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Insulin-like Growth Factor 1 (IGF-1), Pediatric With Z Score (Endocrine Sciences)
IGF-1 measurements can be useful when evaluating patients of gestational age1 who are suspected of being (1) growth hormone-deficient2 or (2) acromegalic.3
Plasma specimens may produce falsely elevated or decreased results. The IGF-1 reference intervals by pubertal Tanner stages reflect ranges and means based on asymmetric curves. Z scores are calculated based on the asymmetric curves with transformed data. Patient gender and date of birth must be provided in order to calculate a z score. Z scores will not be calculated for patients younger than three years or older than 18 years.
Blocking radioimmunoassy (RIA) after acid:alcohol extraction
Insulin-like growth factor 1 (IGF-1) is a polypeptide hormone that can affect growth-promoting activity and glucose metabolism. IGF-1 exists in a three-subunit complex form, with IGF-1 or IGF-2 (υ-subunit), IGFBP-3 (β-subunit), and acid labile subunit (ALS) (α-subunit). Samples are acid:ethanol extracted to remove IGF-1 from the complex, resulting in a consistent IGF-1 measurement, even with variable binding protein levels. The extracted sample is then analyzed by radioimmunoassay using a highly specific antibody.4
0.1 mL (Note: This volume does not allow for repeat testing.)
Serum must be separated from cells within 45 minutes of venipuncture. Send serum in a plastic transport tube. Transfer specimen to a plastic transport tube before freezing. To avoid delays in turnaround time when requesting multiple tests on frozen specimens, please submit separate frozen specimens for each test requested.
Freeze. Stable for two days at room temperature or refrigerated. Stable for two years frozen.
Causes for Rejection
Specimen not serum