| Objective 1.To determine the reference interval of adult serum myeloperoxidase-anti-neutrophil cytoplasmic antibodies(MPO-ANCA)by enzyme-linked immunosorbent assay(ELISA)for our laboratory.2.To analyze the clinical disease spectrum of newly diagnosed MPO-ANCA positive patients,find the cut-off value of MPO-ANCA in the diagnosis of ANCA associated vasculitis(AAV),evaluate the value of MPO-ANCA combined with serum creatinine(Scr)in the diagnosis of AAV and explore the clinical significance of MPO-ANCA in the diagnosis of AAV or other diseases.Methods 1.A total of 360 serum samples of healthy adults were randomly collected from the health examination center of Qingdao Municipal Hospital(Dongyuan District)from September to December 2020.The serum MPO-ANCA levels were detected by enzyme-linked immunosorbent assay(ELISA)and the reference interval of our laboratory was established according to the stratified statistical analysis of sex and age.2.Retrospective revive of 152 inpatients identified as MPO-ANCA positive in Qingdao Municipal Hospital from July 2017 to June 2019.According to whether they were diagnosed as AAV or not,they were divided into AAV group and non AAV group.Comparison of clinical characteristics and laboratory examination indexes between the two groups.The receiver operating characteristic(ROC)curve was drawn according to the results of MPO-ANCA and the ROC curve was drawn according to the maximum value of Youden index to find the cut-off value of MPO-ANCA in the diagnosis of AAV and to evaluate the value of MPO-ANCA and its combination with serum creatinine(Scr)in the diagnosis of AAV.Results 1.The distribution of serum MPO-ANCA in adults was non-normal and there was no significant difference in gender and age(P>0.05).The reference interval of serum MPO-ANCA detected by ELISA in our laboratory was<2.48U/m L which was lower than the reference interval provided by the manual(<5.0 U/m L).2.Among 152 newly diagnosed MPO-ANCA positive patients,41 cases(26.97%)were diagnosed as AAV,19 cases were female,22 cases were male,aged 26-90 years old with an average age of(68±14)years old and 111 cases(73.03%)were non AAV,65cases were female,46 cases were male,aged 17-95 years old with an average age of(69±14)years old.There were no significant differences in gender and age between the two groups(P>0.05).The most common indications of MPO-ANCA were cough,expectoration(32.24%),fever(18.42%),abnormal renal function(17.76%),dizziness and headache(13.16%).41 patients with AAV were admitted to 8 clinical departments of our hospital mainly Nephrology department(41.46%),Respiratory department(19.51%),Department of Immunology and Rheumatology(17.07%).111 patients with non AAV were admitted to 14 clinical departments of our hospital mainly Respiratory department(29.73%),Neurology department(17.12%),Nephrology department(16.22%).Among the 41 AAV patients,microscopic polyangiitis(MPA)(n=38,92.68%)was the most common followed by eosinophilic granulomatosis with polyangiitis(EGPA)(n=2,4.88%)and granulomatosis with polyangiitis(GPA)(n=1,2.44%).Among the 111patients with non AAV,pulmonary diseases(n=36,32.43%)were the most common mainly pulmonary interstitial fibrosis with infection(12/36)followed by stroke(n=22,19.82%),kidney diseases(n=15,13.51%),connective tissue diseases(n=11,9.91%),Gatrointestinal tract diseases(n=7,6.31%),malignant tumor(n=4,3.60%),etc.3.The median MPO-ANCA titer and serum creatinine(Scr)titer in AAV group were44.80(14.00,78.80)U/m L and 139.83(67.81297.10)mmol/L which were significantly higher than those in non-AAV group 8.72(6.42,18.99)U/m L and 68.67(59.47,103.23)mmol/L(P<0.01).In AAV group,the increase rate of CRP and ESR,the incidence of hematuria and proteinuria and the rate of patients with moderate to severe chronic renal failure(e GFR<60ml/min/1.73m~2)were higher than those in non-AAV group(P<0.05).The positive rate of antinuclear antibody in non-AAV group was higher than that in AAV group(69.12%and 44.84%,P=0.024).4.The receiver operating characteristic(ROC)curve of MPO-ANCA distinguishing AAV and non AAV patients was AUC 0.793,95%confidence interval(CI)was 0.720～0.855,Z=7.394,P<0.01.According to the maximum value of Youden index 0.478,the cut-off value of MPO-ANCA for AAV diagnosis was>30.88U/ml,the sensitivity was65.90%and the specificity was 82.00%.The ROC-AUC of MPO-ANCA combined with serum creatinine(Scr)was 0.816,95%CI was 0.745～0.874.There was no significant difference between MPO-ANCA combined with Scr and MPO-ANCA in the independent diagnosis of AAV(Z=0.728,P=0.466).Conclusions 1.The reference range of serum MPO-ANCA of apparent healthy adults of our laboratory was preliminarily established.It provided accurate laboratory data for clinicians to diagnose MPO-ANCA related diseases.2.The clinical disease spectrum of newly diagnosed MPO-ANCA positive patients was very broad and the rate of non-AAV patients was high,the departments were scattered and the clinical symptoms were diverse.The establishment of cut-off value of MPO-ANCA in the diagnosis of AAV had a certain guiding significance for clinical practice,which needed further verification.The interpretation of MPO-ANCA positive results should be combined with clinical manifestations,laboratory examination and other information comprehensive analysis. |
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