Low body mass index and lymphocytopenia associate with Mycobacterium avium complex pulmonary disease in patients with rheumatoid arthritis

Abstract

Objectives: Patients with rheumatoid arthritis (RA) are at an increased risk of Mycobacterium avium complex pulmonary disease (MAC-PD). We aimed to identify factors associated with MAC-PD in RA patients, and investigate their clinical significance for diagnosis of this disease.

Methods: We examined 396 patients with RA for the presence of MAC-PD, using the criteria of the American Thoracic Society and conducted three years of follow-up on these patients. Multivariate logistic analyses were employed for selecting factors associated with MAC-PD. We developed a point system based on these factors which we call MAC-PD score to improve diagnosis of MAC-PD.

Results: During this study, 14 out of 396 patients were newly diagnosed with MAC-PD. Multivariate analyses revealed body mass index (BMI) <18.0 kg/m² and lymphocyte count <1500/μl were associated with MAC-PD in RA patients. Points were assigned to them and totalled to provide the MAC-PD score. Among 20 patients with high-resolution computer tomography images consistent with MAC-PD, the scores were significantly higher in 14 patients with MAC-PD than those in six patients without MAC-PD.

Conclusion: Using these data, in the forms of the MAC-PD score, could help to identify patients who should be considered for bronchoscopy more selectively.

Keywords:

• Rheumatoid arthritis
• Mycobacterium avium complex pulmonary disease
• lymphocytopenia
• low BMI

Acknowledgements

We would like to thank Dr. Shigeo Kamitsuji at Stagen for helping with the statistical analyses.

Conflict of interest

None.

Funding

The authors received no specific funding for this work.