Question: Hey Kym, i am very interested in your involvement in testing blood for diseases, my question for you is, when a man or woman is showing early signs of cancer such as Pruritus and it is constant for months and they decide to go to the doctor and they get their blood checked, once the blood is given to you, how do you find the cancer or disease? and also Once you have found it how do you know which treatment is suitable?

Excellent question! Using your example, there are lots of different causes for pruritis, including diabetes, allergies, iron deficiency anaemia, jaudice (liver problems), thyroid problems, uraemia (kidney problems) and some cancers like lymphoma and Hodgkins disease. If someone went to their doctor complaining of this their doctor would send them along to us for some screening blood tests. These would probably include:
– Full blood (FBC)
– Liver function test (LFT)
– Urea, creatinine & electrolytes(UEC) kidney function test
– blood glucose level
– Thyroid stimulating hormone (TSH) level
– RAST test

Thats great I can hear you say – but what do all those things mean?? I’ll do the easy ones first, and leave the big one until last. The LFT and UEC are groups of biochemical tests that we can do to check how healthy a person’s liver and kidney are. If a person is jaundiced the bilirubin level in the LFT will be elevated – and you would be able to see this without even doing a blood test, their skin would have a yellow tinge, and the whites of their eyes would be yellow. An excess of bilirubin irritates the skin at very high concentrations, like you see in jaundice and will cause pruritis. If this is the cause the doctor will probably order more tests on the liver, such as an ultrasound or CT scan to check for things like gall stones or even a tumour to see what is causing the jaundice. Another cause of pruritis I mentioned was uraemia, which is an excess of urea in your system. This will be seen in the UEC (thats what the U stands for!). Urea is normally excreted by the body as part of your urine, but if your kidneys aren’t working properly it can build up – and sometimes the first sign that something is wrong is itchy skin.

Blood glucose level and TSH are pretty straight forward, we measure the levels of those two things. Very occasionally diabetes can cause itchy skin, and a glucose level is something that can easily be checked so while we have a blood sample a doctor will often check it. Your thyroid gland is a very important gland found in your neck that plays an important part in metabolism and how your body reacts to other proteins (its really really complicated!). If the TSH level is out of whack all sorts of things can be affected, and one possible symptom is pruritis.

A RAST test is a specialised allergy test (which is short for radioallergosorbent test!) where we can determine specifically what a person is allergic to. In the case of someone going to a doctor with pruritis they might order a screening RAST to groups of the most common allergens – food mixes (nuts, seafood, dairy), grass mix (a mix of 4 common grass pollens), tree mix (4 common tree pollens) and dustmite. If the doctor suspects something in particular might be causing an allergic reaction (for example maybe the itchyness started when the patient’s family got a new pet cat) they can ask for a specific RAST (eg cat RAST).

And now for the FBC. This test can tell us a lot about a patient – it will tell us their haemoglobin level (how well their blood can transport oxygen around the body), how many red blood cells they have and the size (this is important), how many white blood cells there are and what type and how many platelets. In the example you’ve given me we would be especially interested in the white blood cells (WBC) and what sort they are. There are 5 main type that we can get our machine to count, or we can count as a percentage by looking at a stained blood film under a microscope. They are neutrophils, lymphocytes, monocytes, eosinophils and basophils. If the total number of WBC is increased it can mean there is an infection of some sort if it is only mildy increased, or if it is off the charts, HUGELY high that can indicate a form of cancer. In an adult a WBC should be somewhere between 4 – 11 x 10^9 cells/L. If someone had leukaemia (blood cancer) it wouldn’t be unusual to see the WBC at 50 x10^9 cells/L or higher. And when we look at the blood film (https://www.idexx.com/pubwebresources/images/en_us/smallanimal/diagnosticedge/december2010/1210_04.png this is the sort of thing we see down a microscope) we can tell by the shape of the WBC whether they are mature (which is what we want to see in someones blood) or what we call blast cells, which should only be found in your bone marrow. Someone with an acute leukaemia will often have greater than 20% of the WBC on their blood film that we look at are actually blast cells.

So you can see, its all very complicated! What happens is I look at the results, and if I have been told the history of the patient by the doctor I might be able to give an interpretation of the results I’m seeing for them on the report I send back (but often doctors don’t tell us the clinical history which makes it hard!!). Once the doctor has the results back it is up to them to decide which is the most suitable treatment for the patient – they know everything about the patient, all their medications and their history so can safely choose the best option. S a medical laboratory scientist I am always here for the doctors to ask questions about results, and I can offer advice about the best tests to do to find out the answers they need so they can decide what is best for their patients.