[Alpha-1-acid glycoprotein in differential diagnosis of rheumatic diseases]

In recent years, the investigation of acute-phase proteins with the aid of affinity electrophoresis employing lectins as carrier substance, has become ever more important, in particular in the diagnosis of inflammatory rheumatic diseases. In order to investigate the usefulness of a determination of alpha-1 glycoprotein microheterogeneity in the sera as a diagnostic parameter, we evaluated, on a prospective basis, the sera of 85 consecutive patients presenting at our department with various inflammatory rheumatic diseases (chronic rheumatoid arthritis [RA] [n = 22], seronegative spondarthropathies [SpA] [n = 15], polymyalgia rheumatica [PMR] [n = 10], polymyositis dermatomyositis [PM/DM] [n = 8], osteoarthritis [n = 18], and infectious diseases [n = 12]). The results were expressed as reactivity coefficient of the alpha-1 acid glycoproteins (AGP/RC). A significant increase in the AGP/RC was observed in patients with various infections, and in those with RA or SpA with intercurrent infection, as compared with patients with RA or SpA with no intercurrent infection, or in healthy controls. It also proved possible to differentiate between PM/DM and PMR. Determination of the erythrocyte sedimentation rate, and quantification of the C-reactive protein and of alpha-1 glycoprotein, permitted no discrimination between an increase in inflammatory activity related to the basic disease, and an intercurrent bacterial infection. The results show that the determination of qualitative changes in the acute phase proteins, in particular alpha-1 acid glycoproteins, may make it possible to differentiate between inflammatory and infectious diseases. This examination technique may be of future clinical importance.