UMHB: Chapter 1 - 2 doubts on blood test (1)

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In-range red blood cell count meaning no anemia?

A lot of people went for blood test. Blood test is usually conducted by taking certain amount of blood from a human body, keep in a tube, then send it to lab for different kind of assay. Some common tests are red blood cell count (RBCC), white blood cell count and platelet count. If RBCC is less, doctor will usually say you have anemia. If excess in white blood cell count, the claim will maybe is inflammation, or even leukemia.

These scientific tests looks convinced, and seems fine for all these while. But if you think about it deeply, it might not be the actual story. Let's take the example of RBCC and anemia. Anemia means the total blood volume in someone body is not sufficient. Are you convinced that just a few tenth or hundred CC of blood that a blood test can measure your total blood volume? In brief, blood test assay is taking proportion of certain substance inside a certain volume of blood, which is quantitative measurement. It doesn't sounds logic that we can measure total blood volume inside a body using this kind of quantitative measurement. Let me describe using a real life example. Assume inside a mall there are 1 million people and we do not know. We would like to know the total number of people and we started the survey. If we sample using 100 people, 60 men and 40 women, we may be able to get the proportion of man to woman in the mall, but we will never able to know the total number of people inside the mall! Thus it doesn't sounds logic we can tell someone is having anemia simply from a few tenth/hundred cc blood test.

Total value of red blood cell count should be red blood cell concentration level multiply total volume of blood. If we assume red blood cell concentration level is RBCC, then it is assuming the total volume of blood is always a constant. But in real, there is no proof that total volume of blood is always a constant. Logically total volume of blood always changed. Let's discuss further. In blood, big portion is serum, where serum comprises of water mostly. So if RBCC is low, it could means that serum is high, and vice versa. But it doesn't means that the total volume of RBCC is at adequate level.

These type of tests usually has no big impact on normal people, it is not danger. But in emergency room, these readings sometimes decided a patient's chances of live or die. These blood figure are used to determine if blood transfusion is needed, but sometimes maybe the patient body cannot absorb water well which make the RBCC value is in-range. But in fact he need bloods but was fooled by the 'normal' RBCC reading. The risk is he lost his life of not getting adequate blood transfusion.

Blood test is the simplest test, if it itself is not convinced, how convinced we are with other type of test?