The effects of a freeze-thaw cycle and pre-analytical storage temperature on the stability of insulin-like growth factor-I and pro-collagen type III N-terminal propeptide concentrations: Implications for the detection of growth hormone misuse in athletes

TY - JOUR

T1 - The effects of a freeze-thaw cycle and pre-analytical storage temperature on the stability of insulin-like growth factor-I and pro-collagen type III N-terminal propeptide concentrations: Implications for the detection of growth hormone misuse in athletes

AU - Guha, Nishan

AU - Erotokritou-Mulligan, Ioulietta

AU - Bartlett, Christiaan

AU - Cowan, David A.

AU - Bassett, E. Eryl

AU - Stow, Michael

AU - Soenksen, Peter H.

AU - Holt, Richard I. G.

PY - 2012/6

Y1 - 2012/6

N2 - A method based on two serum biomarkers insulin-like growth factor-I (IGF-I) and pro-collagen type III N-terminal propeptide (P-III-NP) has been devised to detect growth hormone (GH) misuse. The aims of this study were to determine the stability of IGF-I and P-III-NP concentrations in serum stored at -20 degrees C and to establish the effects of one freeze-thaw cycle. Blood was collected from 20 healthy volunteers. Serum aliquots were analyzed after storage for one day at 4 degrees C and one day, one week, five weeks, and three months at -20 degrees C. IGF-I and P-III-NP results were combined to calculate a GH-2000 discriminant function score for each volunteer. Inter-assay precision was determined by analysing one quality control sample at each time-point. A single freeze-thaw cycle, storage of serum at 4 degrees C for one day and at -20 degrees C for up to three months had no significant effect on IGF-I or P-III-NP concentration. Intra-sample variability for IGF-I was 6.8% (Immunotech assay) and 12.9% (DSL assay). Intra-sample variability for P-III-NP was 10.9% (Cisbio assay) and 13.7% (Orion assay). When IGF-I and P-III-NP results were combined, intra-sample variability of the GH-2000 score expressed as a standard deviation varied between 0.31 and 0.50 depending on the assay combination used. Variability in IGF-I and P--III-NP results of stored samples is largely determined by the characteristics of the assays. A single freeze-thaw cycle, storage of serum at 4 degrees C for one day or at -20 degrees C for up to 3 months does not result in a significant change in GH-2000 score. Copyright (C) 2012 John Wiley & Sons, Ltd.

AB - A method based on two serum biomarkers insulin-like growth factor-I (IGF-I) and pro-collagen type III N-terminal propeptide (P-III-NP) has been devised to detect growth hormone (GH) misuse. The aims of this study were to determine the stability of IGF-I and P-III-NP concentrations in serum stored at -20 degrees C and to establish the effects of one freeze-thaw cycle. Blood was collected from 20 healthy volunteers. Serum aliquots were analyzed after storage for one day at 4 degrees C and one day, one week, five weeks, and three months at -20 degrees C. IGF-I and P-III-NP results were combined to calculate a GH-2000 discriminant function score for each volunteer. Inter-assay precision was determined by analysing one quality control sample at each time-point. A single freeze-thaw cycle, storage of serum at 4 degrees C for one day and at -20 degrees C for up to three months had no significant effect on IGF-I or P-III-NP concentration. Intra-sample variability for IGF-I was 6.8% (Immunotech assay) and 12.9% (DSL assay). Intra-sample variability for P-III-NP was 10.9% (Cisbio assay) and 13.7% (Orion assay). When IGF-I and P-III-NP results were combined, intra-sample variability of the GH-2000 score expressed as a standard deviation varied between 0.31 and 0.50 depending on the assay combination used. Variability in IGF-I and P--III-NP results of stored samples is largely determined by the characteristics of the assays. A single freeze-thaw cycle, storage of serum at 4 degrees C for one day or at -20 degrees C for up to 3 months does not result in a significant change in GH-2000 score. Copyright (C) 2012 John Wiley & Sons, Ltd.

KW - GH-abuse

KW - IGF-I

KW - P-III-NP

KW - pre-analytical factors

KW - doping

KW - BINDING PROTEIN-3

KW - ABUSE

KW - SPORT

KW - PEPTIDE

U2 - 10.1002/dta.1339

DO - 10.1002/dta.1339

M3 - Article

SN - 1942-7603

VL - 4

SP - 455

EP - 459

JO - Drug Testing And Analysis

JF - Drug Testing And Analysis

IS - 6

ER -