It is important to note that evaluation groups are formed from the most specific, such as “Kit/Equipment,” to the most generic or less specific, such as “All Vitros kits,” for example.

Based on statistical studies, groups are organized according to the affinity of analytical systems (systems with similar behavior). These studies are conducted in accordance with ISO 13528 and assess the feasibility of evaluating systems that would not be analyzed in specific groups. This process is carried out with great care to ensure that such groups are evaluated safely and with appropriate data.

It is also worth mentioning that internal control (IC) and proficiency testing (PT) serve different purposes. While IC assesses the reproducibility of results, in PT it is essential to consider the target value of the samples (usually represented by the group mean). It is important to verify whether the reagent batch being used is suitable, taking into account that it is a secondary batch, as some kits may exhibit significant differences between batches.

The standard uncertainty (u) data for the evaluation group (EG) is made available in the results profile. According to ISO 13528 (2022), this uncertainty can be calculated using the formula u = 1.25*SD/√(Quantity) or obtained through the bootstrap method (a resampling technique). This uncertainty reflects the dispersion of values associated with the mean of the evaluation group (EG), but it does not replace the laboratory’s uncertainty and should not be considered in its calculation.

The laboratory’s uncertainty must be obtained and interpreted within the context of its routine activities.