title: Spurious increase in serum chromogranin A: the role of heterophilic antibodies.
abstract: BACKGROUND
  The aim of the study was to examine the prevalence of heterophilic antibody (HAb) interference on serum chromogranin A (CgA) measurements.
  
  
  METHODS
  Serum CgA was measured in 672 serum samples before and following incubation in heterophilic antibody blocking tubes (HBTs). Results showing more than 3 and 5 SD percentage difference from the original result were considered to be affected by possible or definite HAb interference, respectively. All possible interferences were confirmed or excluded by non-linear or linear dilution tests.
  
  
  RESULTS
  Following HBT treatment, CgA concentrations fell >3 SD percent compared with the original result in seven specimens, six of which also showed non-linear dilution (0.9%). A clinically relevant increase in serum CgA occurred in five patients (0.7%). No samples showed a significant increase of >3 SD percent following HBT treatment.
  
  
  CONCLUSIONS
  Interference from HAb occurred in up to 0.9% of sera tested for serum CgA. If an increased CgA result does not fit the clinical picture, pretreatment of serum in HBT tubes may prevent unwarranted investigations or therapies.
authors.affiliation: Department of Nuclear Medicine, Oncology Institute of Southern Switzerland, Bellinzona, Switzerland. luca.giovanella@eoc.ch
authors.forename: Luca
authors.initials: L
authors.lastname: Giovanella
authors.forename: Luca
authors.initials: L
authors.lastname: Ceriani
mesh_terms: D000328:Adult; D000368:Aged; D000910:Antibodies, Heterophile / Q000097:blood* / Q000276:immunology*; D016477:Artifacts; D053379:Chromogranin A / Q000097:blood* / Q000276:immunology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012680:Sensitivity and Specificity
chemical_list: D000910:Antibodies, Heterophile; D053379:Chromogranin A