LP...what are bloods for?

Hi everyone

i had an LP last week and though seem to (so far) have escaped side effects and the headaches wondered why they took bloods as I thought no blood test could confirm /support an MS diagnosis? My neuro has only mentioned MS re my MRI results so not sure if bloods was a hospital box checking or really required.



The LP is to take cerebral spinal fluid, not blood. They look for antibodies/proteins in the fluid. If they are present then it confirms the presence of your body fighting an infection in your nervous system. This is because MS is an auto-immune disease where your own antibodies attack your own system and demeyelinate the covering causing plaques/lesions.

I think anyways, I just got diagnosed a few weeks ago but that is my understanding of it. Apologies if I am wrong.

Hi Chris,

They take bloods at the same time because they check to see whether you have obands in the CSF and blood. If the obands are present in both it means general inflammation. To be positive for MS you need obands in the CSF which aren’t present in the blood.This tells them the inflammation is only in the central nervous system. That’s my understanding anyway.

Snowqueen x

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Thanks a lot snow queen makes good sense. assume no o bands in CSF but present in blood means the general/other inflammation thing?

Snowqueen is quite right - bloods are always taken at the same time as the CSF sample, as what matters is a comparison of the two.

But irrespective of that, it is normal to have blood tests as part of an investigation for MS, even if you don’t have an LP, because they’re not just looking for MS, but anything else it might be. MS doesn’t show in the blood, but some of the other possibilities do, so they could not say confidently that you have MS without screening for the other stuff.


Not sure about relevance of serum but not CSF. O Bands are not exclusive to MS and can be present in other CNS conditions too. If you look up the Macdonald Criteria you will see the LP results are used alongside other things to confirm diagnosis. MRI and Clinical findings also form part of this.

Snowqueen x

I don’t think it’s of any clinical significance to have “a few” (two or three?) o-bands in the blood ONLY.

The key findings would be matching O-bands in blood AND CSF (indicative of systemic inflammation) OR o-bands in CSF NOT matched in blood - indicative of inflammation specific to the CNS.

I think a couple of o-bands in blood but nowhere else is pretty much fine.

I haven’t Googled to double-check this, so just going from memory (not always a good idea).


I didn’t have blood drawn when I had an LP o.o I wasn’t aware that should have happened, I wonder why they didn’t. I’m quite confused now.