title: Simple and robust ICP-MS method for simultaneous determination of serum Co and Cr in routine clinical practice.
abstract: BACKGROUND
  Chromium (Cr) and cobalt (Co) metal ions released from orthopedic prostheses, such as metal-on-metal (MoM) bearings, may be related to wear of the bearing surface. These ions may serve as indicators of the in vivo performance of MoM bearing surfaces. We developed a simple and sensitive assay suitable for the simultaneous measurement of serum Cr and Co using inductively coupled plasma-mass spectrometry (ICP-MS) in clinical routine laboratory practice to evaluate analytical performance and clinical utility.
  
  
  METHODS
  We evaluated the linearity, precision, and lower limit of quantification (LOQ) of an ICP-MS method to determine serum Cr and Co concentration in accordance with U.S. Food and Drug Administration guidance for bioanalytical method validation. This method was used to determine the serum Cr and Co levels of 236 clinical samples from 74 patients with MoM hip prosthesis and 51 healthy controls.
  
  
  RESULTS
  The assay showed good linearity (0-20 μg/l, r(2)>0.999) and satisfactory accuracy for all tested concentrations of Cr and Co (%bias, -1.5% to 2.5%, -3.3% to 1.6%, respectively). The CVs for both metal ions were <10% for LOQ (0.02 μg/l Cr, 0.01 μg/l Co) and within 5% for other concentrations (intra- and inter-assay CV, 1.2-2.6 and 1.9-4.4% of Cr; 1.4-2.7 and 1.9-4.7% of Co). The serum Cr and Co concentrations (mean ± SD) were 0.60 ± 0.12 μg/l and 0.29 ± 0.15 μg/l in 51 healthy subjects. In 74 patients (185 serum samples) after HRA (median duration implanted, 48 months; range, 1-138 months), the concentrations of Cr and Co were 2.75 μg/l (range, 0.61-116.80 μg/l) and 1.49 μg/l (range, 0.12-127.80 μg/l), respectively.
  
  
  CONCLUSIONS
  ICP-MS can simultaneously quantify serum Cr and Co levels with suitable analytical performance including a wide analytical range and very low LOQ. This assay will be very useful for evaluating the nutritional status of Cr and Co in healthy humans as well as monitoring the performance of orthopedic prostheses after hip resurfacing arthroplasty.
authors.affiliation: Department of Laboratory Medicine and Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea; Department of Laboratory Medicine, Chonnam National University Medical School and Chonnam National University Hospital, Gwanju, Korea.
authors.forename: Hyun-Jung
authors.initials: HJ
authors.lastname: Choi
authors.affiliation: Department of Orthopedic Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Seung-Jae
authors.initials: SJ
authors.lastname: Lim
authors.affiliation: Department of Orthopedic Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea. Electronic address: ys3.park@samsung.com.
authors.forename: Youn-Soo
authors.initials: YS
authors.lastname: Park
authors.affiliation: Department of Laboratory Medicine and Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea. Electronic address: suddenbz@skku.edu.
authors.forename: Soo-Youn
authors.initials: SY
authors.lastname: Lee
mesh_terms: D000328:Adult; D000368:Aged; D001774:Blood Chemical Analysis; D002857:Chromium / Q000097:blood*; D003035:Cobalt / Q000097:blood*; D005260:Female; D006801:Humans; D008297:Male; D013058:Mass Spectrometry; D008875:Middle Aged; D014481:United States; D014486:United States Food and Drug Administration; D055815:Young Adult
chemical_list: D002857:Chromium; D003035:Cobalt
keywords: Arthroplasty; Chromium; Cobalt; ICP-MS