RESUMO
Objective To establish normal reference ranges for serum cystatin C (Cys C)in relatively healthy middle-aged and elderly(＞50 years)Chinese individuals.Methods A total of 1087 candidates were consecutively selected and serum Cys-C levels were measured by transmission turbidimetry.Frequency analysis and histogram were used to establish the 95％ confidence reference range according to methods provided by CLSI (C28-A2).Results Based on the definition and verification procedures for clinical laboratory reference ranges(CLSI C28-A2,second edition),Cys-C levels of 1087 participants fell within the range of 0.30-1.55 mg/L;Male participants had higher serum Cys-C levels than female participants(Z=-10.19,P＜0.01).The serum Cys-C level increased with age,regardless of gender(R =0.600,P＜ 0.01).Differences in Cys-C levels between age groups were statistically significant (x2=411.17,P＜ 0.01).The reference ranges of normal serum Cys-C levels for different age groups (50-,55-,60-,65-,70-,75-,) were 0.42-0.98mg/L,0.45-1.04mg/L,0.47-1.34mg/L,0.46-1.38mg/L,0.61-1.33mg/L,0.61-1.28 mg/L,respectively,for males,and 0.39-0.94mg/L,0.42-1.01mg/L,0.40-0.91mg/L,0.46-1.03mg/L,0.57-1.04mg/L,0.55-1.27mg/L,respectively,for females.Conclusions This study established preliminary normal serum Cys-C reference ranges for healthy middle-aged and elderly(＞ 50 years)individuals in this region,which can serve as parameters for disease diagnosis and treatment evaluation.