title: Serum IGF-I measured by four different immunoassays in patients with adult GH deficiency or acromegaly and in a control population.
abstract: BACKGROUND
  IGF-I is a useful tool in GH disorders diagnosis, however, the use of commercially available kits needs to be validated.
  
  
  OBJECTIVE
  To validate the use of serum IGF-I concentrations measured by four immunoassays in the diagnosis of adult GH deficiency and acromegaly.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  Fifty GH-deficient (GHD) patients, 41 acromegaly patients and 405 controls.
  
  
  METHODS
  Serum IGF-I concentrations were measured by four commercial immunoassays: (1) RIA-NICHOLS; (2) ICMA-IMMULITE; (3) IRMA-IMMUNOTECH; and (4) non-extraction-IRMA-DSL. Reference values were established from the control population in six age groups. Individual results were transformed to standard deviation score (SD score) from the age-related reference population and reference data provided by each assay manufacturer. Diagnostic sensitivity for GH deficiency was calculated.
  
  
  RESULTS
  IGF-I measured by the four assays differed significantly. In controls, assay 2 yielded the lowest results, followed by assays 1, 3 and 4 (P < 0.0001 for all comparisons). IGF-I declined with age, but no sex-related differences were observed. When IGF-I was standardized with respect to reference data obtained from the manufacturers, it showed better sensitivity in assays 1 and 2, than with our controls (65%vs. 77.5% and 58%vs. 70%, respectively) for GHD diagnosis. With assays 3 and 4, higher sensitivity was obtained when standardized with our controls (62%vs. 52% and 56%vs. 36%, respectively). In acromegaly, IGF-I was > 2 SD score with all assays.
  
  
  CONCLUSIONS
  IGF-I SD score for GHD diagnosis differed according to the normative data used. All assays proved to be useful for active acromegaly diagnosis.
authors.affiliation: Department of Clinical Biochemistry, Hospital Universitari Germans Trias i Pujol, 08916 Badalona, Barcelona, Spain. mgranada.germanstrias@gencat.net
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Granada
authors.forename: Angels
authors.initials: A
authors.lastname: Ulied
authors.forename: Felipe F
authors.initials: FF
authors.lastname: Casanueva
authors.forename: Antonio
authors.initials: A
authors.lastname: Pico
authors.forename: Tomas
authors.initials: T
authors.lastname: Lucas
authors.forename: Elena
authors.initials: E
authors.lastname: Torres
authors.forename: Anna
authors.initials: A
authors.lastname: Sanmartí
mesh_terms: D000172:Acromegaly / Q000097:blood* / Q000378:metabolism; D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D003430:Cross-Sectional Studies; D005260:Female; D019382:Human Growth Hormone / Q000172:deficiency*; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012727:Sex Characteristics; D055815:Young Adult
chemical_list: D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I