Methodology:
In this section, I will describe in detailed :
l) The variables that will be evaluated in each clinical study and the form to measure them.
2) The design of the study .
3) Techniques and procedures that are going away to use to reach the proposed objectives.
4) The procedures to safeguard the security of the patients during the study and when finalizing his participation.
1) The variables:
In a clinical study the characteristic to study is named variable.
For example, when the effects of a drug study on the arterial pressure, the values of arterial pressure are the variable in study. We can say that the variables are properties that are not equal in all the individuals but that, like the name say, vary from an individual to another one.
It is sufficient that between different individuals from a population, a property can admit 2 possibilities (values) different so that at least it is considered variable. For example, if the population of the study is “men and women with slight arterial hypertension not treated” the property sex, it is a variable because it can at least adopt 2 different values.
But if the population of the study is “women with slight arterial hypertension treated” the property sex does transform itself into constant because there is no more two different properties and it stops being a variable.
When the variable describes the intervention made by the investigator and the cause of a certain action is considered denominates independent variable. The variable that it describes the result produced by the intervention it denominates dependent.
For example, we suppose that we want to study the factors of risk of anti-inflammatory the secondary digestive hemorrhage to the nonsteroid administration. In this example the investigator administers anti-inflammatory to the patients. The consumption of anti-inflammatory (dose, time of administration) is the independent variable. The appearance of digestive hemorrhage (if it appears) is the dependent variable of the received medication. The variables can be classified in:
,/Variable in study: those on which information in the study looks for and can be deduced of the specific objectives. For example the digestive hemorrhage in the previous example.
,/Variable irrelevant: those that do not have relation with the problem in study. For example the color of eyes of the individuals that participate in 16 clinical study of the previous example .
/Variable to control: those that without being the variables in study, have relation with the created problem and can modify the results of the investigation. For example, in the mentioned study, above the patients who take medicines that also act on the gastric mucosa or protecting it or damaging it .
Once defined the variables in study he must determine itself that measurement scales will be used to measure them, that is that assigns a value to them. The possible values can be numbers or names. The variables are denominated quantitative when they are moderate with representative fractions because the values are numbers that maintain an order and a magnitude and mathematical operations like adding can be made with them, reducing, to multiply or to divide As examples of numerical variables we can mention the values of arterial pressure or the values of hemoglobin.
The variables are called ordinal when the possible values follow a sequence that goes of greater to minor (or vice versa). The ordinal variables can be names (hipoglucemia slight, moderate or severe) or numbers (degree IV of Cardiac Insufficiency determined by the NYHA). The qualitative variables are those that are moderate with nominal or categorical scales because the values are names for example sex or race. The measurement scale that will be used for a variable determines the person who designs the protocol and depends on the precision whereupon she is needed to measure variable happiness based on the design of the study and the availability of the suitable instrument. For example, an investigator can decide to measure the variable glucemia in mg/I, being a this quantitative variable. But, if for the study that carries out, as much detail is not necessary and wants to only register if the individuals are hiperglucémicos severe or no, changes the measurement scale to noun and the variable will be qualitative. It is important to consider that if a variable can be measured in a quantitative scale must become this way, since when choosing a nominal scale loses information.