Insulin-like growth factor-I in cats: validation of an enzyme-linked immunosorbent assay and determination of biological variation

Emma M. Strage, Elvar Theodorsson, Bodil Ström Holst, Inger Lilliehöök, Moira Lewitt

Research output: Contribution to journalArticle

Abstract

BackgroundInsulin-like growth factor I (IGF-I) measurements are used in veterinary medicine for diagnosing growth hormone disorders. IGF-I assays are subject to interference by IGF-binding proteins (IGFBP) which may not be efficiently removed by standard extraction methods. Adding excess IGF-II during analysis may improve accuracy.
ObjectivesThe purpose of the study was to validate a commercial human IGF-I ELISA which uses excess IGF-II for feline samples and to evaluate biologic variation.
MethodsPrecision was determined by calculating the coefficient of variation (CV). Accuracy was determined by recovery after removal of IGFBP, addition of IGF-I, and linear dilution after the addition of IGFBP. Biologic variation was determined by repeated sampling in 7 cats.
ResultsThere was interference by IGFBP in the high measuring range, resulting in falsely low IGF-I concentrations. This was overcome by the addition of high concentrations of IGF-II. Untreated serum had a measured/expected ratio of 98–115% compared to serum where IGFBP had been removed. Recovery after the addition of IGF-I was 83–112%. Inter- and intra-assay CVs ranged from 2.4% to 5.0% which is within the minimum acceptance criteria based on biologic variation. The reference interval of IGF-I was wide (90–1207 ng/mL) and there was a significant association between body weight and ln IGF-I (P < .000001).
ConclusionsThis human ELISA is suitable for feline samples, but interfering IGFBP can cause falsely low concentrations. It is recommended to dilute samples such that IGF-I is < 28 ng/mL on the standard curve to grant for sufficient IGF-II for binding of interferent IGFBP.
Original languageEnglish
Pages (from-to)542-551
Number of pages10
JournalJournal of Veterinary Clinical Pathology
Volume44
Issue number4
DOIs
Publication statusPublished - 2015

Fingerprint

insulin-like growth factor I
Insulin-Like Growth Factor I
Insulin-Like Growth Factor Binding Proteins
insulin-like growth factor binding proteins
Cats
Enzyme-Linked Immunosorbent Assay
enzyme-linked immunosorbent assay
cats
insulin-like growth factor II
Insulin-Like Growth Factor II
Felidae
assays
Growth Disorders
sampling
Veterinary Medicine
Serum
somatotropin
growth factors
veterinary medicine
Growth Hormone

Keywords

  • growth hormone disorders
  • insulin-like growth factor-binding proteins
  • size-exclusion chromatography

Cite this

Strage, Emma M. ; Theodorsson, Elvar ; Ström Holst, Bodil ; Lilliehöök, Inger ; Lewitt, Moira. / Insulin-like growth factor-I in cats : validation of an enzyme-linked immunosorbent assay and determination of biological variation. In: Journal of Veterinary Clinical Pathology. 2015 ; Vol. 44, No. 4. pp. 542-551.
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title = "Insulin-like growth factor-I in cats: validation of an enzyme-linked immunosorbent assay and determination of biological variation",
abstract = "BackgroundInsulin-like growth factor I (IGF-I) measurements are used in veterinary medicine for diagnosing growth hormone disorders. IGF-I assays are subject to interference by IGF-binding proteins (IGFBP) which may not be efficiently removed by standard extraction methods. Adding excess IGF-II during analysis may improve accuracy.ObjectivesThe purpose of the study was to validate a commercial human IGF-I ELISA which uses excess IGF-II for feline samples and to evaluate biologic variation.MethodsPrecision was determined by calculating the coefficient of variation (CV). Accuracy was determined by recovery after removal of IGFBP, addition of IGF-I, and linear dilution after the addition of IGFBP. Biologic variation was determined by repeated sampling in 7 cats.ResultsThere was interference by IGFBP in the high measuring range, resulting in falsely low IGF-I concentrations. This was overcome by the addition of high concentrations of IGF-II. Untreated serum had a measured/expected ratio of 98–115{\%} compared to serum where IGFBP had been removed. Recovery after the addition of IGF-I was 83–112{\%}. Inter- and intra-assay CVs ranged from 2.4{\%} to 5.0{\%} which is within the minimum acceptance criteria based on biologic variation. The reference interval of IGF-I was wide (90–1207 ng/mL) and there was a significant association between body weight and ln IGF-I (P < .000001).ConclusionsThis human ELISA is suitable for feline samples, but interfering IGFBP can cause falsely low concentrations. It is recommended to dilute samples such that IGF-I is < 28 ng/mL on the standard curve to grant for sufficient IGF-II for binding of interferent IGFBP.",
keywords = "growth hormone disorders, insulin-like growth factor-binding proteins, size-exclusion chromatography",
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Insulin-like growth factor-I in cats : validation of an enzyme-linked immunosorbent assay and determination of biological variation. / Strage, Emma M.; Theodorsson, Elvar ; Ström Holst, Bodil ; Lilliehöök, Inger ; Lewitt, Moira.

