title: Comparison of Free Light Chain Assays:  Freelite and N Latex in Diagnosis, Monitoring, and Predicting Survival in Light Chain Amyloidosis.
abstract: OBJECTIVE
  Measurement of serum free light chains (FLCs) is critical in diagnosis, prognosis, and monitoring treatment responses in light chain (AL) amyloidosis. We compare the Freelite assay (polyclonal antibodies to hidden light chain epitopes), which is the current gold standard, with a new assay: a mixture of monoclonal antibodies to light chain epitopes (N Latex).
  
  
  METHODS
  We collected 240 serum samples from 94 consecutive patients with newly diagnosed AL amyloidosis (at least three serial serum samples during the first 6 months) analyzed at the National Amyloidosis Centre, London, from January 2011 to April 2012. Concordance in detecting abnormal light chain components and hematologic response was assessed at 2, 4, and 6 months.
  
  
  RESULTS
  The κ and λ clonal light chain involvement was 21% and 79%, respectively, with an abnormal κ/λ ratio or detectable protein in 78.7%. Median κ, λ, and difference in involved and uninvolved FLCs by Freelite and N Latex assays were 17.3 vs 16 mg/L (R(2 ) = 0.91), 48.8 vs 52.6 mg/L (R(2) = 0.52), and 43.2 vs 39.1 mg/L, respectively. Discordant κ/λ ratios at presentation were as follows: 10 of 90 abnormal by Freelite/normal by N Latex and 11 of 90 abnormal by N Latex/normal by Freelite.
  
  
  CONCLUSIONS
  Both FLC assays show good correlation in detecting the abnormal light chain subtype with discordance in absolute values and thus are not interchangeable.
authors.affiliation: From the National Amyloidosis Centre, University College London Medical School, Royal Free Hospital Campus, London, United Kingdom.
authors.forename: Shameem
authors.initials: S
authors.lastname: Mahmood
authors.affiliation: Clinical Biochemistry Department, Royal Free London Foundation Trust, London, United Kingdom.
authors.forename: Nancy L
authors.initials: NL
authors.lastname: Wassef
authors.affiliation: Clinical Biochemistry Department, Royal Free London Foundation Trust, London, United Kingdom.
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Salter
authors.affiliation: From the National Amyloidosis Centre, University College London Medical School, Royal Free Hospital Campus, London, United Kingdom.
authors.forename: Sajitha
authors.initials: S
authors.lastname: Sachchithanantham
authors.affiliation: From the National Amyloidosis Centre, University College London Medical School, Royal Free Hospital Campus, London, United Kingdom.
authors.forename: T
authors.initials: T
authors.lastname: Lane
authors.affiliation: From the National Amyloidosis Centre, University College London Medical School, Royal Free Hospital Campus, London, United Kingdom.
authors.forename: D
authors.initials: D
authors.lastname: Foard
authors.affiliation: From the National Amyloidosis Centre, University College London Medical School, Royal Free Hospital Campus, London, United Kingdom.
authors.forename: Carol J
authors.initials: CJ
authors.lastname: Whelan
authors.affiliation: From the National Amyloidosis Centre, University College London Medical School, Royal Free Hospital Campus, London, United Kingdom.
authors.forename: Helen J
authors.initials: HJ
authors.lastname: Lachmann
authors.affiliation: From the National Amyloidosis Centre, University College London Medical School, Royal Free Hospital Campus, London, United Kingdom.
authors.forename: Julian D
authors.initials: JD
authors.lastname: Gillmore
authors.affiliation: From the National Amyloidosis Centre, University College London Medical School, Royal Free Hospital Campus, London, United Kingdom.
authors.forename: Philip N
authors.initials: PN
authors.lastname: Hawkins
authors.affiliation: From the National Amyloidosis Centre, University College London Medical School, Royal Free Hospital Campus, London, United Kingdom a.wechalekar@ucl.ac.uk.
authors.forename: Ashutosh D
authors.initials: AD
authors.lastname: Wechalekar
mesh_terms: D000368:Aged; D000686:Amyloidosis / Q000175:diagnosis*; D000911:Antibodies, Monoclonal; D005260:Female; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D007147:Immunoglobulin Light Chains / Q000097:blood*; D000075363:Immunoglobulin Light-chain Amyloidosis; D008297:Male; D008875:Middle Aged; D012680:Sensitivity and Specificity
chemical_list: D000911:Antibodies, Monoclonal; D007147:Immunoglobulin Light Chains
keywords: Freelite; Light chain amyloidosis; Light chain assays; N Latex; Prognostic utility