title: When an Analytical Interference Is a Useful Diagnostic Tool: Finding Monoclonal Gammopathies in Routine Analysis.
abstract: BACKGROUND
  The daily productivity of a clinical laboratory depends on the large number of interferences that affect analytical accuracy. Obviously, they have always been considered as a very important aspect to keep accuracy under control. Nevertheless, we wondered if this aspect would be beneficial. In this article, we propose a method for finding monoclonal gammopathies that are based on the fact that the presence of paraprotein in the sample may interfere with routine laboratory assays, specifically, with the quantification of uric acid and conjugated bilirubin.
  
  
  METHODS
  Over a 5-month period, we evaluated 18,278 sera samples of patients from primary care. None of them were suspected of having plasma cell dyscrasias (not observed hypercalcemia, renal failure, anemia, and/or lytic bone lesions). Although biochemical findings suggested paraprotein interference, we carried out serum capillary electrophoresis (CE) and quantification of immunoglobulins and serum-free light chains (SFLCs). We also confirmed the results obtained by performing the corresponding immunofixation electrophoresis (IFE). Flow cytometry analyses were conducted for immunophenotypic characterization of plasma cells from these patients.
  
  
  RESULTS
  The proposed detection method allowed us to identify eight patients with previously undiagnosed monoclonal gammopathy.
  
  
  CONCLUSIONS
  The results show that it is possible to use analytical interference for diagnostic purposes, and most importantly, almost all cases were identified at an early stage of the disease, when associated clinical manifestations were not yet observed.
authors.affiliation: Bioquímica Clínica y Patología Molecular, Hospital Clínico Universitario, Valencia, Spain.
authors.forename: Carmen
authors.initials: C
authors.lastname: Quiñones-Torrelo
authors.affiliation: Bioquímica Clínica y Patología Molecular, Hospital Clínico Universitario, Valencia, Spain.
authors.forename: María Pilar
authors.initials: MP
authors.lastname: Villanueva-Gil
authors.affiliation: Bioquímica Clínica y Patología Molecular, Hospital Clínico Universitario, Valencia, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Rodríguez-Muñoz
authors.affiliation: Bioquímica Clínica y Patología Molecular, Hospital Clínico Universitario, Valencia, Spain.
authors.forename: Lidia
authors.initials: L
authors.lastname: Abellán-Tejada
authors.affiliation: Bioquímica Clínica y Patología Molecular, Hospital Clínico Universitario, Valencia, Spain.
authors.forename: Manuel
authors.initials: M
authors.lastname: Aparici-Ibáñez
authors.affiliation: Bioquímica Clínica y Patología Molecular, Hospital Clínico Universitario, Valencia, Spain.
authors.forename: Arturo
authors.initials: A
authors.lastname: Carratalá-Calvo
mesh_terms: D000369:Aged, 80 and over; D001798:Blood Proteins / Q000032:analysis; D003955:Diagnostic Tests, Routine / Q000379:methods*; D019075:Electrophoresis, Capillary; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010265:Paraproteinemias / Q000175:diagnosis*
chemical_list: D001798:Blood Proteins
keywords: analytical interference; detection method; monoclonal gammopathy; unconjugated bilirubin; uric acid