Relevance of correlation between treatment responses in clinical trials.

Background: We recently demonstrated that in self-controlled clinical trials using t-statistic the correlation level between treatment responses is an important determinant of the sensitivity of testing.

Methods: The current study uses hypothetical examples and real data to study whether this phenomenon also affects other parametric statistical procedures.

Results: With negative correlations between treatment responses, not only paired t-test, but also repeated measures analysis of variance (ANOVA), Bonferroni adjustments for ANOVA, and therapeutic equivalence testing, lack sensitivity to demonstrate significant results.

Present status of HMG reductase inhibitors in treatment of dyslipidemia.

HMG reductase inhibitors have significant desirable effects on patients with dyslipidemia. Multiple factors are involved in these desirable effects. Other factors that might play a role in the risk of coronary artery disease are fibrinogen concentration, homocysteine, Lp (a), small dense LDL, insulin resistance, and infection with chlamydia.

Low molecular weight heparins better than unfractionated heparin in unstable coronary artery disease? Unstable angina pectoris/non-Q wave infarction a partly outpatient clinic condition?

Important theoretical advantages of low molecular weight heparins compared to standard heparin include better inactivation of the coagulation mechanism as well as better bioavailability and pharmacokinetic properties. In patients with unstable angina pectoris/non-Q wave infarction these advantages may translate into a reduced combined risk of death, myocardial infarction, and recurrent angina as well as a reduced risk of bleeding, although data so far are limited. Data on quality of life, cost analysis, and patient compliance are missing.

Clinical trials: specific problems associated with the use of a placebo control group.

The topic of placebos in clinical research has been recently addressed in general medical journals, and is relevant to a clinical pharmacologists' readership as well. In this article we try to give an overview of the benefits as well as problems of this methodology. Although the use of placebos in drug development is frequently absolutely essential, important ethical and technical problems are generally involved.