Re Glucose Tolerance Test with Concurrent Insulin levels.
>
> There are two important points which I should mention when testing insulin
> levels. Firstly, your doctor could order a single fasting glucose+
> fasting insulin & also glucose+insulin levels one hour after completion of a
> main meal, before ordering the full glucose tolerance test; especially
> those who are worried about the possible ill effects of a glass of glucose.
> Secondly, the kit used in the insulin assay at the lab. where my tests are
> done is the :-
> Phadeseph Insulin RIA Radioimmunoassay from Pharmacia.
> In my experience transport of specimens should only be done if the
> specimen of serum is
> frozen in dry-ice (ie carbon dioxide ice or snow) Serum remains liquid
> in water ice; there is a need to
> standardise protocols for transport of serum for insulin assay; in the mean
> time, the results are so valuable, why jeopardise the result for the sake of
> a little incovenience!
> The correct protocol for Insulin Assay includes
> 1. Collection of blood into a "Plain Top" bottle and blood allowed to clot.
> 2. Specimen is centrifuged and the serum separated and serum frozen
> within 30 minutes of collection at -20degrees C.
> 3. If specimen is to be transported, it should only be carried in an
> insulated box containing dry ice(ie frozen carbon dioxide); this is
> a much lower temperature than water ice. It must not be
> transported in an ice box with water ice; this is at 0 degrees C &
> the serum remains fluid; the slopping about of the liquid serum
> may account for inaccuracies which have been documented in
> insulin assays.
> Allen E Gale. 27 9 96

 

INSULIN ASSAY

The assay of serum for insulin levels requires critical laboratory handling procedures. See information below on this page and also in the links below.

But the performance of insulin assays concurrently with an Oral Glucose Tolerance Test (OGTT) provides information on the ability of the pancreas to respond to the entry of glucose to the blood stream. This response in any individual is governed by many factors; eg i)heredity, ii)intra-uterine hormonal environment before the individual's birth, iii)as a neonate the insulin levels in the mother's breast milk*, iv)diet, v)exercise, vi)body mass with feedback from PC-1 produced in the intra-abdominal fat, vii)endocrine changes associated with puberty, menstruation, pregnancy, menopause, vii)endocrine changes associated with stress of any kind, whether physical or surgical trauma, infection or emotion.

Until the doctor understands the above, he should not venture to comment on the value of insulin assays!!!!!

References to substantiate the above will be found if you search my numerous pages on the www. Experimental work to support the buccal absorption of insulin in the breast* fed infant is awaiting publication. I will add those references as time permits. Dr Allen E Gale Consultant Physician & Adelaide Aerobiology Laboratory, South Australia 0620hours October 11, 2000

 

Explaining the importance of correct handling procedures for insulin assays to laboratories who have strict budget constraints has proved a sisyphean task! Now that there is accelerating interest in insulin assays, I reproduce correspondence from the manufacturer forthwith:-

Subject: Insulin Storage Conditions

Date: Wed, 30 Jul 1997 19:36:23 -0500

Dr Gale

I am the Product Manager for Immunodiagnostics at Abbott which includes our Insulin assay. FW* has forwarded to me your E-Mail with your concerns at the apparent poor storage conditions of Insulin specimens . The case studies you included certainly highlight the importance of laboratories maintaining strict storage and transport conditions.

I would like to point out that in our package insert there is considerable attention given to the storage conditions of Insulin specimens. Of most relevance are the points " All specimens should be stored at -20C or colder" and "The freeze thaw cycles should be avoided". This would seem to concur with your considerable first hand experience on this matter. I am not able to say whether the other suppliers of Insulin reagents have the same instructions.

I will be sending our Insulin Package Insert to you for your records. This key point has been noted and communications with our customer base will be initiated informing them of the importance of maintaining correct and stated storage conditions for Insulin specimens as per our Package Insert instructions . I will also be forwarding to you this notice.

Dr Gale, I appreciate your concern and you drawing to our attention this deficiency in laboratory Quality Control procedures. Abbott is committed to pursuing the strict adherence of our Package Insert instructions and please do not hesitate in contacting me on this or any matter that Abbott Diagnostics may be able to assist.

Yours sincerely

PG*

Product Manager- Immunodiagnostics

*Names on file