[Use of « Reference change value » in medical biology: about two examples: total PSA and hemoglobin].

The interpretation of the variation between the results of two dosages performed on the same patient is generally quite empirical. It is usually based on the experience of the biologist or physician. Through two examples, total PSA and hemoglobin, we hoped to set up an indicator of the significance variation between results: The Reference change value or RCV to provide assistance to the validator biologist and prescriber based on measured statistical arguments. This article describes the methodology used for the RCV calculation, the formatting on analysis reports and the limitations of the system.