Core Laboratory
13. Insulin-Like Growth Factor-1 (IGF-1)
In order to dissociate IGF-1 from the IGFBPs, the samples must be diluted in an acidic buffer. The diluted samples are then pipetted into the assay tubes. The IGF-1 antiserum containing an excess of IGF-II is dissolved in a buffer, which is able to neturalize the acidic samples. After the IGF-1 antibody solution has neutralized the samples, the excess IGF-II occupies the IGF binding sites of the binding proteins, thus allowing the measurement of free IGF-1. With this method, the IGFBPs are not removed, but their function and therefore their interference in the assay is neutralized. Due to the extremely low cross-reactivity of the IGF-1 antibody with IGF-II, excess IGF-II does not disturb the interaction on the first antibody with IGF-1 or IGF-1 tracer. The assay is then continued like a conventional RIA using a second antibody for the separation of bound and free tracer.
Reference:
- Baxter RC: The somatomedins: insulin-like growth factors. Adv Clin Chem: 25: 49-115, 1986
Interassay coefficient of variation (CV):
Sample 1 = 2.4% (n=10, mean=42)
Sample 2 = 5.6% (n=10, mean=266)
Sample 3 = 4.8% (n=10, mean=497)
For more information, please contact the Core Laboratory manager or director.