HOW THE PAST MAY BRING THE FUTURE TO DISEASE DIAGNOSIS
“ Taking a child for a blood test is one of the most ”
stressful experiences both a parent and child can undergo.
or some change in electromagnetic spectrum from a sample. The methods of how this is achieved range from simple enzyme catalyzed reactions to sophisticated immunoassay experiments, but all using light to detected changes. Plasma is key for these assays because it can allow light to penetrate it. Blood, being the colour that this is, is incompatible with many of these assays. Furthermore, instrument manufacturers will often declare a maximum percentage allowable hemolysis.
Other reasons why plasma is chosen over blood is that plasma is seen as a simpler matrix to measure analytes. Another argument for plasma is based on what is more physiologically relevant, blood or plasma? And there are compelling arguments for both sides. Nevertheless, with the emergence of newer technologies like LC–MS and some immunoassays, assays developed from blood are indeed possible. So, blood does offer some distinct advantages.
6 AN ARGUMENT FOR BLOOD
Taking a child for a blood test is one of the most stressful experiences both a parent and child can undergo. Moreover, the smaller the child the less free circulating blood. Blood volumes are dependent on the age and size of the individual. An average 70-kg adult will have approximately 5 l of blood, which is plenty for standard blood tests where vacutainers hold up to 10 ml of blood per tube. However, a neonate weighing 3 kg will only have approximately 250 ml of blood. So specialized blood tubes are needed to collect small volumes of blood (1 ml).
Care needs to be taken about the total allowable amount of blood that can be taken from an individual. There are various guidelines in the literature for what this limit is. Let’s take 5% total blood taken per 30-day period as an example; this is only about 12 ml for a 3-kg neonate! This is a lot of blood, especially if regular blood draws are needed. Due to this, the smaller the blood samples the better for the patient. However, harvesting good-quality plasma as a microsample is possible but poses technical and practical challenges. Analyzing whole blood samples solves this issue; however analyzing whole blood microsamples on clinical chemistry analyzers also poses huge technical challenges. There must be a better way to conduct blood tests, and the answer could come from the emergence of the omics revolution.
IS MICROSAMPLING AND OMICS THE ANSWER?
Omics is a broad term for the emerging science of global screening. Omics is all about finding the proverbial needle in the haystack, whether the haystack is the proteome, genome or metabolome. Omics require very sensitive instruments with high levels of selectivity. The sensitivity of some of these instruments is allowing some labs to employ microsamples in their very promising research.
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