title: Comparison of chromogenic and ELISA functional C1 inhibitor tests in diagnosing hereditary angioedema.
abstract: BACKGROUND
  Measuring functional C1 inhibitor (C1 INH) with chromogenic or ELISA methods can confirm a diagnosis of hereditary angioedema (HAE) due to C1 INH deficiency. Previous studies found differences in the agreement of these assays.
  
  
  OBJECTIVE
  To evaluate the agreement between chromogenic or ELISA methods in the context of an observational study.
  
  
  METHODS
  Patients with previously confirmed HAE underwent functional C1 INH testing. These patients contacted first-degree relatives (parents, siblings, or offspring) not previously evaluated for HAE, who underwent a panel of complement testing, including for functional C1 INH.
  
  
  RESULTS
  Overall, 31 patients with HAE and 46 untested relatives enrolled. Of 46 relatives, 14 (30.4%) were newly diagnosed with HAE based on their laboratory results. Among the 31 patients previously confirmed with HAE, all had low functional C1 INH according to the chromogenic method, whereas 22 (71.0%) had low, 7 (22.6%) had equivocal, and 2 (6.5%) had normal functional C1 INH according to the ELISA method. In the 14 newly diagnosed relatives, all had low functional C1 INH according to the chromogenic method, whereas 11 (78.5%) had low and 3 (21.4%) had equivocal results according to the ELISA method.
  
  
  CONCLUSIONS
  Despite the apparent discordance in the ELISA and chromogenic assays in a small number of patients, both were useful in measuring functional C1 INH. To establish the diagnosis of HAE due to C1 INH deficiency, functional C1 INH results should be interpreted in combination with family and clinical history, and with other complement tests.
authors.affiliation: Institute for Asthma and Allergy, Chevy Chase, Md. Electronic address: hl@allergyasthma.us.
authors.forename: H Henry
authors.initials: HH
authors.lastname: Li
authors.affiliation: Department of Medicine, Division of Clinical Immunology, Mount Sinai School of Medicine, New York, NY.
authors.forename: Paula
authors.initials: P
authors.lastname: Busse
authors.affiliation: Allergy and Asthma Research Association, Research Center, Dallas, Tex.
authors.forename: William R
authors.initials: WR
authors.lastname: Lumry
authors.affiliation: Complement Laboratory, National Jewish Health, Denver, Colo.
authors.forename: Ashley
authors.initials: A
authors.lastname: Frazer-Abel
authors.affiliation: ViroPharma Incorporated (part of the Shire Group of Companies), Exton, Pa.
authors.forename: Howard
authors.initials: H
authors.lastname: Levy
authors.affiliation: ViroPharma Incorporated (part of the Shire Group of Companies), Exton, Pa.
authors.forename: Tamara
authors.initials: T
authors.lastname: Steele
authors.affiliation: ViroPharma Incorporated (part of the Shire Group of Companies), Exton, Pa.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Dayno
authors.affiliation: Department of Medicine, Division of Rheumatology, Allergy and Immunology, University of California-San Diego, La Jolla, Calif.
authors.forename: Marc
authors.initials: M
authors.lastname: Riedl
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D054179:Angioedemas, Hereditary / Q000097:blood / Q000175:diagnosis* / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D050718:Complement C1 Inhibitor Protein / Q000032:analysis*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D055815:Young Adult
chemical_list: D050718:Complement C1 Inhibitor Protein
keywords: C1 inhibitor; Complement testing; Hereditary angioedema