Ascertainment of collagen vascular disease in patients presenting with interstitial lung disease

Introduction: Previous studies of interstitial lung disease (ILD) suggest that prognosis and therapeutic response are influenced by the presence of underlying collagen vascular disease (CVD). Yet, what proportion of patients presenting with ILD have CVD is largely unknown. We sought to determine the frequency of a new CVD diagnosis in an ILD referral population. Materials/patients and methods: We retrospectively studied 114 consecutive patients evaluated at the Johns Hopkins Interstitial Lung Disease Clinic for the development of CVD. Results: In this retrospective cohort, nearly one-third of the 114 patients with confirmed ILD satisfied published criteria for a CVD diagnosis. Seventeen (15%) patients were diagnosed with a new CVD as a direct consequence of their ILD evaluation. Patients with new CVD diagnosis were younger than those without new CVD diagnosis: 51.4 years (95% CI 45-58 years) and 60 years (95% CI 57-63), respectively (p = 0.01). Moreover, an ANA ≥ 1:640 (p = 0.03) and elevated levels of creatine phosphokinase (CPK) or aldolase (p < 0.001) were associated with a new CVD diagnosis. Conclusions: Unrecognized collagen vascular disease may be more common than previously appreciated among patients referred with ILD. High titer ANA and an elevated CPK or aldolase are associated with a CVD diagnosis in this referral population.