Hi ans welcome,
In normally functioning kidneys, the level of creatinine in the urine compared to the blood, should be high as it is being passed out efficiently, so if it's abnormally low it could be an indication of a kidney related condition going on...blood test results have no connection with MS so it's possible for this test results to be pointing away from neurological conditions like MS and get you having more associated testing done.
Hope that helps.......JJ