title: A comparison of methods for evaluation of a case of suspected macro-aspartate aminotransferase.
abstract: BACKGROUND
  Macro-aspartate aminotransferase (macroAST) is a high molecular weight form of AST that is usually formed through association with immunoglobulin (Ig) in the circulation. As a result of reduced inactivation, clearance or excretion, AST values are persistently increased. This can lead to problems interpreting these values and diagnosing the patient, especially if clinicians are not aware of this phenomenon.
  
  
  METHODS
  For a case of suspected macroAST, we compared three simple methods: polyethylene glycol precipitation, ultrafiltration, and Ig depletion using protein A and G.
  
  
  RESULTS
  All three methods were consistent with a diagnosis of macroAST.
  
  
  CONCLUSIONS
  The protein A and G method was straightforward and provided unambiguous results. However, given the affinity of protein A and protein G, it likely only detects AST-IgG macrocomplexes.
authors.affiliation: Department of Laboratory Medicine, University of California, San Francisco, Zuckerberg San Francisco General, San Francisco, CA, USA. Electronic address: Xander.VanWijk@ucsf.edu.
authors.forename: Xander M R
authors.initials: XMR
authors.lastname: van Wijk
authors.affiliation: San Francisco Department of Public Health, Zuckerberg San Francisco General, San Francisco, CA, USA.
authors.forename: Catherine A
authors.initials: CA
authors.lastname: Magee
authors.affiliation: Department of Laboratory Medicine, University of California, San Francisco, Zuckerberg San Francisco General, San Francisco, CA, USA.
authors.forename: Alan H B
authors.initials: AHB
authors.lastname: Wu
authors.affiliation: Department of Medicine, University of California, San Francisco, UCSF Liver Center, San Francisco, CA, USA.
authors.forename: Michele M
authors.initials: MM
authors.lastname: Tana
authors.affiliation: Department of Laboratory Medicine, University of California, San Francisco, Zuckerberg San Francisco General, San Francisco, CA, USA.
authors.forename: Kara L
authors.initials: KL
authors.lastname: Lynch
mesh_terms: D001219:Aspartate Aminotransferases / Q000097:blood* / Q000737:chemistry*; D011232:Chemical Precipitation; D005260:Female; D006801:Humans; D007136:Immunoglobulins / Q000097:blood / Q000737:chemistry* / Q000172:deficiency; D011092:Polyethylene Glycols / Q000737:chemistry*; D013205:Staphylococcal Protein A / Q000737:chemistry*; D014462:Ultrafiltration
chemical_list: D007136:Immunoglobulins; D013205:Staphylococcal Protein A; D011092:Polyethylene Glycols; D001219:Aspartate Aminotransferases
keywords: Aspartate aminotransferase; MacroAST; Macroenzyme; Polyethylene glycol; Protein A; Protein G; Ultrafiltration