OMAHA, Nebraska—African-American rheumatoid arthritis (RA) patients who smoke are more likely to have both rheumatoid nodules and higher serum concentrations of IgA-RF (immunoglobulin A rheumatoid factor) than nonsmokers, and these associations are independent of the HLA-DRB1 shared epitope, according to the first study to examine the effect of smoking on RA-related disease characteristics in this population.

"The risk of higher IgA-RF concentrations appeared to be most pronounced in those with more than 20 pack-years of cumulative exposure," wrote Ted R. Mikuls, MD, who led the research study. Dr. Mikuls, of the University of Nebraska Medical Center, the Nebraska Arthritis Outcomes Research Center, and Omaha VA Medical Center, and colleagues reported the study early online in Annals of the Rheumatic Diseases.¹

The researchers studied 300 African-American patients with recent-onset RA. They examined the association of cigarette smoking (current vs past vs never, and pack-years of exposure), anti-CCP (cyclic citrullinated peptide) antibody, IgA and IgM RF levels, rheumatoid nodules, and baseline radiographic erosions. They also examined evidence of interaction between smoking status and SE for all outcomes.

The analysis showed the following:

• current smokers were twice as likely as never-smokers to have high IgA-RF concentrations
• current smokers were twice as likely as never-smokers to have rheumatoid nodules
• patients with >20 pack-years of exposure were most likely to have high IgA-RF levels and rheumatoid nodules
• smoking status and cumulative pack-years were not associated with anti-CCP or IgM-RF levels, or presence of radiographic erosions
• no association between smoking and RF-IgA seropositivity
• no association between any of these outcomes and an interaction between smoking and SE status

Translating research into practice

Dr. Mikuls wrote, "Cigarette smoking is associated with both subcutaneous nodules and higher serum concentrations of IgA-RF in African Americans with RA, associations that may have important implications for long-term outcomes in this population." High IgA-RF concentrations have been associated with higher rates of extra-articular disease manifestations, which are in turn associated with increased disease-related mortality.

The results of this study are particularly important because "the prevalence of smoking in African Americans appears to be increasing while ‘quit rates' in African Americans are lower compared to Caucasians, disease characteristics related to smoking portend a poor outcome in RA, and smoking appears to have a disproportionately negative impact on minority patients with select chronic conditions," the researchers concluded.

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