Criteria for Identification of Homogeneous Electrophoretic Peaks in Multiple Myeloma †

In 1939, Longsworth, Shedlovsky and MacInnes described the occurrence of abnormal Tiselius electrophoretic patterns in multiple myeloma.' These findings were confirmed by Kekwick,5 Gutman! and Moore' and their coworkers who pointed out that the characteristic pattern showed a sharp, narrow globulin component of variable electrophoretic mobility. During the next decade electrophoretic analyses of serum proteins of patients with myelomatosis were carried out by many investigators.`~In all of these studies the abnormal proteins were characterized simply as "tall, narrow peaks,"' "electrophoretically homogeneous proteins,"7 or "sharply defined peaks."5 Similar abnormal globulins have been demonstrated by filter paper electrophoresis in patients with myelomatosis, and the same terms have been used to describe them.Y' Patterns of this type have generally been considered diagnostic of myelomatosis.5'7"'U Although the classic "myeloma" pattern can be readily recognized by inspection of the stained filter paper strip, some patients with myelomatosis exhibit more subtle, nonspecific abnormalities.5'7'8,10 Often these abnormalities are due to the presence of small amounts of abnormal protein which are barely discernible against the background of the normal protein components and do not satisfy the criteria of dense, narrow, sharply defined bands. Furthermore, recent studies have shown that other disorders may exhibit abnormal electrophoretic patterns that appear to be indistinguishable from those of multiple myeloma.'-" Several authors have suggested objective criteria for the identification of homogeneous myeloma peaks. Harboe found that the width of such peaks measured at a point two thirds of the distance from the base to the apex