Multiple sclerosis and blood transfusion.

It has recently been suggested that multiple sclerosis (MS) may be triggered by a retrovirally encoded superantigen. If true, then MS should be associated with risk factors that predispose to retroviral infection. Blood transfusions represent one such risk factor. 150 Scottish patients with 'clinically definite' or 'probable' MS and 150 age-/sex-matched neurological controls were questioned about blood transfusion. 7 (4.7%) of the patients and an equal number of controls had received a blood transfusion before the year of disease onset in the matched case (odds ratio 1.0, 95% C.I. 0.3-3.34). These results provide no evidence that blood transfusion is associated with an increased risk of MS.