Wrong Sigma metric causes chaos

Abstract

I read the recently published paper by Ozdemir et al. [1] with great interest. In the paper, the authors pointed out an important issue related to the harmonization of Sigma metric (SM) as the performance criteria in laboratory medicine. I agree with the authors that harmonization is needed for SM in laboratory medicine. However, accurate calculation of SM is essential prior to harmonization. As detailed below, SM cannot be accurately calculated using the methodology and equation given in the paper [1] and consequently harmonization of SM cannot be achieved as proposed by the authors. As stated by Albert Einstein ‘everything should be made as simple as possible, but not simpler’. The original equation used to calculate SM is very simple and based on the normal distribution [2].