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At least 19 recordsLinked to original sources
PubMed1977

A method for the determination of confidence limits for the P/2e- ratio for chosen values of ymaxatp form the results of continuous culture experiments.

A model is described, which allows the determination of 95% confidence limits for the maintenance coefficient and the efficiency of oxidative phosphorylation for chosen values of the growth yield for ATP corrected for energy maintenace (YmaxATP). As experimental data the specific rates of substrate consumption, product formation and oxygen uptake in chemostat cultures at various growth rates are use.

Bacteria↗
PubMed1992

Confidence limit analyses should replace power calculations in the interpretation of epidemiologic studies.

Frequently, after an epidemiologic study is completed, statistical power to detect a relative risk of interest is recalculated using data obtained during the course of the study. A negative study may then be dismissed on the grounds that its power was too low. However, post hoc power calculations ignore the actual relative estimate and its variance, which are by then known. We present evidence that post-study power calculations have little value and should be replaced by a more informative method using the upper (1 - alpha)% confidence limit of the point estimate that touches the value of the relative risk of interest.

Confidence Intervals↗
PubMed1977

Exclusion of chromosomal mosaicism: tables of 90%, 95% and 99% confidence limits and comments on use.

Tables specifically tailored to the exclusion of cytogenetic mosaicism at three confidence levels are presented. The consequences of the assumption of independence in application of the binomial theorem to this question are discussed. The tables are most applicable to the number of cells evaluated from cultures in which all mitoses are arrested in the first in vitro division. For long-term cultures the tables are conservatively applicable to the number of separate colonies evaluated. If n cells have been evaluated from phytohemagglutinin stimulated peripheral blood after 72 hr in cultures, the tables are applicable to between n/2 and n cells.

Chromosomes↗
PubMed1978

An iterative approach to the analysis of EM autoradiographs. II. Estimates of sample sizes and confidence limits.

The errors inherent in EM autoradiography are discussed and certain of them deemed to be of particular practical significance in the quantitative assessment of preparations. A method is described for estimating the standard errors attributable to each of several sources of variation and thence for obtaining the overall standard error value to be attached to relative activity estimates obtained in the method of Downs & Williams (1978). In an appendix, a fully worked example is given illustrating clearly the strategy of the method and the magnitudes of error estimates that are to be attached to the final specific activity values.

Autoradiography↗
PubMed1976

Study of a proposed international standard for blood coagulation factor IX.

An International Collaborative Study was organized to establish a standard for factor IX. Two freeze-dried concentrate preparations, C1 and C2, and one freeze-dried plasma P were compared with each other, with fresh normal plasmas and with local standards in 13 laboratories. One of the concentrate preparations (C1) contained heparin and this gave rise to non-parallel assays in laboratories testing concentrate C1 in dilutions containing more than 0.05 i.u. of heparin per ml. Assays of factor IX showed good precision for both plasma and concentrate in all laboratories; no systematic effect of method, operator or day of assay was detected. The plasma preparation P and the concentrate preparation C2 were compared with 59 individual fresh normal plasma samples, and a mean potency ratio of 0.78 (95% confidence limits 0.73-0.84) for plasma and 5.62(95% confidence limits 5.13-6.16) for the concentrate C2 obtained. Only 21 estimates of concentrate C1 in terms of fresh plasma were obtained giving a mean potency ratio of 3.85 (95% confidence limits 1.87-7.92). The estimated loss of potency for freeze-dried plasma stored at -20 degrees C is approximately 0.4% per year. The concentrate C2 is apparently more stable and only very small losses occurred even at higher storage temperatures. All participants agreed that the preparation C2 would be suitable to serve as an International Standard for factor IX; they also agreed that the figure assigned for the unitage should be based on the number of ml of 'average fresh normal plasma' estimated to contain the factor IX activity of one ampoule of the preparation. It is proposed to recommend to the World Health Organization that the preparation of factor IX concentrate C2, in ampoules coded 72/32, be considered for establishment as the International Standard for factor IX, and that the international unit for factor IX be assigned on the basis of 5.62 units per ampoule of this preparation.

Blood Preservation↗
PubMed1992

A comparison of expiration dating period estimation methods.

Two methods of estimating expiration date have been compared. For a drug whose potency is expected to decrease with time, method 1 fits a linear regression line to the stability data, calculates a 95% lower confidence limit of the true degradation line, and estimates the expiration date by comparing the confidence limit with the lower specification limit. Method 2 calculates a 95% lower confidence limit b1 of the slope of the true degradation line, constructs a new line y" using b1 as its slope, and finally estimates the expiration date by comparing y" with the lower specification limit. In this work we show that in most practical situations, method 1 estimates greater expiration date than method 2.

Chemistry, Pharmaceutical↗
PubMed1979

Repair of tetralogy of Fallot after Waterston anastomosis.

