes. For each general method, the authors present simplified formulas first, followed by more precise formulas when necessary. Similarly, both classic and Bayesian methods are presented where appropriate. Actual examples are used for methods.

Child↗
PubMedDate not supplied

Assessing uncertainty in cost-effectiveness analyses: application to a complex decision model.

A framework for quantifying uncertainty about costs, effectiveness measures, and marginal cost-effectiveness ratios in complex decision models is presented. This type of application requires special techniques because of the multiple sources of information and the model-based combination of data. The authors discuss two alternative approaches, one based on Bayesian inference and the other on resampling. While computationally intensive, these are flexible in handling complex distributional assumptions and a variety of outcome measures of interest. These concepts are illustrated using a simplified model. Then the extension to a complex decision model using the stroke-prevention policy model is described.

Bayes Theorem↗
PubMedDate not supplied

Meta-analysis of multitreatment studies.

Studies comparing more than two competing therapies are common in several fields, but standard meta-analytic methods can make only pairwise comparisons. The methods proposed in this article, a generalization of current meta-analytic methods, allow for any number of competing therapies and include both fixed- and random-effects models.

Adrenergic beta-Agonists↗
PubMedDate not supplied

Predicting the cost of illness: a comparison of alternative models applied to stroke.

Predictions of cost over well-defined time horizons are frequently required in the analysis of clinical trials and social experiments, for decision models investigating the cost-effectiveness of interventions, and for macro-level estimates of the resource impact of disease. With rare exceptions, cost predictions used in such applications continue to take the form of deterministic point estimates. However, the growing availability of large administrative and clinical data sets offers new opportunities for a more general approach to disease cost forecasting: the estimation of multivariable cost functions that yield predictions at the individual level, conditional on intervention(s), patient characteristics, and other factors. This raises the fundamental question of how to choose the "best" cost model for a given application. The central purpose of this paper is to demonstrate how to evaluate competing models on the basis of predictive validity. This concept is operationalized according to three alternative criteria: 1) root mean square error (RMSE), for evaluating predicted mean cost; 2) mean absolute error (MAE), for evaluating predicted median cost; and 3) a logarithmic scoring rule (log score), an information-theoretic index for evaluating the entire predictive distribution of cost. To illustrate these concepts, the authors conducted a split-sample analysis of data from a national sample of Medicare-covered patients hospitalized for ischemic stroke in 1991 and followed to the end of 1993. Using test and training samples of about 500,000 observations each, they investigated five models: single-equation linear models, with and without log transform of cost; two-part (mixture) models, with and without log transform, to directly address the problem of zero-cost observations; and a Cox proportional-hazards model stratified by time interval. For deriving the predictive distribution of cost, the log transformed two-part and proportional-hazards models are superior. For deriving the predicted mean or median cost, these two models and the commonly used log-transformed linear model all perform about the same. The untransformed models are dominated in every instance. The approaches to model selection illustrated here can be applied across a wide range of settings.

Cerebrovascular Disorders↗