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Population characteristics of biological systems influenced by multicomponent random and uniform variation.

The total variability associated with the pharmacokinetic disposition of seven therapeutic agents was decomposed into its source components. After differentiating and isolating random components from fixed uniform components of variance, the proportional contribution of random intersubject and intrasubject variance was evaluated. Statistical analysis utilized a mixed-effects probabilistic model which incorporated both random effects and fixed day-to-day effects. In some cases, time-within-day diurnal effects were also incorporated. While significant intersubject effects were found for all seven drugs studied, three of them were characterized by predominant intrasubject variance. Since intrasubject variance represents a measure of the stability of drug disposition, characterization of its relative magnitude is fundamentally important in assessing the therapeutic consequences of a given treatment at any given time. Significant diurnal effects were found which were strikingly invariant.

Adult↗

[Prognosis and risk evaluation of postoperative coronary patients (PERISCOP). Methodology and study population characteristics].

The aim of the PERISCOP study was to evaluate the predictive value of cardiological investigations performed after recent coronary bypass surgery with regards to cardiac event and mortality at one year. The treatment of lipid abnormalities was also analysed. This first article describes the methodology and patient characteristics at inclusion. This prospective national multicenter trial included 2065 patients (86% men) with an average age of 63.1 +/- 9.9 years. The number of diseased vessels was 2.6 +/- 0.6. Preoperative left ventricular function was normal (ejection fraction 60 +/- 13%). Revascularisation was complete in 73% of cases (22% of arterial grafts). The cardiological investigations were performed at Day 20 +/- 10 after surgery. The duration of exercise on stress testing was 429 +/- 170 seconds. It was positive or doubtful in 9% of cases. Ventricular arrhythmias were observed in 6.5% of cases. The blood pressure response was abnormal in 6% of cases. Holter monitoring showed a median number of ventricular extrasystoles over 24 hours of 44. Three per cent of patients had one episode of ventricular tachycardia and 7% had ischaemic episodes. The echocardiographic index of segmental contractility was on average 1.75 (ejection fraction: 52.6%). The lipid analysis performed at one month, under lipid therapy in 34% of cases, showed a total cholesterol level at 1.91 +/- 0.10 g/l, an LDL-cholesterol of 1.27 +/- 0.08 g/l. The therapeutic target (LDL-cholesterol < 1 g/l) was attained in 46% of cases with treatment and in 18% of cases without treatment.

Aged↗

Population characteristics according to recruitment source.

Considerable variability was observed among recruitment sources and centers in the proportion of first protocol visits proceeding to entry. Some of the reasons for these differences are explored. Several characteristics of the participants were also analyzed to determine whether significant variability existed among recruitment sources. The variability encountered suggests that these characteristics might be exploited in selecting recruitment sources for clinical trials.

Adult↗