Microbiological proficiency testing: Establishing a fixed standard deviation for proficiency assessment

The evaluation of use a specific fixed standard deviation for the proficiency assessment (σ pt ) in three Chilean microbiological proficiency testing scheme was discussed in this study. The σ pt proposed in the standards (0.25 and 0.35) was not appropriate for these microbiological schemes. Nevertheless, a better fixed σ pt value was established for that purpose, considering the characteristic of the round in terms of the matrix, included microorganisms (concentration and strain), and target group of participation.