Anti-cyclic citrullinated peptide (anti-CCP) antibodies are a sensitive marker for rheumatoid arthritis (RA) in patients who also have pulmonary disease, say scientists. "Among the extra-articular involvements in RA, pulmonary complications are common and important causes of mortality," write Naoki Inui and associates from Hamamatsu University in Japan. "Apart from infections and drug-induced diseases that are indirectly associated with RA, airway, pleural, vascular, and parenchymal diseases can occur in RA patients," add the authors in the journal Clinical Biochemistry. To determine whether pulmonary disease affects the presence of anti-CCP antibodies in patients with RA, Inui and team tested for anti-CCP antibodies in 18 patients with RA, interstitial lung disease, and bronchiolitis. Results from these patients were compared with results from 36 individuals with RA and no pulmonary disorders. The prevalence of anti-CCP antibodies was the same (88.9%) in those with RA and pulmonary disorders and those with RA only. In addition, concentrations of anti-CCP did not differ significantly between RA patients with and without pulmonary disease, at 35.6 U/ml and 26.8 U/ml, respectively. The authors note that anti-CCP levels varied between patients with different forms of pulmonary disorder. For example, concentrations of anti-CCP were lower in those with interstitial pneumonia than in those with organizing pneumonia. Nevertheless, they conclude: "The positivity rates and levels of anti-CCP antibodies were high in RA patients independent of pulmonary complications, and these values did not differ between RA patients with interstitial lung disease and bronchiolar disease. "In addition, these antibodies may be practical for distinguishing between idiopathic and RA-associated interstitial lung disease preceding RA onset."
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