Correlation of monocyte counts with clinical outcomes in seropositive rheumatoid arthritis-related interstitial lung disease: a case-control study.

INTRODUCTION

Higher blood monocyte count is associated with worse survival in patients with interstitial lung disease (ILD), including idiopathic pulmonary fibrosis (IPF). Herein, we investigated effects of blood monocyte count on seropositive rheumatoid arthritis (SPRA) associated with ILD.

METHODS

In this retrospective study, we reviewed electronic medical records of 423 patients coded as 'SPRA' with evaluated baseline chest computed tomography (CT) between January 2001 and December 2020. After exclusions, 295 patients with SPRA were finally included. According to the latest CT scan, the ILD group was defined as having persistent or developing ILD including nonspecific interstitial pneumonia and usual interstitial pneumonia.

RESULTS

The mean patients' age was 62.3 (±11.9) years; 101 (34.2 %) patients were male. The mean follow-up duration was 81.4 months. The ILD group (91 [30.8 %] patients) was older and included more male than female patients. Monocyte counts were significantly higher in the ILD group than in the non-ILD group but rheumatoid factor (RF) or anti-cyclic citrullinated peptide (anti-CCP) levels were not significantly different. After adjusting for age and sex, higher monocyte counts were associated with ILD. The ILD group had a worse survival rate. In Cox proportional hazard analysis, older age and ILD were independent poor prognostic factors for survival. However, monocyte count was not an independent prognostic factor for survival.

CONCLUSIONS

SPRA, RF, and anti-CCP did not show a relationship with ILD or survival. A higher monocyte count at diagnosis might be associated with SPRA-associated ILD but was not an independent prognostic factor for survival.