In: Journal of Veterinary Clinical Pathology, Vol. 44, No. 4, 2015, p. 542-551.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Insulin-like growth factor-I in cats

T2 - validation of an enzyme-linked immunosorbent assay and determination of biological variation

AU - Strage, Emma M.

AU - Theodorsson, Elvar

AU - Ström Holst, Bodil

AU - Lilliehöök, Inger

AU - Lewitt, Moira

PY - 2015

Y1 - 2015

N2 - BackgroundInsulin-like growth factor I (IGF-I) measurements are used in veterinary medicine for diagnosing growth hormone disorders. IGF-I assays are subject to interference by IGF-binding proteins (IGFBP) which may not be efficiently removed by standard extraction methods. Adding excess IGF-II during analysis may improve accuracy.ObjectivesThe purpose of the study was to validate a commercial human IGF-I ELISA which uses excess IGF-II for feline samples and to evaluate biologic variation.MethodsPrecision was determined by calculating the coefficient of variation (CV). Accuracy was determined by recovery after removal of IGFBP, addition of IGF-I, and linear dilution after the addition of IGFBP. Biologic variation was determined by repeated sampling in 7 cats.ResultsThere was interference by IGFBP in the high measuring range, resulting in falsely low IGF-I concentrations. This was overcome by the addition of high concentrations of IGF-II. Untreated serum had a measured/expected ratio of 98–115% compared to serum where IGFBP had been removed. Recovery after the addition of IGF-I was 83–112%. Inter- and intra-assay CVs ranged from 2.4% to 5.0% which is within the minimum acceptance criteria based on biologic variation. The reference interval of IGF-I was wide (90–1207 ng/mL) and there was a significant association between body weight and ln IGF-I (P < .000001).ConclusionsThis human ELISA is suitable for feline samples, but interfering IGFBP can cause falsely low concentrations. It is recommended to dilute samples such that IGF-I is < 28 ng/mL on the standard curve to grant for sufficient IGF-II for binding of interferent IGFBP.

AB - BackgroundInsulin-like growth factor I (IGF-I) measurements are used in veterinary medicine for diagnosing growth hormone disorders. IGF-I assays are subject to interference by IGF-binding proteins (IGFBP) which may not be efficiently removed by standard extraction methods. Adding excess IGF-II during analysis may improve accuracy.ObjectivesThe purpose of the study was to validate a commercial human IGF-I ELISA which uses excess IGF-II for feline samples and to evaluate biologic variation.MethodsPrecision was determined by calculating the coefficient of variation (CV). Accuracy was determined by recovery after removal of IGFBP, addition of IGF-I, and linear dilution after the addition of IGFBP. Biologic variation was determined by repeated sampling in 7 cats.ResultsThere was interference by IGFBP in the high measuring range, resulting in falsely low IGF-I concentrations. This was overcome by the addition of high concentrations of IGF-II. Untreated serum had a measured/expected ratio of 98–115% compared to serum where IGFBP had been removed. Recovery after the addition of IGF-I was 83–112%. Inter- and intra-assay CVs ranged from 2.4% to 5.0% which is within the minimum acceptance criteria based on biologic variation. The reference interval of IGF-I was wide (90–1207 ng/mL) and there was a significant association between body weight and ln IGF-I (P < .000001).ConclusionsThis human ELISA is suitable for feline samples, but interfering IGFBP can cause falsely low concentrations. It is recommended to dilute samples such that IGF-I is < 28 ng/mL on the standard curve to grant for sufficient IGF-II for binding of interferent IGFBP.

KW - growth hormone disorders

KW - insulin-like growth factor-binding proteins

KW - size-exclusion chromatography

U2 - 10.1111/vcp.12289

DO - 10.1111/vcp.12289

M3 - Article

VL - 44

SP - 542

EP - 551

JO - Journal of Veterinary Clinical Pathology

JF - Journal of Veterinary Clinical Pathology

SN - 1939-165X

IS - 4

ER -