A reference value for each parameter

 This isn’t an average but a value obtained by robust statistical calculation.

The confidence interval

This corresponds to the uncertainty (u) of the reference value with k = 2. This means the “true” value of this parameter is between [Vref – u ; Vref + u].

Two possible uses :

In control :

This is the interval in which the laboratory must find the average of their results (= target of control chart).

In calibration :

This is the interval in which the laboratory can give a value when it use TITRIVIN as a standard. The  calibration must be assessed with this value.
In most situations, you can give the reference value as the standard value. But you can use a value in the confidence interval , if it’s necessary to obtain a best calibration curve.

The acceptance interval

This corresponds to the maximal value that a laboratory can accept for the reference value when it analyses TITRIVIN the first time.

This interval is useful when you use TITRIVIN for the first time at the beginning of your quality control. You can have an idea of your performance when you build a control chart. Your results have to be in the acceptance interval.

 Otherwise, it can mean an accuracy problem.

When your quality control is in place, you must use the confidence interval.