Imagine you want to know how much iron, HGC or cholesterol you have in your blood, what does people look at? I try to search on internet and fail to find. I naively imagined it would be with a microscope but also… it feels weird and would ask to like… count manually?
Just wondering how they do…
In: Biology
There are a ton of different ways, some more efficient and specific, some cheaper, and they change depending on what you are looking for.
Overall most of the methods measure the quantity indirectly, seeing how something interacts with the substance being measured, and then quantifying that interaction.
For example, for cholesterol a common method is using a molecole that emits light when binding cholesterol, so they add it to the blood and then measure how much light is being emitted with high precision instruments.
I’m pretty sure all of the listed blood tests are done using different analytical methods (different ways to prepare the sample before finally running it on an instrument). I am pretty sure they don’t use a microscope for most blood tests. They use chemistry to prepare the blood sample, which then gets analyzed by an instrument to produce a quantitative result.
Below is a link to a pdf of the procedure for iron analysis.
https://www.cdc.gov/nchs/data/nhanes/nhanes_01_02/l40fe_b_met_iron_tibc_alpkem.pdf
It depends on what you’re testing for.
For many tests, you add one or more chemicals to a sample of blood to react with the thing you’re testing for, and then quantitatively measure some result of the reaction.
For example, in the [CDC’s documented procedure for measuring serum iron](https://www.cdc.gov/nchs/data/nhanes/nhanes_01_02/l40fe_b_met_iron_tibc_alpkem.pdf) a chemical called ferrozine is added to a small amount of blood. Ferrozine reacts with the iron in blood to form a compound that is purple. The intensity of the purple color is directly proportional to the amount of iron-ferrozine complex, and so to the amount of iron in the sample. You measure the intensity of color by using a piece of lab equipment called a colorimeter.
For other things, you _can_ literally count them. Take a drop of blood, put it on a microscope slide, and count say the number of white blood cells you see per square millimeter. Count a bunch of square millimeters, average out the count, then scale it up from the volume of one square millimeter of blood in a microscope slide to something standard like a milliliter.
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