In the
rheumatic diseases, the changes in the
carbohydrate part of serum
glycoproteins occur and these abnormalities can be monitored by serum level of total and free
sialic acid. The aim of this study was to evaluate the total and free
sialic acid level as a marker of
inflammation activity (
TSA) and the changes in glycosylation of blood
glycoproteins (FSA) in
rheumatoid arthritis (RA),
systemic sclerosis (SSc) and
systemic lupus erythematosus (SLE). Studies were carried out in 50 patients with RA, 24 with SLE and 32 with SSc.
TSA concentration was measured with an enzymatic, colorimetric method and FSA with a thiobarbituric method. The serum levels of
TSA in RA and SLE patients were significantly increased compared to controls and in RA patients were higher than that in SSc patients. The mean serum level of FSA in RA patients was significantly higher, but in SSc patients significantly lower than that in the controls, and in RA patients was significantly higher than in SLE and in SSc patients. All
acute-phase proteins were changed: Positive
acute-phase proteins were elevated, and the negative
protein was decreased. The positive
acute-phase proteins positively correlated with the levels of
TSA and FSA in RA and SSc patients. In SLE patients,
TSA positively correlated with
haptoglobin and α1-antitrypsin. In RA patients, there was the positive correlation of
TSA and FSA with
DAS 28. The changes in the serum levels of
TSA and FSA in the course of
rheumatic diseases could reflect the abnormalities in glycosylation/sialylation patterns of
glycoproteins induced by
acute-phase response.