title: Creatine-kinase MB mass: age and sex-associated reference limits in two different platforms that use the same method.
abstract: BACKGROUND
  Recent updated NACB guidelines suggest that troponins are the biomarker of choice for the detection of myocardial necrosis, but the CK-MB mass is still considered an effective and alternative indicator when troponin assays are not available. The aim of the present study was to compare the reliability of two different analytical platforms in establishing the gender-specific 99th percentile for the CK-MB mass.
  
  
  METHODS
  Serum samples collected from healthy subjects were investigated in two different laboratories, LAB 1 (354 subjects: 222 men, 132 women; median age, 40 years, range 19-64 years) and LAB 2 (330 subjects: 224 men, 106 women; median age, 41 years, range 18-71 years), in order to determine the CK-MB mass (microg/L) using the Access((R)) CKMB method (Beckman Coulter), a two-site immunoenzymatic sandwich assay, on UniCel DxI 800 (LAB 1) and Access((R)) 2 (LAB 2) analyzers (Beckman Coulter). The related plasma samples (lithium-heparin) were also evaluated in LAB 2.
  
  
  RESULTS
  Total imprecision (CV%), calculated in control materials, ranged from 6.00 to 9.05 (concentration range, 3.82-36.37) in LAB 1 and from 7.05 to 5.02 in LAB 2 (concentration range, 3.63-34.18). A statistically significant gender-related difference (p<0.05) was found in the whole population studied, values in men being higher than those in women: median=1.86 vs 1.22; 99th percentile=7.64 vs 5.19. The median values in subjects aged 18-28 years (group 1) were lower than those in the other 4 groups (2-5): 1.12 vs 1.59, vs 1.78, vs 1.95 and vs 2.03. The same age-related trend was also observed for CK-MB plasma values, which were comparable to those observed in the matched-serum samples: median 1.12 vs 1.10 (group 1), 1.45 vs 1.50, (group 5).
  
  
  CONCLUSIONS
  The two different analytical platforms provide comparable results. The finding that CK-MB mass values are significantly higher in males than in females represents a relevant information, that will impact on patient classification when a myocardial necrosis has been suspected. Actually, however, numerous assays commercially available, lack of this information.
authors.affiliation: Department of Laboratory Medicine, University-Hospital, Padova, Italy. martina.zaninotto@sanita.padova.it
authors.forename: M
authors.initials: M
authors.lastname: Zaninotto
authors.forename: M M
authors.initials: MM
authors.lastname: Mion
authors.forename: E
authors.initials: E
authors.lastname: Novello
authors.forename: E
authors.initials: E
authors.lastname: Delprete
authors.forename: M
authors.initials: M
authors.lastname: Moretti
authors.forename: M
authors.initials: M
authors.lastname: Plebani
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D052279:Creatine Kinase, MB Form / Q000097:blood*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000175:diagnosis* / Q000201:enzymology; D012737:Sex Factors; D014336:Troponin / Q000097:blood; D055815:Young Adult
chemical_list: D015415:Biomarkers; D014336:Troponin; D052279:Creatine Kinase, MB Form