[Blood group isoagglutinins and immunoglobulins (IgG, IgM) in old age].

Titres of blood-group isoagglutinins and the serum concentration of immunoglobulins M and G were investigated in 388 inmates (89.7% females) of an old-age home, ranging in age from 78 to 99 years [mean (+/- s) = 85.7 years +/- 4.1 years]. Concentrations of isoagglutinins were positively correlated to the concentrations of IgM (total concentration of IgM corr. to IgM anti-B (group A): p less than 0.0005, corr. to IgM anti-A (group B): p less than 0.01, corr. to IgM anti-B (group 0): p less than 0.025), but not to the concentration of IgG. The blood group A IgG red cell alloantibodies (IgG anti-B) indicated, in the low titre range, a positive correlation (p = 0.025) to the IgM isohaemagglutinins (IgM anti-B); the red cell alloantibodies (IgG, IgM) of the other blood groups did not correlate in this way. There was no age-dependent reduction or increase in isohaemagglutinin titres and/or total immunoglobulin levels. From these date we conclude that the lack of red cell alloantibodies in the serum of elderly patients in case of routine ABO blood grouping should not be accepted any more. There has to be an internal diagnosis available or, if missing, coinciding diagnostic tests should be performed.