Insulin-like Growth Factor 1 (IGF-1), Pediatric With Z Score (Endocrine Sciences)

CPT: 84305
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Test Details

Use

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

Limitations

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.

Methodology

Blocking radioimmunoassy (RIA) after acid:alcohol extraction

Additional Information

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

Specimen Requirements

Specimen

Serum, frozen

Volume

0.5 mL

Minimum Volume

0.1 mL (Note: This volume does not allow for repeat testing.)

Container

Red-top tube or gel-barrier tube

Collection

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.

Storage Instructions

Freeze. Stable for two days at room temperature or refrigerated. Stable for two years frozen.

Causes for Rejection

Specimen not serum

Clinical Information

Footnotes

1. Lee PA, Chernausek SD, Hokken-Koelega ACS, et al. International Small for Gestational Age Advisory Board Consensus Development Conference Statement: Management of short children born small for gestational age. April 24-Oct 1, 2011. Pediatrics. 2003; 111(6):1253-1261.12777538
2. GH Research Society. Consensus guidelines for the diagnosis and treatment of the GH Research Society. J Clin Endocrinol Metab. 2000; 85(11):3990-3993.11095419
3. Giustina A, Chanson P, Bronstein MD, et al. A consensus on criteria for cure of acromegaly. J Clin Endocrinol Metab. 2010; 95(7):3141-3148.20410227
4. Alberti C, Chevenne D, Mercat I, et al. Serum concentrations of insulin-like growth factor (IGF-1) and IGF binding protein-3 (IGFBP-3), IGF-1/IGFBP-3 ratio, and markers of bone turnover: Reference values for French children and adolescents and Z-score comparability with other references. Clin Chem. 2011; 57(10):1424-1435.21865482

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
503660 IGF-1, Pediatric with Z-Score 500486 IGF-1(BL) ng/mL 2484-4
503660 IGF-1, Pediatric with Z-Score 503668 IGF-1 Z-Score for Tanner 1 73561-3
503660 IGF-1, Pediatric with Z-Score 503669 IGF-1 Z-Score for Tanner 2 73561-3
503660 IGF-1, Pediatric with Z-Score 503670 IGF-1 Z-Score for Tanner 3 73561-3
503660 IGF-1, Pediatric with Z-Score 503671 IGF-1 Z-Score for Tanner 4 & 5 73561-3

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