Reproducibility and indices of discriminatory power of microbial typing methods.

When microbial strain-typing methods are compared, the most important characteristics are typeability, reproducibility, and discriminatory power. While typeability and reproducibility can be presented as numerical values, indices of discriminatory power have only recently been described. This paper examines the relationship between reproducibility and indices of discriminatory power. In an individual typing method, an inverse relationship between reproducibility and discriminatory power appears as the number of test differences required in order to distinguish between strains is increased. A method of standardizing the discriminatory power of a typing method to a predetermined reproducibility is presented. In this way the discriminatory powers of different typing methods can be compared while being standardized for the effect of reproducibility.