The design of an investigation study is the general plan of the investigator to obtain the answer to a raised question, that is to verify the investigation hypothesis. The selection of the type of design depends on the objective of the study, the resources on which count the investigator, the scope where to the results and the ethical requirements will be applied. All clinical test is based on the experimental method. The objective of this type of studies is to so obtain data on way medicines that it is possible to evaluate and to compare his effectiveness and security in one or more groups of individuals. In the studies that are carried out in a group of patients to those who he himself drug is administered to them, can be established criteria to change a medicine by another one or to change the doses (studies of phase I and 11) and of this form to evaluate the differences between different drugs or different doses from a same drug. Generally in the pharmacoclinics studies two or more groups of compare themselves to whom different treatments are administered to them. The simplest design consists of two groups of patients, a group that receives the drug in investigation and another group that receives placebo or the best one of the treatments available for the disease in study. The results of both treatments are compared and the differences settle down. The allocation of the treatments to each one of the groups is made in randomized form, that is at random. This means that the volunteers can be assigned at random to a group of treatment by means of numbers generated by a computer, applying a table of random numbers or, simply, removing the names from a hat. Of this form it is avoided that the subjectivity of the investigator takes part in the process of allocation of the treatments to the patients and allows that each patient counts on the same possibilities of being assigned to one or another group of treatment. Therefore, it can be assumed that the identified factors that can take to confusion are not identical in both groups and that the groups only defer to each other in which concerns the drug in investigation. If the allocation of treatments is not made in randomized form (for example when it is assigned according to the date of birth, number of clinical history of the patient, day from the visit to the doctor's office, availability of bed or another strategy that allows the investigator to know the allocation before obtaining the consent of the patient) can happen a misalignment in the allocation of treatments and take place a slant. Slant to the confusion or involuntary alterations in the results of a study is denominated. The controlled studies include a called group of reference group control. The group control is a group of patients to whom a treatment is administered to him against which they compare so much the effectiveness as the security of the new drug in study. The existence of the group control allows to compare, to establish causality and statistical meaning. The election of the group control is fundamental. Ideally all clinical test must have a group placebo (medication that does not contain any active drug) like control since it allows to the unequivocal demonstration of the effectiveness and security of a medicine. Nevertheless, for ethical reasons, due to the existence of treatments for most of the diseases, not always placebo in the group is used control. - The group control can be:1)Placebo .
2)Active Comparator or medicine pattern, is the best existing treatment until the moment for the disease in study .
3)Historical Control, are registries of answers to devices or obtained drugs before an investigation study begins. The historical control only must be used in exceptional cases, like very rare diseases, that they do not allow reuniting a sufficient number of patients or for the drug study that is used in the treatment of lethal diseases like cancer or AIDS.
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Wednesday, July 25th, 2007 at 6:53 am
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