Clinical trials are the most commonly used types of clinical epidemiological studies. They are patient-based studies that are often used to evaluate the effectiveness of a drug or treatment. Mainly include:
1. treatment research
It includes the evaluation of the efficacy or adverse reactions of drugs, therapies, medical devices and other medical and health services.
2. diagnostic studies
To evaluate the authenticity, reliability and clinical value of a diagnostic test.
3. screening studies
To evaluate the validity, reliability and practicability of a screening method for a disease in a large population.
4. prognostic study
It is mainly used for the study of prognostic factors.
5. etiology study
Clinical trials are used for the study of etiology, mainly for intervention of disease risk factors.
Basic elements
The basic elements of clinical trials include: processing factors, subjects and experimental effects.
(1) processing factors
Processing factors refer to the factors that the researcher imposes on the experimental unit according to the purpose of the study and need to be observed and clarified in the experiment. For example, in order to evaluate the efficacy of a new drug, the treatment factor is the drug. We should pay attention to the following two points in studying the treatment factors.
1. clear handling factors and non processing factors.
In a test, too many factors should not be dealt with. Otherwise, the grouping and the number of units needed will increase, and the whole test is difficult to control. While determining the treatment factors, we also need to control the non-treatment factors. Although the non-treatment factors are not the factors studied in this study, they will affect the clinical trial results and produce confounding effects.
2. Standardization of treatment factors
Treatment factors should remain unchanged throughout the test, including the application method, strength, frequency and duration of treatment factors.
(two) subjects
The overall study should be determined according to the purpose of clinical trials. The choice of subjects should be considered in terms of overall representativeness, ethical requirements and patient safety. The inclusion and exclusion criteria should be relaxed as much as possible while maintaining the homogeneity of the subjects in order to accurately estimate the processing effects. In order to enable subjects to represent the research population, multicenter clinical trials are often adopted.
(three) test effect
The test effect refers to the various effects produced by the processing factors on the subjects. We should select indicators that can objectively and comprehensively reflect the test effect. If there are multiple main indicators in the study, I errors should be adjusted in statistical analysis.
Basic principle
1. random
Distribution of samples into which each observer has a completely equal chance of being drawn or assigned to a group, independent of the subjective wishes of the researcher or the subject. The aim is to achieve “inter group balance”.
2. control
Sometimes the clinical observation of the experimental effect is not necessarily the role of treatment factors, often there is the role of non-treatment factors. In order to distinguish the effects caused by non treatment factors, we need to set up a control group.
3. repetition
It means that there should be a certain number of repeated measurements between the experimental group and the control group, that is, if the experimental unit wants to reach a certain reasonable sample size, the research conclusion can be extrapolated to other patients with the same nature as the research object.
4. objective
Blind method is adopted to avoid the influence of subjective factors of researchers and researchers on research effect.
5. multi center
Multicenter clinical trials can collect a large number of subjects in a relatively short time, avoiding the limitations that a single research institution may have.
6. ethics
This is the premise of all clinical trials.
Basic design type
1. parallel design
The subjects were randomly assigned to two groups (or more groups) to receive different treatments, and the two groups began the study at the same time, and the results were analyzed and compared. The most widely used type of experimental design.
2. cross design
The two groups of subjects were treated with two different treatment measures, then the treatment measures were exchanged with each other, and finally the results were compared and analyzed. The efficiency of the method is higher than that of parallel design, and the sample size is small. But it is only suitable for recurrent chronic diseases.
3. factorial design
It means that treatment factors cross to form different treatment groups and evaluate them simultaneously, so as to evaluate the interaction of individual and combined effects of different treatments. It applies to the analysis of interaction factors among multiple processing factors.
4. sequential design
Sequential design does not specify the sample size before the trial. Patients are randomized into the trial group and the control group according to the order of entry. After each test or a pair of subjects are analyzed in time, the test can be stopped once the results can be determined. It is suitable for experiments based on single index and quick results.
