The purpose of this study is to evaluate the clinical utility of specific autoantibody testing in unmasking an underlying connective tissue disorder in patients who present with interstitial lung disease and found to have weak positive ANA (1:400 titre) with no overt connective tissue disease manifestations OR borderline/negative ANA with some clinical suggestion of connective tissue disease.

It has been well established that patients with connective tissue disease associated interstitial lung disease respond better to immunosuppressive therapy, and have a better outcome compared to patients with idiopathic interstitial pneumonias. This makes it imperative to identify this group of patients for management and prognostication. Unfortunately some of these patients do not demonstrate overt clinical manifestations of connective tissue disease and our current available autoantibody screen does not detect all potential autoantibodies present. We would like to test for specific autoantibodies in this group of patients to evaluate its clinical utility in identifying covert connective tissue diseases associated with interstitial lung disease.

Inclusion Criteria:

1. Patients 21 years old and older
2. Patients with interstitial lung disease who have been found to have weak positive ANA (1:400 titre) with no overt connective tissue disease manifestations OR borderline/negative ANA with some clinical suggestion of connective tissue disease will be offered specific autoantibody testing

Exclusion Criteria:

1. Inability and unwillingness to sign informed consent
2. Patients who are pregnant or have underlying malignancy

Patients with weak positive ANA (1:400 titre) and no overt connective tissue disease manifestations OR borderline/negative ANA with some clinical suggestion of connective tissue disease.