Values of serum IgG4, IgG4/IgG ratio,and IgG4/IgG1 ratio in the diagnosis of Mikulicz′s disease / 中华检验医学杂志

ABSTRACT

Objective To evaluate values of Serum IgG 4,IgG4/IgG ratio,and IgG4/IgG1 ratio for distinguishing Mikulicz′s disease(MD)from primary Sj?gren′s syndrome(pSS).Methods It retrospectively analyzed 186 patients subjected to serum IgG subclass testing to differentiate MD from primary Sj?gren′s syndrome(pSS)at Peking University People′s Hospital from July 2012 to July 2016.This sample included 42 MD patients and 144 pSS patients.Serum IgG subclass concentrations were measured using Siemens reagents with nephelometry and BNⅡinstrument.In partial patients,serum antinuclear antibodies (ANA)were detected by indirect immunofluorescence assay, and serum anti-SSA antibodies and anti-SSB antibodies were detected by Western blot.Serum IgG subclass test results,ANA test results,serum anti-SSA antibody,and anti-SSB antibody test results were collected.The quantitative data were represented by median(quantile range).The Mann-Whitney U test was used to compare the medians between the two groups.Categorical variables were analyzed with a χ2test and were shown as percentages.The ROC curve was constructed to identify the optimal cut-off values and the area under the curve(AUC)values of the serum IgG4,IgG4/IgG ratio,and IgG4/IgG1 ratio for distinguishing MD patients from pSS patients.Results The medians of serum IgG4, IgG4/IgG ratio and IgG4/IgG1 ratio in MD patients were 11 200 mg/L(17 330),0.444(0.314)and 1.318(1.920), as compared with 329 mg/L(490),0.016(0.025)and 0.023(0.039)respectively in pSS patients(Z=-9.368, -9.560, and -9.571, respectively, P<0.001).For distinguishing MD from pSS, the optimal cut-off values of serum IgG4, IgG4/IgG ratio, and IgG4/IgG1 ratio were 1 870 mg/L,0.111, and 0.206, respectively.The corresponding AUC values were 0.976,0.985,and 0.986,respectively.Comparison of the ROC curves showed that there was no significant difference between AUC of serum IgG4/IgG ratio and IgG4/IgG1 ratio(Z=0.283, P=0.777).But AUC of serum IgG4/IgG ratio and IgG4/IgG1 ratio were significantly higher than AUC of serum IgG 4(Z=2.360 and 1.975,repectively,P=0.018 and 0.048,respectively).The positive rates of serum ANA in MD and pSS group were 10%and 85.8%,respectively(χ2=71.340,P<0.001).The positive rates of anti-SSA antibody and anti-SSB antibody in MD were 6.7%and 0%,respectively.Compared to 72.3%and 38.3%in pSS group, they were lower(χ2=44.773 and 16.792, P<0.001).Conclusions Measurements of serum IgG4 concentration,IgG4/IgG ratio, and IgG4/IgG1 ratio were of important values in differentiating MD from pSS.Serum IgG4/IgG ratio or IgG4/IgG1 ratio was superior to serum IgG4.