title: Higher serum beta2-microglobulin levels are associated with better survival in chronic hemodialysis patients: a reverse epidemiology.
abstract: OBJECTIVE
  beta2-Microglobulin (beta2-M) has been considered a surrogate marker of putative mid-molecular weight (MW) uremic toxins, compounds difficult to dialyze by low-flux dialysis membranes. This study was performed to evaluate the relationship between serum beta2-M and survival of chronic hemodialysis (CHD) patients and the association of beta2-M levels and factors associated with mortality.
  
  
  METHODS
  Part I of this study is a retrospective cohort evaluation that determined the relationship between beta2-M and mortality, and Part II is a cross-sectional study that evaluated the relationship between beta2-M and factors associated with mortality. Laboratory parameters, including beta2-M, albumin, prealbumin, creatinine, blood urea nitrogen (BUN), high-sensitivity C-reactive protein (hs-CRP), lipid battery, KT/V, and normalized protein nitrogen appearance (nPNA), were reviewed in Part I and measured in Part II. Clinical and demographic data, including age, sex, duration of hemodialysis, presence of cardiovascular disease, and presence of diabetes mellitus, were also recorded.
  
  
  RESULTS
  Part I: During the follow-up period of 5 years, there were 95 all-cause deaths among the 289 patients. Comparison of survivors and non-survivors indicated that serum beta2-M was higher in survivors (36.8 ± 12.3 vs. 32.6 ± 13.2 µg/ml, p = 0.009). Kaplan-Meier analysis indicated that all-cause mortality in the lower beta2-M group was significantly higher compared to the higher beta2-M group (p < 0.0001). Multivariate Cox regression analyses indicated elevated beta2-M levels were significantly associated with lower mortality rate (relative risk: 0.608; 95% CI: 0.37 to 0.99; p = 0.046). Part II: The mean serum beta2-M concentration was 37.1 ± 14.4 µg/ml. Univariate analysis indicated that beta2-M was positively correlated with nPNA, duration of HD, BMI, and the concentrations of creatinine, albumin, BUN, and hs-CRP, but was negatively correlated with HDL-C concentration. Multiple regression analysis indicated that levels of nPNA (p < 0.001), duration of hemodialysis (p < 0.001), creatinine (p < 0.001), albumin (p = 0.006), BUN (p = 0.011), and HDL-C (p = 0.038) were independently associated with serum beta2-M concentration.
  
  
  CONCLUSIONS
  Our results showed that higher serum beta2-M levels are associated with better survival in CHD patients and that nutritional status might be an independent predictor of serum beta2-M concentration in these patients.
authors.affiliation: Department of Internal Medicine,University of Ulsan College of Medicine, Seoul, South Korea.
authors.forename: K M
authors.initials: KM
authors.lastname: Kim
authors.forename: S-S
authors.initials: SS
authors.lastname: Kim
authors.forename: H
authors.initials: H
authors.lastname: Kim
authors.forename: T
authors.initials: T
authors.lastname: Koo
authors.forename: E Y
authors.initials: EY
authors.lastname: Im
authors.forename: S B
authors.initials: SB
authors.lastname: Kim
mesh_terms: D000328:Adult; D000368:Aged; D001806:Blood Urea Nitrogen; D015992:Body Mass Index; D002097:C-Reactive Protein / Q000032:analysis; D005260:Female; D006801:Humans; D007676:Kidney Failure, Chronic / Q000097:blood* / Q000401:mortality; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D006435:Renal Dialysis / Q000401:mortality*; D012189:Retrospective Studies; D012709:Serum Albumin / Q000032:analysis; D001613:beta 2-Microglobulin / Q000097:blood*
chemical_list: D012709:Serum Albumin; D001613:beta 2-Microglobulin; D002097:C-Reactive Protein