title: Factors other than the glomerular filtration rate that determine the serum beta-2-microglobulin level.
abstract: BACKGROUND
  β2-microglobulin has been increasingly investigated as a diagnostic marker of kidney function and a prognostic marker of adverse outcomes. To date, non-renal determinants of β2-microglobulin levels have not been well described. Non-renal determinants are important for the interpretation and appraisal of the diagnostic and prognostic value of any endogenous kidney function marker.
  
  
  METHODS
  This cross-sectional analysis was performed within the framework of the www.seniorlabor.ch study, which includes subjectively healthy individuals aged ≥ 60 years. Factors known or suspected to have a non-renal association with kidney function markers were investigated for a non-renal association with serum β2-microglobulin. As a marker of kidney function, the Berlin Initiative Study equation 2 for the estimation of the estimated glomerular filtration rate (eGFR(BIS2)) in the elderly was employed.
  
  
  RESULTS
  A total of 1302 participants (714 females and 588 males) were enrolled in the study. The use of a multivariate regression model adjusting for age, gender and kidney function (eGFR(BIS2)) revealed age, male gender, and C-reactive protein level to be positively associated with β2-microglobulin levels. In addition, there was an inverse non-renal relationship between systolic blood pressure, total cholesterol and current smoking status. No association with markers of diabetes mellitus, body stature, nutritional risk, thyroid function or calcium and phosphate levels was observed.
  
  
  CONCLUSIONS
  Serum β2-microglobulin levels in elderly subjects are related to several non-renal factors. These non-renal factors are not congruent to those known from other markers (i.e. cystatin C and creatinine) and remind of classical cardiovascular risk factors.
authors.affiliation: Division of Endocrinology, Diabetes and Clinical Nutrition and Department of General Internal Medicine, University Hospital and University of Bern, Bern, Switzerland.
authors.forename: Zeno
authors.initials: Z
authors.lastname: Stanga
authors.forename: Stefan
authors.initials: S
authors.lastname: Nock
authors.forename: Pedro
authors.initials: P
authors.lastname: Medina-Escobar
authors.forename: Urs E
authors.initials: UE
authors.lastname: Nydegger
authors.forename: Martin
authors.initials: M
authors.lastname: Risch
authors.forename: Lorenz
authors.initials: L
authors.lastname: Risch
mesh_terms: D000367:Age Factors; D000368:Aged; D015415:Biomarkers / Q000097:blood*; D001794:Blood Pressure; D002097:C-Reactive Protein / Q000378:metabolism*; D002784:Cholesterol / Q000097:blood; D003430:Cross-Sectional Studies; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007668:Kidney / Q000502:physiology / Q000503:physiopathology; D007677:Kidney Function Tests; D008297:Male; D015999:Multivariate Analysis; D011379:Prognosis; D012044:Regression Analysis; D012737:Sex Factors; D012907:Smoking; D001613:beta 2-Microglobulin / Q000097:blood*
chemical_list: D015415:Biomarkers; D001613:beta 2-Microglobulin; D002097:C-Reactive Protein; D002784:Cholesterol