Background In rheumatoid arthritis (RA), pulmonary involvement is one of the important complication.Both organizing pneumonia (OP) and bacterial pneumonia (BP) can be evident during the course of RA. However, we often have difficulties with differentiating OP from BP clinically, because both present similar infiltrations in chest computed tomography (CT). Corticosteroid is the standard therapy for OP, on the other hand, antibiotics is necessary for BP.CD64 on neutrophils (nCD64) is FcγRI known to be upregulated as a response to infection.
Objectives To evaluate the usefulness of nCD64 for differentiating OP from BP.
Methods Eleven RA patients diagnosed as pneumonia with infiltrative shadows in their chest CT were enrolled in this study. Five patients were successfully treated only with predonisolone (PSL). Three of them were pathologically confirmed the tissue of lung lesions by transbronchial lung biopsy (TBLB). They were diagnosed as OP. Nine patients were successfully treated with only broad-spectrum antibiotics (ABx), diagnosed as BP. All patients received blood examinations before treatment and following parameters were examined. The expression level of CD64 per neutrophil (nCD64) was quantitatively measured by using flow cytometery. C-reactive protein (CRP) and procalcitonin (PCT) were also measured. Comparisons of levels within each group were analyzed using the Mann-Whitney's U-test.
Results nCD64 levels in OP were significantly lower than those in BP (p=0.0164). On the other hand, in CRP and PCT, there were no differences between OP and BP. Among these biomarkers, only nCD64 can distinguish OP from BP, indicating the efficacy of nCD64 for diagnosis of OP.
Conclusions nCD64 is an effective diagnostic marker for differentiating OP from BP in RA patients. This novel marker would be contribute to both early diagnosis and suitable treatment.
Disclosure of Interest None declared