Serum IGF-I measured by four different immunoassays in patients with adult GH deficiency or acromegaly and in a control population.
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.
Granada
Maria Luisa
ML
Department of Clinical Biochemistry, Hospital Universitari Germans Trias i Pujol, 08916 Badalona, Barcelona, Spain. mgranada.germanstrias@gencat.net
Ulied
Angels
A
Casanueva
Felipe F
FF
Pico
Antonio
A
Lucas
Tomas
T
Torres
Elena
E
Sanmartí
Anna
A
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
D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I