Filter Paper Blood Spot Assay of Human Insulin-Like Growth Factor I (IGF-I) and IGF-Binding Protein-3 and Preliminary Application in the Evaluation of Growth Hormone Status
Anastasia Diamandi,
M. Javad Khosravi,
Jehangir Mistry,
Victor Martinez and
Jaime Guevara-Aguirre
Diagnostic Systems Laboratories (Canada), Inc. (A.D., M.J.K.), and
the Department of Laboratory Medicine and Pathobiology, Faculty of
Medicine, University of Toronto (M.J.K.), Toronto, Ontario, Canada;
Diagnostic Systems Laboratories, Inc. (J.M.), Webster, Texas 77598; and
the Institute of Endocrinology, Metabolism, and Reproduction (V.M.,
J.G.-A.), Quito, Ecuador
Address all correspondence and requests for reprints to: M. J. Khosravi, Ph.D., Diagnostic Systems Laboratories (Canada), Inc., Mount Sinai Hospital, Room 653, 600 University Avenue, Toronto, Ontario, Canada M5G 1X5.
To facilitate broader applications of insulin-like growth factorI
(IGF-I) and IGF-binding protein-3 (IGFBP-3) analysis, we developed
proceduresfor their measurements in extracts of whole blood dried on
filterpaper. A single 8-mm diameter filter paper disc containing about
13µL blood was used. IGFBP-3 was efficiently extracted ina buffer
within 1 h of incubation. IGF-I extraction involvedincubation in
buffer followed by acidification and neutralizationsteps. Blood spot
assays showed intra- and interassay coefficientsof variation
(including interspot variations) of 5.4–16.7%for IGF-I and
6.6–11.7% for IGFBP-3; recoveries were 97± 7.1% and 101
± 8.7%, respectively. Recoveriesof IGF-I and IGFBP-3 in response to
4- to 8-fold variationsin extraction buffer volume were 97 ±
8.2% and 107 ±6.1%, respectively. Dried blood spot IGF-I and
IGFBP-3 showedgreater than 1-month stability at -20 C, 4 C, and room
temperatureand retained more than 65% of the immunoreactivity after
approximately1 month at 37 C. Both IGF-I and IGFBP-3 were contained
withinthe plasma fraction of whole blood, and variations (mean ±
SD)in IGF-I (204 ± 29 µg/L) and IGFBP-3 (4.4
±0.48 mg/L) measured in extracts of dried blood spot with adjusted
hematocritof 0.2–0.62 were acceptable. IGF-I and IGFBP-3 in paired
plasmaand dried blood spot extracts of random samples (n = 46)
showedexcellent correlation (r > 0.94) with slopes of near
unity.Compared to conventional methods, the filter paper procedures
wereequally effective in distinguishing IGF-I and IGFBP-3 levelsin
untreated GH receptor-deficient (n = 11) and age-matchednormal
controls (n = 16). We conclude that blood collected onfilter
paper is ideal for IGF-I and IGFBP-3 analysis and mayfind applications
in pediatric and large scale infant screeningprograms.
This article has been cited by other articles:
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[Abstract][Full Text]
M. L. Mitchell and Hermos; Comment on Dried Blood Spot Assay of IGF-I and IGFBP-3
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84(2):
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[Full Text]
J. Khosravi and A. Diamandi Dried Blood Spot Assay of Insulin-Like Growth Factor (IGF)-I and IGF Binding Protein-3 (IGFBP-3)--Authors' Response
J. Clin. Endocrinol. Metab.,
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[Full Text]