Sixty-three corrective operations have been performed in patients with Tetralogy of Fallot and a previously constructed Waterston shunt. The patients were from 1.4 to 8 years of age (median 4.3 years), and the mean interval between the Waterston shunt and the repair was 39.3 +/- 16.05 months. Three patients developed pulmonary atresia and six required a second anastomosis prior to intracardiac repair. Kinking and stenosis of the right pulmonary artery at the site of the Waterston anastomosis occurred in 12 (19 percent; 70 percent confidence limits 14 to 26 percent) patients who required patch enlargement of the right pulmonary artery at repair. Seven (11 percent; 70 percent confidence limits 7 to 17 percent) patients died in the hospital and three (5 percent; 70 percent confidence limits 2 to 11 percent) during the period of late follow-up. None of the early or late deaths was specifically related to the presence of the previously performed Waterston anastomosis.

Age Factors↗
PubMed1975

Plasma deoxyribonucleic acid concentrations of women in labor and umbilical cords.

The concentration of deoxyribonucleic acid (DNA) in plasma from 30 women in labor and plasma from the umbilical cords was determined with a rapid, inexpensive, and simple fluorometric method. These concentrations of DNA were compared to the plasma DNA concentrations of nonpregnant women. The mean plasma DNA concentration of women in labor was significantly lower than the mean plasma DNA concentration of nonpregnant women in the use of 99 per cent confidence limits. The mean plasma DNA concentration of umbilical cords during the third stage of labor was significantly lower than the mean plasma DNA concentrations of women in labor with the use of 99 per cent confidence limits and of nonpregnant women using 99.9 per cent confidence limits.

Blood Specimen Collection↗
PubMed1992

Lack of interaction between propofol and vecuronium.

We estimated the potency of vecuronium and measured the onset and duration of its action during total intravenous anesthesia with propofol to examine the possibility of any interaction between these two drugs. Propofol infusion was administered according to a three-step dosage scheme, and neuromuscular block was monitored by measuring the force of contraction of the adductor pollicis muscle after single-twitch stimulation of the ulnar nerve at 0.1 Hz. A control group of patients were similarly studied during anesthesia with thiopental, nitrous oxide, oxygen, and fentanyl. The ED50 and ED95 (dose required to produce a 50% and 95% depression of twitch tension, respectively) of vecuronium in patients given total intravenous anesthesia (n = 24) were 24 (22-27, 95% confidence limits) and 41 (37-48, 95% confidence limits) micrograms/kg, respectively, and in the control group (n = 24), 20 (17-24) and 39 (34-37) micrograms/kg, respectively. The onset of action of an 80-micrograms/kg dose (2 x ED95) of vecuronium was 3.6 +/- 1.2 and 4.1 +/- 1.7 min (mean +/- SD), in the propofol (n = 10) and control (n = 10) groups, respectively. The respective times to recovery of the twitch height to 25% of control and the recovery indices (25%-75% recovery of twitch height) in the propofol versus control groups were 28.3 +/- 6.6 and 28.0 +/- 1.7 min and 13.3 +/- 6.8 and 15.4 +/- 11.9 min, respectively. There were no significant differences in any of the measured variables between the propofol and control groups, indicating the lack of any interaction between propofol and vecuronium.

Adult↗
PubMed1977

Correlates of maximal oxygen consumption during treadmill exercise.

According to the Balke treadmill protocol, 39 healthy male USAF volunteers were subjected to maximal exercise. The subjects as a group passed the anaerobic threshold by the end of exercise since average venous lactate concentrations increased from 11.2 +/- 1.6 mg% (95% confidence limits) to 93.0 +/- 8.5 mg% (95% confidence limits), and the average gas exchange ratio (R) at the end of the exercise was greater than unity (p less than 0.0005). Tests for correlations showed weak but statistically significant (p less than 0.05) relationships between change in venous lactic acid concentrations and R (r = 0.44) and maximal heart rate (r = 0.34). Maximal oxygen consumption was correlated with time of exercise (r = 0.70) and subject weight (r = 0.33). Subject age and initial plasma lactate concentrations were not significantly correlated with any other variables. Multiple linear regression yielded an equation for prediction of maximal oxygen consumption which included terms for time of exercise and subject weight. Although the multiple correlation coefficent (r = 0.75) was statistically significant (p less than 0.05), it was considered insufficient for accurate prediction of maximal oxygen consumption.

Adult↗
PubMed1975

Normal hemoglobin-oxygen affinity.

Hemoglobin-xoygen affinity is known to vary in a number of disease states. The authors measured the continuous affinity of blood from healthy subjects and, using mathematical data reduction techniques, calculated coefficients for rational function models of average normal affinity, plus or minus 2 standard deviations, and 95 per cent confidence limits. Average normal P50 was 27.10 torr, with a two-standard-deviation range of 25.85 to 28.35; P50s of the 95 per cent confidence limits were 26.69 and 27.53 torr. The affinity usually accepted as standard lay between or very near to the 95% confidence limits of normal throughout its range. It is concluded that the range of normal affinity is narrow and that, for most practical purposes, standard affinity adequately represents normal affinity. There should be little difficulty in distinguishing from normal the shifts that occur in certain disease conditions.

Acid-Base Equilibrium↗