TY - JOUR

T1 - Characteristics and reference ranges of Insulin-Like Growth Factor-I measured with a commercially available immunoassay in 724 healthy adult Caucasians

AU - Andreassen, Mikkel

AU - Nielsen, Kaspar

AU - Raymond, Ilan

AU - Kristensen, Lars Østergaard

AU - Faber, Jens

AU - Andreassen, Mikkel

AU - Nielsen, Kaspar Rosengreen

AU - Raymond, Ilan

AU - Kristensen, Lars Østergaard

AU - Faber, Jens

N1 - Keywords: Adult; Aged; Aged, 80 and over; Blood Specimen Collection; European Continental Ancestry Group; Female; Health; Humans; Immunoassay; Insulin-Like Growth Factor I; Male; Middle Aged; Reagent Kits, Diagnostic; Reference Standards; Reference Values; Sex Characteristics; Young Adult

PY - 2009

Y1 - 2009

N2 - BACKGROUND AND OBJECTIVE: Measurements of Insulin-Like Growth Factor-I (IGF-I) play a pivotal role in the evaluation of the growth hormone-IGF-I axis. Due to assay variation IGF-I reference ranges are assay specific. We provide serum IGF-I reference ranges for adult men and women obtained by a commercially available assay. METHOD: IGF-I was measured by an enzyme-linked immunosorbent assay (R&D Systems). Assay precision was evaluated in low, medium and high IGF-I pools and in single samples from outpatients. The reference ranges were obtained in 724 healthy Caucasians, mean age 48 years (range 19-91). RESULTS: IGF-I was measured higher in serum compared to plasma samples (p<0.001, R2=0.96). To convert EDTA plasma values to serum values a factor of 1.22 was calculated. The intraassay coefficients of variation (CV) for the low: 56.4+/-2.7 ng/mL, medium: 179.7+/-5.9 ng/mL and high pool: 445.61+/-3.2 ng/mL (mean 1 SD) were 5, 3 and 3%. Interassays CVs for the low, medium and high pool varied between 7-10, 5-7, and 6-9%. Reproducibility between 4 different lots showed a intraclass CV of 0.99 (95%CI 0.98-0.96). Logarithmically transformed IGF-I levels were linearly associated with age with a 13% reduction in IGF-I per decade in females and 11% in males. CONCLUSION: We have provided IGF-I reference ranges obtained by an assay that showed variations and reproducibility that was considered of sufficient high quality for clinical and scientific use.

AB - BACKGROUND AND OBJECTIVE: Measurements of Insulin-Like Growth Factor-I (IGF-I) play a pivotal role in the evaluation of the growth hormone-IGF-I axis. Due to assay variation IGF-I reference ranges are assay specific. We provide serum IGF-I reference ranges for adult men and women obtained by a commercially available assay. METHOD: IGF-I was measured by an enzyme-linked immunosorbent assay (R&D Systems). Assay precision was evaluated in low, medium and high IGF-I pools and in single samples from outpatients. The reference ranges were obtained in 724 healthy Caucasians, mean age 48 years (range 19-91). RESULTS: IGF-I was measured higher in serum compared to plasma samples (p<0.001, R2=0.96). To convert EDTA plasma values to serum values a factor of 1.22 was calculated. The intraassay coefficients of variation (CV) for the low: 56.4+/-2.7 ng/mL, medium: 179.7+/-5.9 ng/mL and high pool: 445.61+/-3.2 ng/mL (mean 1 SD) were 5, 3 and 3%. Interassays CVs for the low, medium and high pool varied between 7-10, 5-7, and 6-9%. Reproducibility between 4 different lots showed a intraclass CV of 0.99 (95%CI 0.98-0.96). Logarithmically transformed IGF-I levels were linearly associated with age with a 13% reduction in IGF-I per decade in females and 11% in males. CONCLUSION: We have provided IGF-I reference ranges obtained by an assay that showed variations and reproducibility that was considered of sufficient high quality for clinical and scientific use.

U2 - 10.3109/00365510903165477

DO - 10.3109/00365510903165477

M3 - Journal article

C2 - 19675969

VL - 69

SP - 880

EP - 885

JO - Scandinavian Journal of Clinical & Laboratory Investigation

JF - Scandinavian Journal of Clinical & Laboratory Investigation

SN - 0036-5513

IS - 8

ER -