I don't know if this will answer your question or not, but I found a labaratory link:
What about the O-band test?
Is this the initial report? So it doesn't include the O-bands yet?
Well, I'm not versed in this very well at all, but my thoughts are that low IgG would mean a deficiency when they drew the serum. Sometimes they choose to run the lab again, recheck your serum when this happens. But this particular serum will be compared against the CSF for LP results. So it might be something your Dr. will run again to see if it comes up low again.
I'm not so sure if deficient IgG in your serum in and of itself says much at this time for you unless they ran some other test on your blood serum or plan to run tests based on this result. i.e., for infections, etc. Look at you clinically to see what could be the cause.
I'm probably not the right person to be responding this one, but just don't want you to be worried while you wait. How are you feeling? Have you been sick at all?
I hope it's just a fluke.
Please friends, correct anything I've messed up here.... just going off of some info I received when I went to the hematologist and hoping I'm remembering correctly.
My favorite labsite to check this out is
labtestestsonline - it is an org - trying to out smart thatdarn website censor her. when I put in lumbar puncture, here is what I get about some of the things they look at in our csf samples -------
CSF protein electrophoresis — separates different types of protein. Oligoclonal bands may be seen with multiple sclerosis and Lyme disease.
CSF IgG (Immunoglobulin G) — increased in some conditions, such as multiple sclerosis, herpes encephalitis, connective tissue diseases.
Myelin basic protein — seen when the covering of nerves (myelin) breaks down, such as with multiple sclerosis.
CSF lactic acid — often used to distinguish between viral and bacterial meningitis. The level will usually be increased with bacterial and fungal meningitis while it will remain normal or only slightly elevated with viral meningitis.
CSF lactate dehydrogenase (LD) — used to differentiate between bacterial and viral meningitis; may also be elevated with leukemia or stroke.
CSF glutamine — may be increased with liver disease: hepatic encephalopathy and Reye syndrome
CSF C-reactive protein (CRP) is an acute phase reactant and is elevated with inflammation. It is markedly increased with bacterial meningitis. Since it is very sensitive even with early bacterial meningitis, it is often used to distinguish between bacterial and viral meningitis.
Tumor markers — Carcinoembryonic antigen (CEA), alpha-fetoprotein (AFP), and hCG may be increased in cancers that have spread from other sites in the body (metastatic).