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Lab Report On Insulin

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Introduction
Insulin is a peptide hormone secreted by the β-cells of the pancreas. It is secreted in response to glucose and secretion occurs in a biphasic pattern. Insulin testing is commonly indicated in the investigation of insulinomas, hypoglycaemia, diabetes, polycystic ovary syndrome, as well as a number of other conditions. The analysis of insulin is often restricted by strict pre-analytical recommendations.
The Chemical Pathology Laboratory at Groote Schuur Hospital Laboratory receives blood samples from a number of external hospitals and laboratories for insulin analysis. Not all samples can be analysed immediately and some may not even be centrifuged before being transported under varying conditions. Whether these samples are still
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Results appear to vary significantly depending on the method of investigation. Differences in the pre-analytical conditions under which insulin is stable seem to follow the use of different collection tubes, assays, temperatures and performance limits. One contradiction seen in the literature is that most studies show decreased stability of insulin at room temperature compared to 4°C, but a contradictory study showed insulin to be stable for the same duration of time at both these temperatures. With the use of different performance limits and room temperature values, such differences are expected. This makes it difficult to apply the results of studies previously conducted to the testing in our laboratory. A similar study of the stability of 81 analytes included insulin and utilised the same analyser, assay type and tube type for their investigation. The results of this study showed insulin to be stable for 72 hours in both whole blood and serum samples at 4°C. Samples (whole blood and serum) stored at 25°C were only stable for 6 hours. The difference in the value of room temperature used (25°C vs. 20.6°C) impair comparability these results to our study. The performance limits used where also…show more content…
Volunteers were selected to meet the criteria of being apparently healthy non-diabetics, but were otherwise selected at random. Volunteers included both male and female adults. Ethics approval was obtained from the UCT Faculty of Health Sciences, Human Research Ethics Committee (Reference number: 383/2015). Collection, storage and analysis of all blood samples was conducted in the Chemical Pathology Laboratory at Groote Schuur Hospital Laboratory. From each volunteer, 6 blood samples were taken (5ml each) and collected into BD SST™ II tubes (gel tubes). BD SST ™ II tubes were chosen as they are commonly used tubes in South Africa for blood collection. 3 of the 6 sample tubes were collected from each volunteer after fasting for 10 hours and 3 sample tubes were collected one hour after ingesting 75g glucose dissolved in water (post-prandial). The sample types were therefore fasting and
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