Determination of free insulin-like growth factor-I in human serum

comparison of ultrafiltration versus direct immunoradiometric assay

J. Frystyk, C. Skjærbæk, P. Ivarsen, René Støving, T. Dall Bek, C. Hagen, H. Ørskov

Publikation: Bidrag til tidsskriftTidsskriftartikelForskningpeer review

Resumé

Udgivelsesdato: 2001-Apr
OriginalsprogEngelsk
TidsskriftGrowth Hormone & IGF Research
Vol/bind11
Udgave nummer2
Sider (fra-til)117-127
ISSN1096-6374
DOI
StatusUdgivet - 2001

Fingeraftryk

Immunoradiometric Assay
Ultrafiltration
Insulin-Like Growth Factor I
Serum
Insulin-Like Growth Factor Binding Protein 2
Insulin-Like Growth Factor Binding Protein 1
Centrifugation
Weight Gain

Citer dette

Frystyk, J. ; Skjærbæk, C. ; Ivarsen, P. ; Støving, René ; Dall Bek, T. ; Hagen, C. ; Ørskov, H. / Determination of free insulin-like growth factor-I in human serum : comparison of ultrafiltration versus direct immunoradiometric assay. I: Growth Hormone & IGF Research. 2001 ; Bind 11, Nr. 2. s. 117-127.
@article{c3b046d06fcd11db81a9000ea68e967b,
title = "Determination of free insulin-like growth factor-I in human serum: comparison of ultrafiltration versus direct immunoradiometric assay",
abstract = "Two fundamentally different methods are currently used for the determination of free insulin-like growth factor-I (IGF-I): ultrafiltration by centrifugation (UF) and direct immunoradiometric assay (IRMA). The aim was to evaluate a commercial IRMA (DSL, Webster, TX, USA) and to compare it with UF. In the IRMA it is recommended that samples be incubated for 2 h at 5;C. When comparing samples (n = 8) incubated for 1 and 2 h, levels increased by 27 +/- 5{\%} (P< 0.0001). When incubating samples at 22;C instead of 5;C, levels increased by 192 +/- 32{\%} (P< 0.0001). Addition of IGF-binding protein-1 (IGFBP-1) to normal sera (n = 6) dose-dependently decreased ultrafiltered free IGF-I only (P< 0.0007). Similarly, UF was more sensitive than IRMA to addition of IGFBP-2 (P< 0.05). In healthy subjects (n = 35) IRMA yielded 20{\%} higher levels than UF (1.09 +/- 0.09 vs 0.91 +/- 0.12 microg/L; P< 0.0001). IRMA and UF yielded similar results in healthy subjects treated with IGF-I (n = 5) or growth hormone (n = 7) and in acromegalic patients (n = 6) before and after somatostatin analogue treatment. However, marked differences were observed in conditions with elevated IGFBP-1 and -2. In type-1 diabetics (n = 23) ultrafiltered free IGF-I was more reduced than IRMA free IGF-I (38 +/- 9 vs 76 +/- 7{\%} of matched controls (n = 13); P< 0.0001). In patients with chronic renal failure (n = 25), IRMA free IGF-I was identical to control levels (n = 13), whereas ultrafiltered free IGF-I was decreased by 51 +/- 7{\%} (P< 0.0001). Similarly, women with anorexia nervosa (n = 9) studied before and after weight gain showed significant changes in ultrafiltered free IGF-I only (P< 0.03). In conclusion, IRMA was not very robust with respect to variations in sample incubation and this may bias results. IRMA generally yielded higher levels than UF, in accordance with the knowledge that IRMA measures free plus readily dissociable IGF-I. IRMA was less affected than UF by added IGFBP-1 and -2, and reductions in free IGF-I were better revealed by UF than IRMA.",
keywords = "Acromegaly, Adult, Anorexia Nervosa, Case-Control Studies, Diabetes Mellitus, Type 1, Female, Growth Hormone, Humans, Hydrogen-Ion Concentration, Immunoradiometric Assay, Insulin-Like Growth Factor Binding Protein 1, Insulin-Like Growth Factor Binding Protein 2, Insulin-Like Growth Factor I, Kidney Failure, Chronic, Male, Middle Aged, Reference Values, Temperature, Ultrafiltration",
author = "J. Frystyk and C. Skj{\ae}rb{\ae}k and P. Ivarsen and Ren{\'e} St{\o}ving and {Dall Bek}, T. and C. Hagen and H. {\O}rskov",
year = "2001",
doi = "10.1054/ghir.2001.0197",
language = "English",
volume = "11",
pages = "117--127",
journal = "Growth Hormone & I G F Research",
issn = "1096-6374",
publisher = "Churchill Livingstone",
number = "2",

}

Determination of free insulin-like growth factor-I in human serum : comparison of ultrafiltration versus direct immunoradiometric assay. / Frystyk, J.; Skjærbæk, C.; Ivarsen, P.; Støving, René; Dall Bek, T.; Hagen, C.; Ørskov, H.

I: Growth Hormone & IGF Research, Bind 11, Nr. 2, 2001, s. 117-127.

Publikation: Bidrag til tidsskriftTidsskriftartikelForskningpeer review

TY - JOUR

T1 - Determination of free insulin-like growth factor-I in human serum

T2 - comparison of ultrafiltration versus direct immunoradiometric assay

AU - Frystyk, J.

AU - Skjærbæk, C.

AU - Ivarsen, P.

