title: [Source of variations of serum urea levels and consideration of reference interval in urban Chengdu].
abstract: OBJECTIVE
  To determine the serum Urea levels in healthy adults living in urban Chengdu and to identify factors that influence the serum urea levels for the purpose of establishing reference interval.
  
  
  METHODS
  Serum urea levels were determined in 17 787 healthy adults in urban Chengdu who underwent physical examinations. The characteristics of distribution of serum urea levels in the population and its relationships with liver function, renal function, serum glucose, and serum lipid were analyzed.
  
  
  RESULTS
  Increased Crea, Uric, Glu, and HDL-C levels and decreased Glb level were associated with increased serum urea levels, which was independent of the impact of sex and age. The association between serum urea and Crea, Glu, and HDL-C existed in normal healthy adults. Men had higher urea levels than women. Regardless of gender, serum urea increased with age (with a cut off point at 30, 50, 60 and 70 years).
  
  
  CONCLUSIONS
  Serum urea levels in healthy adults living in urban Chengdu vary in different gender and age groups. Serum urea levels are associated with serum Crea, Glu, the HDL-C levels. It is necessary to establish gender and age-specific reference intervals for serum urea.
authors.affiliation: Department of Laboratory Medicine, West China Hospital, Sichuan University, Chengdu 610041, China.
authors.forename: Rui-Xue
authors.initials: RX
authors.lastname: Lü
authors.forename: Yi-Song
authors.initials: YS
authors.lastname: Li
authors.forename: Zhi-Gang
authors.initials: ZG
authors.lastname: Huang
authors.forename: You-Juan
authors.initials: YJ
authors.lastname: Wang
authors.forename: Zhi-Ying
authors.initials: ZY
authors.lastname: Peng
mesh_terms: D000328:Adult; D000368:Aged; D002681:China; D005260:Female; D006801:Humans; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D012016:Reference Values; D014504:Urban Health; D014508:Urea / Q000097:blood*
chemical_list: D014508:Urea