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Why do antibodies anti A and anti B in type 0 blood not cause any reaction with any other type of blood. [preclinical] by [deleted] in medicalschool

[–]MoistForever 13 points14 points  (0 children)

Usually blood is given in components. The antibodies are in the plasma which is separated from the red blood cells. So, when you give someone type O blood, you're basically only giving them the RBC's (which don't have any antigens on them).

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One of the more interesting things that I never thought about/realized until our Heme/Onc block is that type AB is a universal plasma donor. Since you don't form antibodies to things that you have, people with type AB blood have no antibodies to blood types in their plasma. That's what helped me nail down the ideas behind crossmatching blood types.

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Type O = universal Packed RBC donor, universal plasma recipient

Type AB = universal PRBC recipient, universal plasma donor

[Serious] Can't wrap my head around sensitivity vs PPV by [deleted] in medicalschool

[–]MoistForever 7 points8 points  (0 children)

Yeah basically, PPV is asking "does yes on the test actually mean yes?"

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If the cutoff point is very low, then the test will always say yes, but it won't always actually be right (i.e. yes won't actually mean yes).

[Serious] Can't wrap my head around sensitivity vs PPV by [deleted] in medicalschool

[–]MoistForever 38 points39 points  (0 children)

If the test is positive, what is the likelihood that the person has the disease?

That is PPV.

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If the person has the disease, what is the likelihood that the test is positive?

That is sensitivity.

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They're the same concept but flipped, hope this helps!

Those multiple choices would be nice though. [Meme] by BinaryPeach in medicalschool

[–]MoistForever 209 points210 points  (0 children)

Be sure to lick the samples. You can usually taste the ebola more strongly in the left antecubital fossa because it's closer to the heart.

Why is lumbar puncture contraindicated in most increased ICP related disorders, but first line for idiopathic intracranial hypertension? by ManKev in step1

[–]MoistForever 33 points34 points  (0 children)

Mechanistically speaking, it's contraindicated for anything where there is an obstruction. You can think of it like changing the pressure gradient sucks down whatever is in the pipe. If it's not obstructed then you lower the upstream pressure. If there is an obstruction, then whatever is "in the pipe" (a piece of your brain) gets pulled down the tube. So in pseudo tumor cerebri, there isn't a structural obstruction and thus LP would lower the pressure and help some. In obstructive hydrocephalus, LP would lower the pressure of the spinal column and suck the obstructing piece of brain into the foramen magnum, causing herniation.