AU - Støving, René

AU - Dall Bek, T.

AU - Hagen, C.

AU - Ørskov, H.

PY - 2001

Y1 - 2001

N2 - Two fundamentally different methods are currently used for the determination of free insulin-like growth factor-I (IGF-I): ultrafiltration by centrifugation (UF) and direct immunoradiometric assay (IRMA). The aim was to evaluate a commercial IRMA (DSL, Webster, TX, USA) and to compare it with UF. In the IRMA it is recommended that samples be incubated for 2 h at 5;C. When comparing samples (n = 8) incubated for 1 and 2 h, levels increased by 27 +/- 5% (P< 0.0001). When incubating samples at 22;C instead of 5;C, levels increased by 192 +/- 32% (P< 0.0001). Addition of IGF-binding protein-1 (IGFBP-1) to normal sera (n = 6) dose-dependently decreased ultrafiltered free IGF-I only (P< 0.0007). Similarly, UF was more sensitive than IRMA to addition of IGFBP-2 (P< 0.05). In healthy subjects (n = 35) IRMA yielded 20% higher levels than UF (1.09 +/- 0.09 vs 0.91 +/- 0.12 microg/L; P< 0.0001). IRMA and UF yielded similar results in healthy subjects treated with IGF-I (n = 5) or growth hormone (n = 7) and in acromegalic patients (n = 6) before and after somatostatin analogue treatment. However, marked differences were observed in conditions with elevated IGFBP-1 and -2. In type-1 diabetics (n = 23) ultrafiltered free IGF-I was more reduced than IRMA free IGF-I (38 +/- 9 vs 76 +/- 7% of matched controls (n = 13); P< 0.0001). In patients with chronic renal failure (n = 25), IRMA free IGF-I was identical to control levels (n = 13), whereas ultrafiltered free IGF-I was decreased by 51 +/- 7% (P< 0.0001). Similarly, women with anorexia nervosa (n = 9) studied before and after weight gain showed significant changes in ultrafiltered free IGF-I only (P< 0.03). In conclusion, IRMA was not very robust with respect to variations in sample incubation and this may bias results. IRMA generally yielded higher levels than UF, in accordance with the knowledge that IRMA measures free plus readily dissociable IGF-I. IRMA was less affected than UF by added IGFBP-1 and -2, and reductions in free IGF-I were better revealed by UF than IRMA.

AB - Two fundamentally different methods are currently used for the determination of free insulin-like growth factor-I (IGF-I): ultrafiltration by centrifugation (UF) and direct immunoradiometric assay (IRMA). The aim was to evaluate a commercial IRMA (DSL, Webster, TX, USA) and to compare it with UF. In the IRMA it is recommended that samples be incubated for 2 h at 5;C. When comparing samples (n = 8) incubated for 1 and 2 h, levels increased by 27 +/- 5% (P< 0.0001). When incubating samples at 22;C instead of 5;C, levels increased by 192 +/- 32% (P< 0.0001). Addition of IGF-binding protein-1 (IGFBP-1) to normal sera (n = 6) dose-dependently decreased ultrafiltered free IGF-I only (P< 0.0007). Similarly, UF was more sensitive than IRMA to addition of IGFBP-2 (P< 0.05). In healthy subjects (n = 35) IRMA yielded 20% higher levels than UF (1.09 +/- 0.09 vs 0.91 +/- 0.12 microg/L; P< 0.0001). IRMA and UF yielded similar results in healthy subjects treated with IGF-I (n = 5) or growth hormone (n = 7) and in acromegalic patients (n = 6) before and after somatostatin analogue treatment. However, marked differences were observed in conditions with elevated IGFBP-1 and -2. In type-1 diabetics (n = 23) ultrafiltered free IGF-I was more reduced than IRMA free IGF-I (38 +/- 9 vs 76 +/- 7% of matched controls (n = 13); P< 0.0001). In patients with chronic renal failure (n = 25), IRMA free IGF-I was identical to control levels (n = 13), whereas ultrafiltered free IGF-I was decreased by 51 +/- 7% (P< 0.0001). Similarly, women with anorexia nervosa (n = 9) studied before and after weight gain showed significant changes in ultrafiltered free IGF-I only (P< 0.03). In conclusion, IRMA was not very robust with respect to variations in sample incubation and this may bias results. IRMA generally yielded higher levels than UF, in accordance with the knowledge that IRMA measures free plus readily dissociable IGF-I. IRMA was less affected than UF by added IGFBP-1 and -2, and reductions in free IGF-I were better revealed by UF than IRMA.

KW - Acromegaly

KW - Adult

KW - Anorexia Nervosa

KW - Case-Control Studies

KW - Diabetes Mellitus, Type 1

KW - Female

KW - Growth Hormone

KW - Humans

KW - Hydrogen-Ion Concentration

KW - Immunoradiometric Assay

KW - Insulin-Like Growth Factor Binding Protein 1

KW - Insulin-Like Growth Factor Binding Protein 2

KW - Insulin-Like Growth Factor I

KW - Kidney Failure, Chronic

KW - Male

KW - Middle Aged

KW - Reference Values

KW - Temperature

KW - Ultrafiltration

U2 - 10.1054/ghir.2001.0197

DO - 10.1054/ghir.2001.0197

M3 - Journal article

VL - 11

SP - 117

EP - 127

JO - Growth Hormone & I G F Research

JF - Growth Hormone & I G F Research

SN - 1096-6374

IS - 2

ER -