Determination of biological variation and reference change values of glycated nail proteins

Aim: In the literature, the biological variation values of different analytes in the body fluids such as serum, plasma, and urine have been reported by different study groups. These parameters are useful in revealing the usefulness of the use of the reference intervals belonging to the clinical diagnosis and follow-up analysis. There are considerable data about the use of glycated nail proteins in especially long-term glycemic control monitoring in previous studies. The aim of this study was to contribute to the evaluation of glycated nail proteins analysis test results by determining the within-subject biological variation, between-subject biological variation, individuality index, and reference change values of glycated nail proteins. Materials and Methos: Thirty-two healthy volunteers in both genders (18 female and 14 male), aged 18-45 years and without any disease history, were included in the study. The nail and blood samples from the volunteers involved in the study were taken at 10 different times within a selected 6-monthly time period. The measurement of glycated nail proteins was performed according to the modified spectrophotometric nitro-blue tetrazolium (NBT) method. Results: The within-subject biological variation and between-subject biological variation of glycated nail proteins were 17.59% and 29.01%, respectively. The calculated individuality index value was 0.606; the reference change value showing a clinically significant difference in the individual's serial measurements for a parameter was 55.1% with 95% probability for glycated nail proteins. Conclusions: These results for glycated nail proteins show that the individuality is high and therefore it is clinically more useful to determine the significance of the changes in the assessments made according to the individual's previous results than the use of the reference intervals.