Bio-Rad Human Metabolic and Hormone Assays - Manual (Page 16)

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5. Prepare Samples
Note: Most of the circulating IGF-1 and IGF-2 are complexed with the
IGFBPs. An extraction step to separate the complexes is required prior
to measuring the IGFs in serum and plasma samples. Users measuring
free IGF should skip the sample extraction step and proceed to dilute
the sample 1:5 with the provided sample dilution buffer. Thaw and dilute
samples within 1 hr of use. Remove any particulates by centrifugation or
filtration. Avoid multiple freeze and thaw cycles.
The kit has sufficient reagents to run 37 samples in duplicate for a full plate
analysis. General guidelines for preparing samples are provided below. For
more information, contact Bio-Rad Technical Support.
Serum and Plasma
Serum, EDTA plasma, or citrate plasma are the preferred sample types for
these assays. Heparin-treated plasma, while compatible with these assays,
may absorb certain soluble proteins of interest.
Note: Plasma is preferred for detection of IGFBP-5, as levels may be below
detection in serum.
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Avoid using hemolyzed samples, as this may lead to false results.
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Freezing samples at –70°C immediately after preparation and keeping
samples frozen until use should provide adequate protection from
degradation. Avoid multiple freeze and thaw cycles.
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Once thawed, keep samples on ice.
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Do not freeze diluted samples