A comparison of the clinical features of ANCA-positive and ANCA-negative idiopathic pulmonary fibrosis patients.

BACKGROUND

The existence of antineutrophil cytoplasmic antibody (ANCA)-positive pulmonary fibrosis (PF) has recently been recognized.

OBJECTIVES

The aim of this study was to clarify whether there is any difference in the clinical features between ANCA-positive PF and ANCA-negative PF.

METHODS

A retrospective study was carried out on 53 patients with idiopathic PF whose myeloperoxidase (MPO)- and proteinase 3 (PR3)-ANCA levels were measured. After dividing the patients into ANCA-positive and ANCA-negative PF, we compared their symptoms, pulmonary function tests, chest CT findings, bronchoalveolar lavage findings, the effects of therapy and survival rates.

RESULTS

17 of the 53 patients with idiopathic PF were MPO-ANCA-positive, 2 were PR3-ANCA-positive and 34 were negative for both ANCA types. Lactate dehydrogenase was lower in ANCA-positive PF than in ANCA-negative PF. However, there was no significant difference in the symptoms, lung function tests, CT findings and bronchoalveolar lavage findings. Corticosteroid therapy tended to be more effective in ANCA-positive PF, but the overall survival rate in ANCA-positive PF was not different from that in ANCA-negative PF. However, the low-titer (<50 EU) group showed better survival than the high-titer (> or =50 EU) group in ANCA-positive PF. ANCA titers of the patients who developed microscopic polyangiitis were higher than of those who did not develop it in ANCA-positive PF.

CONCLUSIONS

Our studies showed little difference in the clinical features between ANCA-positive and ANCA-negative PF. However, it may be important to measure ANCA when idiopathic PF is diagnosed, because a high titer of ANCA suggests a poor prognosis and the association with microscopic polyangiitis.