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Biomedical subjects

E L Frome

Publications and source records attributed to E L Frome.

29 records · Page 2Linked to original sources
PubMed1983

The analysis of rates using Poisson regression models.

Models are considered in which the underlying rate at which events occur can be represented by a regression function that describes the relation between the predictor variables and the unknown parameters. Estimates of the parameters can be obtained by means of iteratively reweighted least squares (IRLS). When the events of interest follow the Poisson distribution, the IRLS algorithm is equivalent to using the method of scoring to obtain maximum likelihood (ML) estimates. The general Poisson regression models include log-linear, quasilinear and intrinsically nonlinear models. The approach considered enables one to concentrate on describing the relation between the dependent variable and the predictor variables through the regression model. Standard statistical packages that support IRLS can then be used to obtain ML estimates, their asymptotic covariance matrix, and diagnostic measures that can be used to aid the analyst in detecting outlying responses and extreme points in the model space. Applications of these methods to epidemiologic follow-up studies with the data organized into a life-table type of format are discussed. The method is illustrated by using a nonlinear model, derived from the multistage theory of carcinogenesis, to analyze lung cancer death rates among British physicians who were regular cigarette smokers.

Models, Theoretical↗
PubMed1981

Mortality among men employed between 1943 and 1947 at a uranium-processing plant.

Mortality is described in a cohort of 18,869 white males who were employed between 1943 and 1947 at a uranium conversion and enrichment plant in Oak Ridge, Tenn. Workers in certain departments (especially chemical workers) were exposed to high average air levels of uranium dust. Based on deaths reported in 1974 by the Social Security Administration (SSA) and using mortality rates for U.S. white males, standardized mortality ratios (SMRs) for various causes in the entire cohort were generally less than 1.00. After correction for unascertained deaths and missing death certificates, the SMR for lung cancer was 1.22 (95% confidence limits, 1.10 and 1.36). SMRs for various causes, including lung cancer, did not tend to be higher in 8,345 workers employed in areas where uranium dust was present or in 4,008 of these 8,345 workers employed for one year or longer at the plant. Other causes of particular interest (i.e., bone cancer, leukemia, diseases of respiratory and genitourinary systems) did not exhibit high SMRs. The suggestive finding of the authors was an increased number of lung cancer deaths in a group of chemical workers hired at greater than or equal to 45 years of age. Continued follow-up of the cohort is necessary for further evaluation of the long-term health effects of exposure to uranium.

Age Factors↗
PubMed1978

Bioavailability of acetazolamide tablets.

Plasma acetazolamide levels were measured by an enzymatic assay following single 250-mg oral tablet doses to 20 healthy volunteers; five different lots of acetazolamide tablets from a single manufacturer were used in a balanced incomplete block design. From the measured plasma levels, estimates of the bioavailability parameters (area under the plasma concentration versus time curve, time to peak plasma concentration, and peak plasm concentration) were obtained by least-squares digital computer fitting. No significant differences among the tablets were observed (alpha = 0.05) for the analysis of variance of the area under the curve or time to peak parameters. Two tablets, however, provided statistically higher peak plasma concentrations than the other three. Thus, lot-to-lot bioinequivalence of acetazolamide tablets was observed. Some in vitro tests employed showed general trends for correlation with the in vivo data. However, considerable refinement of these technique appears necessary for in vitro prediction of the observed lot-to-lot bioinequivalence.

Acetazolamide↗
PubMed1977

Pharmacokinetics of orally administered hydroflumethiazide in man.

Hydroflumethiazide plasma and urine levels were measured fluorometrically following the oral administration of 100-mg doses (2 X 50 mg tablets) to each of 12 healthy, adult male subjects. The plasma level data as a function of time were fit to a one-compartment open model using a nonlinear regression digital computer program. The means of the individual apparent absorption and disposition rate apparent absorption and disposition rate constants were 0.770+/-0.46 hr(-1) (t1/2=0.9 hr) and 0.358+/-0.17 hr(-1) (t1/2=1.94 hr), respectively, with a 0.49+/-0.26 hr lag time in absorption. The same parameter estimates obtained by fitting the mean plasma concentration-time curve were 0.461+/-0.15 hr(-1), 0.357+/-0.13 hr(-1), and 0.39+/-0.09 hr for the apparent absorption and disposition rate constants and the lag time, respectively. The closeness of the parameter estimates and the lack of intravenous data preclude unequivocal assignment of the rate constants to the absorption or disposition processes. Nevertheless, the disposition of hydroflumethiazide is clearly a rapid process. The means of the individual peak plasma levels and times to peak were 0.301+/-0.94 microgram/ml and 2.12+/-0.59 hours, respectively. The mean area under the plasma level-time curve was 1.95+/-0.78 microgram-hr/ml and 46.7+/-20.0% of the administered dose was recovered in the 24-hour urine. The mean renal clearance of hydroflumethiazide was 453.4+/-256.6 ml/min.

Administration, Oral↗
PubMed1976

Power spectrum of the respiratory system.

Spectrum analysis is proposed as a method for analyzing biologic time series data that arise in the study of respiration. A mechanical model of the respiratory system is used to provide a theoretical basis for the interpretation of the air flow spectrum in terms of a physically defined energy concept. We show that under certain conditions the flow variance is proportional to the mechanical work of breathing, and indicate how this new parameter is related to conventional measures of respiratory function. An example is presented to describe the computational procedure and to illustrate the graphical aspects of cross-spectrum analysis.

Adult↗