Antinuclear antibodies in interstitial lung disease: Prevalence and clinical significance

The diagnosis of interstitial lung disease (ILD) requires elimination of underlying connective tissue disease. Consequently, antinuclear antibodies (ANA) are routinely screened in patients with idiopathic interstitial pneumonia. However the clinical usefulness of this practice is not well clear.

In this study, we evaluated the frequency of ANA in ILD's patients and investigated the clinical significance of the ANA's presence in these patients.

We conducted a retrospective study of hospitalized patients diagnosed ILD at pulmonary department and for which ANA was performed in the immunology laboratory of our institution. Demographic features, clinical symptoms, biological and radiologic findings and CTD-ILD diagnoses were compared between patients with positive ANA versus negative ANA.

We enrolled 73 patients. The ANA's prevalence was 32%. There were no significant differences in demographics, pulmonary function test values and radiologic findings between patients with and without ANA. Patients with positive ANA had more cutaneous manifestations (p꞊0.011) and Raynaud's phenomenon (p꞊0.029). The diagnosis of connective tissue disease was made in 42% of patients with positive ANA versus 8% with negative ANA (p꞊ 0.001). ANA's titer higher than 1/320 was predictive of CTD diagnosis (OR꞊14.4) (p<0.001).

The research of ANA in PID's patients is an important tool of CTD diagnosis specially in those with suggestive symptoms of autoimmune disease.