This communication is a review of the analytical characteristics described in the literature. We monitored precision of measurement, uncertainty of calibration values, comparability of both commonly used PENIA and PETIA methods. While the precision of both methods is comparable, method PETIA provides a higher analytical range of measurement, however the uncertainty of calibration in PETIA is too higher specially for the clinically most important concentration range. However, precision of cystain C measurement is commonly lower than creatinine serum measurement. PENIA results are significantly lower than PETIA results. In accordance with this fact also reference ranges of PENIA are lower in comparison with PETIA. A reason for these differences is different calibration. The reference interval for adults is independent of sex, age and ethnicity. Children’s reference ranges are higher especially immediately after birth, but the concentration declines very rapidly after birth to concentrations comparable with the adult population.Above the age of fifty years we may observe a mild increase of reference values. PETIA and PENIA methods do not significantly suffer from interference and the PENIA method is more resistant. No influence of muscle mass, alcohol, smoking and changes of hormonal status are described.

        Key words: cystatin C, analytical characteristics, interference, biological influences, reference intervals.