¹⁸F-FDG PET/CT Manifestations Of Patients With Different Types Of Anti-neutrophil Cytoplasmic Antibody-associated Vasculitis

Objective:To investigate the characteristics of ¹⁸F-2-deoxy-2-[18F]fluoro-D-glucose（FDG）positron emission tomography（PET）/CT in assessment of extent in patients with distinct subtypes of antineutrophil cytoplasmic antibodies-associated vasculitis（AAV）.Methods:A retrospective analysis of 19 cases of AAV diagnosed in the General Hospital of Tianjin Medical University from January 2010 to March 2019.All patients completed 21 18F-FDG PET/CT scans,including 19 baseline levels and 2follow-ups.Five patients with large-vessel vasculitis（LVV）and five healthy volunteers served as disease control group and healthy control group（HC）,respectively.The patient’s baseline clinical data include:multiple organ involvement（eye,ear-nose-throat,thyroid,lung,cardiovascular,kidney,gastrointestinal tract,bone marrow,skin/joint,nervous system）;laboratory indicators（c-reactive protein（CRP）,erythrocyte sedimentation rate（ESR））,Creatinine,D-dimer,myeloperoxidase（MPO）titer level,protease 3（PR3）titer level);activity score（Birmingham vasculitis activity score（BVAS）,five-factor score（FFS））;Observe and record the range of disease involvement,imaging characteristics,and the maximum standard uptake value（SUVmax）of the disease shown by ¹⁸F-FDG PET/CT.Moreover,two AAV patients were followed up to observe and record the changes in the maximum standard uptake value（SUVmax）of the lesions after treatment.The Mann-Whitney U test was used as appropriate to determine the difference between the unpaired groups.Correlation between continuous variables was tested using Pearson’s coefficient correlation.Statistical analyses were carried out using SPSS（version 19;IBM,Armonk,NY,USA）and Graphpad Prism（version 6.0;Graph Pad Software,La Jolla,CA,USA）software.Results:（1）AAV was microscopic polyangiitis（MPA）（n=12）,granulomatosis with polyangiitis（GPA）（n=6）and eosinophilic granulomatosis with polyangiitis（EGPA）（n=1）.In addition to skin,joints,eyes and peripheral nervous system,¹⁸F-FDG PET/CT could accurately identify organ involvement.（2）The FDG uptake tended to be higher in patients with GPA in comparison to patients with MPA,LVV and HC（median SUVmax:5.70 vs 5.65 vs 3.5 vs 2.90;p=0.004）.Organ involvement was different among the above,especially,in the nasopharynx,nasal mucosa,lung,hilar lymph node,pericardium,kidney.In terms of aortic involvement（aortic root,aortic arch,ascending aorta,and descending aorta）,comparing patients with large vasculitis,GPA,MPA,and healthy control:median SUVmax:3.0 vs 2.80 vs 2.05 vs2.0（p<0.005）.（3）Comparing MPA,the patients with GPA tended to exhibit a higher FDG uptake in ear-nose-throat,lung,kidney parenchymal and aorta.（4）Moreover,¹⁸F-FDG PET/CT revealed a wider range of AAV lesions than that clinically predicted including spleen,bone marrow,aorta,parotid gland and so on.（5）In addition,in MPA patients,the uptake in kidney（SUVmax）was positively correlated with serum CPR level（r=0.642,p=0.024）;vascular SUVmax was positively correlated with serum MPO levels（r=0.619,p=0.032）,and the SUVmax of other lesions had no significant correlation with serum CRP,ESR,MPO,and BVAS,FFS;In GPA patients,the SUVmax of the nasal mucosa was negatively correlated with serum ESR levels（r=-0.819,p=0.046）,and the SUVmax of other organs were not significantly correlated with serum CRP,ESR,PR3,and BVAS,FFS.（6）Lastly,the18F-FDG PET/CT of 2 GPA patients in remission showed that the SUVmax of the lesion was significantly reduced or even decreased to physiological intake.Conclusion:（1）18F-FDG PET/CT accurately identifies the organ impairment（especially,ear-nose-throat,lung,kidney）to assist clinical diagnosis.The different positive findings of ¹⁸F-FDG PET/CT in MPA and GPA can help distinguish GPA from MPA.（2）To some extent,it can found that PET-positive sites in AAV which were unsuspected based on the clinical evaluation,which helps to clarify the severity of disease in AAV patients.