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Serum IGF‐I measured by four different immunoassays in patients with adult GH deficiency or acromegaly and in a control population

2007; Wiley; Volume: 68; Issue: 6 Linguagem: Inglês

10.1111/j.1365-2265.2007.03120.x

1365-2265

María Luisa Granada, Àngels Ulied, Felipe F. Casanueva, Antonio Picó, Tomás Lúcas, Elena Torres, Anna Sanmartı́,

Neuroendocrine Tumor Research Advances

Summary 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. Design Cross‐sectional study. Patients Fifty GH‐deficient (GHD) patients, 41 acromegaly patients and 405 controls. Measurements 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.