Introduction: The aim of the this study was to assess the biological variation and reference change value (RCV) for creatinine in healthy individuals aged 18 - 45 years using both Jaffe and enzymatic methods.
Methods: Blood samples were collected from ten females and ten males, for four consecutive weeks in our labora-tory between November and December 2018. Samples were stored at -80°C before analysis and dissolved in one run and analyzed in duplicate in a single study with the Beckman Coulter AU2700 biochemistry analyzer. Data was evaluated using CV-ANOVA, and analytical (CVA), intra-individual (CVI), and inter-individual (CVG) variations were calculated. The RCV was calculated using the formula.
Results: The average CVA calculated at 95% confidence interval for creatinine using Jaffe's method was 2.51%, CVI was 4.51%, and CVG was 14.17%. The same measures for creatinine were 2.43%, 4.21% and 13.69%, respectively, using the enzymatic method. The individuality index (II) was 0.32 for the Jaffe's method and 0.31 for the enzymatic method. The average RCV calculated bilaterally in the 95% confidence interval for the Jaffe's and enzymatic methods were 14.26 and 13.43, respectively.
Conclusions: This manuscript has underlined the fact that the II of creatinine is less than 0.6 indicating that the use of population-based reference intervals is limited, and interpretation of the RCV and analysis might be a more objective approach. Taken together, these results suggest that it could be valuable to calculate biological variation correctly and increase clinical awareness.