title: Biological variability of thyroid autoantibodies (anti-TPO and anti-Tg) in clinically and biochemically stable patients with autoimmune thyroid disease.
abstract: The biological variation of anti-TPO and anti-Tg autoantibodies was studied in 17 clinically and biochemically stable female patients with autoimmune thyroid disease (AITD), at regular monthly intervals over a period of 6 consecutive months. The mean and standard deviation (SD), within-subject coefficient of variation (CV), between-subject CV, index of individuality, reliability coefficient, and critical differences were as follows: for anti-TPO 238 (197) U/ml, 9.2%, 81.4%, 0.11, 0.96, and 27.6%; and for anti-Tg 1,785 (3,170) U/ml, 6.9%, 174%, 0.04, 0.99, and 22.3%. The data indicate a low within-subject CV, and a high between-subject CV that is particularly pronounced for anti-Tg. The high individuality of both autoantibodies indicates that an isolated result compared to conventional population-based reference intervals is of very little value for diagnosis. Furthermore, the near to 1 reliability coefficient for both autoantibodies correctly classifies the patient with respect to his or her homeostatic mean antibody concentration in a 6-month period of clinical and biochemical stability of thyroid disease. Imprecision goals for anti-TPO and anti-Tg antibodies are attainable with current methodology.
authors.affiliation: Servicio de Bioquímica, Hospital Universitario, Universidad de Salamanca, Salamanca, Spain.
authors.forename: Concepción
authors.initials: C
authors.lastname: González
authors.forename: Monserrat
authors.initials: M
authors.lastname: Hernando
authors.forename: Fernando
authors.initials: F
authors.lastname: Cava
authors.forename: Eva
authors.initials: E
authors.lastname: Herrero
authors.forename: Luis Carlos
authors.initials: LC
authors.lastname: García-Díez
authors.forename: José Alejandro
authors.initials: JA
authors.lastname: Navajo
authors.forename: José Manuel
authors.initials: JM
authors.lastname: González-Buitrago
mesh_terms: D000328:Adult; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007518:Isoantibodies / Q000097:blood*; D013967:Thyroiditis, Autoimmune / Q000276:immunology*
chemical_list: D007518:Isoantibodies; C035678:anti-Thy antibody