Modification of the error-rate bounded classification scheme for use with two MIC break points.

Area of Science:

• Clinical Microbiology
• Antimicrobial Resistance
• Diagnostic Test Development

Background:

• Antimicrobial susceptibility testing relies on minimum inhibitory concentration (MIC) and disk diffusion (zone diameter, Z) break points.
• Current methods for establishing Z break points are limited, especially when using two MIC break points to categorize susceptibility (susceptible, intermediate, resistant).

Purpose of the Study:

• To develop a methodology for determining optimal Z break points when two MIC break points are used.
• To provide an efficient search method for identifying these optimal Z break points.

Main Methods:

• The study proposes deriving an index as a function of Z break points.
• A search method is presented to find optimal Z break points based on this index.
• The methodology was evaluated using a specific data set.

Main Results:

• The proposed methodology successfully determines Z break points for tiered susceptibility categories.
• The index-based search method requires examining only a small fraction of possible solutions.
• This approach is more efficient than enumerating all feasible Z break-point pairs.

Conclusions:

• A novel and efficient methodology for determining Z break points in antimicrobial susceptibility testing is established.
• This method facilitates accurate prediction of organism susceptibility and minimizes misclassification errors.
• The approach is particularly valuable for scenarios involving multiple MIC break points.