A restriction of our tool is the requirement that the population -the donors- be constant over the time. Therefore, biological samples can be drawn from the same subject over time, so that the evolution of any parameter and the influence of the temporary variable on it can be studied, and so that the influence of any other characteristic on the study variable can be analysed.

In the case of constant population, one of the most commonly used methods by researchers for data analysis is so-called Longitudinal Analysis, usually developed with statistical techniques.

Longitudinal Analysis can be defined as the detailed examination of the data and the evidence showing trends over time.

Longitudinal data means a set of data collected over time on a population that remains constant.