Dr. Cotton and her associates, therefore, wondered if there was a chance that patients being diagnosed with IPF actually could have covert CTD-associated ILD; this is an important distinction to make because the treatment differs for the two conditions. While ILD associated with CTD has a strong inflammatory component and is treated with corticosteroids and immunosuppressants, steroids can be harmful and increase mortality in IPF-ILD. The latter is treated with antifibrotic medications, such as pirfenidone and nintedanib.
For the study, serum samples from 250 patients with a definite diagnosis of IPF who were participating in the UK-BILD study were obtained and screened for known CTD antibodies using immunoprecipitation. Antibodies could be detected in just five (2%) patients – these included one patient each with anti-KS and anti-OJ antibodies, which are antisynthetase antibodies that are associated with myositis. Anti-Ku, another myositis-associated antibody, was identified in another patient, and one patient had an anti-RNA polymerase II antibody, which is associated with systemic sclerosis. Antimitochondrial autoantibodies were observed in one patient, and these are linked to primary biliary cirrhosis, which the patient was known to have.
There was nothing remarkable between the patients who did and did not have CTD antibodies in terms of their demographics, 76% and 80% were male, the mean ages were 73 and 70 years, respectively, and all were white.
However, 40% of patients did have unknown strong bands on immunoprecipitation, Dr. Cotton reported. This could suggest that there is an underlying immunological component to IPF, she added, but they had no recognized antibodies.