title: Reference intervals and factors contributing to serum cystatin C levels in a Chinese population.
abstract: BACKGROUND
  Serum cystatin C (Cys-C), an inhibitor of cysteine proteases, has been suggested as an ideal biomarker of glomerular filtration rate (GFR).
  
  
  OBJECTIVE
  The objective of this study was to describe the reference intervals of serum Cys-C and identify factors associated with serum Cys-C or its variability, including age, gender, creatinine (Crea), blood urea nitrogen (BUN), and uric acid (UA).
  
  
  METHODS
  Serum Cys-C, Crea, BUN, and UA were measured in 4,517 healthy participants aged 8-89 years attending our hospital. Serum Cys-C was analyzed using a latex-enhanced immunoturbidimetric method. Crea were tested by picric acid jaffe method, BUN, and UA by kinetic UV assays.
  
  
  RESULTS
  The predominant characteristic of Cys-C distribution was that Cys-C concentration in age ≥60 years group was the highest (P < 0.05). The differences of Cys-C concentration between males and females existed for subjects aged from 30 to 59 years (P < 0.05). In a multiple model adjusted only for gender and age, gender (β = 0.007) has stronger effect on Cys-C levels, compared with age (β = 0.003). The clinical variables, comprised of age, gender, Crea, BUN, and UA, involved in the fully adjusted equation accounted for 37.6% of variation of Cys-C.
  
  
  CONCLUSIONS
  Ninety-five percent reference intervals for healthy population were partitioned into three categories only by age, 0.59-1.07 mg/L for subjects aged 19-59 years; 0.74-1.14 mg/L for the older aged ≥60 years; and 0.63-1.11 mg/L for children aged ≤18 years. Serum Cys-C is significantly related to gender, age, UA, Crea, and BUN. Besides, there are still other factors contributing to variation of Cys-C levels.
authors.affiliation: Department of Laboratory Medicine, West China Hospital, Sichuan University, Chengdu, P.R. China.
authors.forename: Dong-Dong
authors.initials: DD
authors.lastname: Li
authors.forename: Meng-Na
authors.initials: MN
authors.lastname: Zou
authors.forename: Xin
authors.initials: X
authors.lastname: Hu
authors.forename: Mei
authors.initials: M
authors.lastname: Zhang
authors.forename: Cheng-Yao
authors.initials: CY
authors.lastname: Jia
authors.forename: Chuan-Min
authors.initials: CM
authors.lastname: Tao
authors.forename: Lan-Lan
authors.initials: LL
authors.lastname: Wang
authors.forename: Bin-Wu
authors.initials: BW
authors.lastname: Ying
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D044466:Asian People; D001806:Blood Urea Nitrogen; D002648:Child; D002681:China; D003404:Creatinine / Q000097:blood; D055316:Cystatin C / Q000097:blood*; D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012727:Sex Characteristics; D014527:Uric Acid / Q000097:blood; D055815:Young Adult
chemical_list: C525030:CST3 protein, human; D055316:Cystatin C; D014527:Uric Acid; D003404:Creatinine