For a given parameter, TITRIVIN supplies a reference value (V), sometimes called the mean value, together with a confidence interval (e).
The parameter's true value falls within the interval [(V-e); (V+e)] with probability above or equal to 95%.

For the same parameter, each laboratory using the TITRIVIN reference defines uncertainty (u) related to its own results. To be acceptable a measurement should fall within the interval [(V-e)-u; (V+e)+u].

Note: Whatever the laboratory's uncertainty (u) regarding the measurements obtained for the particular parameter, the average of the results over a period, giving a significant number of controls, must fall within the interval [(V-e); (V+e)]. If this does not occur, internal corrective measures must be taken.