Value of serum IgG4 in diagnosis of IgG4-related disease and in differentiation from rheumatic diseases / 中华检验医学杂志

ABSTRACT

Objective To investigate the value of serum IgG4 in diagnosis of IgG4-RD and in differentiation from rheumatic diseases.Methods Total of 23 patients with IgG4-RD and 502 patients with rheumatic diseases were enrolled,who presented at Changhai Hospital in 2010 to 2011.In the study,rheumatic diseases were categorized into groups of Sj(o)gren syndrome (n =26),ankylosing spondylitis (n-50),systemic sclerosis (n =3),rhcumatoid arthritis (RA,n =125),mixed connective tissue disease (n =15),systemic lupus erythematosus (SLE,n =212),adult onset still disease (n =20),Behcet syndrome (n =17),polymyositis (n =12),dermatomyositis (n =12),polymyalgiarheumatica (n =10).Serum IgG and IgG4 levels were measured by a rate nephelometer assay.The ROC curves were constructed to identify the optimal serum IgG4 cutoff value for diagnosing IgG4-RD and evaluate its sensitivity and specificity.Results The mean levels of serum lgG4 in the group with IgG4-RD were 11.4(5.0-14.8) g/L.In about 95.6％ IgG4-RD patients,the serum IgG4 level was higher than ＞ 1.4 g/L and other rheumatic diseases (U values were 6.0,21.0,0,58.5,0,9.0,3.0,4.0,0,3.0,3.5,P ＜0.01).The levels of serum IgG4 with RA was 0.6(0.3-1.2) g/L,the levels of serum IgG4 with SLE was 0.2 (0.1-0.4) g/L.There were statistical differences between RA and SLE (U value was 5847,P ＜ 0.01).At the same time,some patients with other rheumatic diseases were found serum IgG4 level higher than ＞ 1.4 g/L,which was about 10％ in the patients whith RA,ankylosing spondylitis,adult onset still disease and polymyalgiarheumatica.According to the ROC constructed the cut off value in present study was 2.2 g/L,and sensitivity and specificity were 95.7％ and 97.4％,respectively.Area under the cerve (AUC) was 0.995.There were no significant differences between the sensitivity and specificity values obtained with a cutoff value of 2.2 g/L.In patients with other rheumatic diseases,the ratio of high serum IgG4 level (＞ 2.2 g/L) were declined obviously,except polymyalgiarheumatica,it was less than 10％.For differentiation from rheumatic diseases specificity values were higher.Conclusions The cut off value of 2.2 g/L is useful for diagnosing IgG4-RD,and in differentiation from rheumatic diseases.The high serum IgG4 concentrations are not specific to IgG4-RD.The cut off value of 2.2 g/L is better to diagnose IgG4-RD,and contributes to the differential diagnosis of IgG4-RD and other rheumatic diseases,but it needs to be further confirmed in clinical practice.