PURPOSE: It is generally believed that connective tissue disease-related interstitial lung disease (CTR-ILD) has a better prognosis than idiopathic pulmonary fibrosis (IPF). We aimed to measure and compare trends in disease progression in both these groups.
METHODS: Through a retrospective cohort design, medical records of patients presenting to the Emory Interstitial Lung Disease clinic with either CTR-ILD or IPF were reviewed for medications used and trends in both pulmonary function tests and radiographic findings.
RESULTS: Thirty-nine patient records were reviewed (27 IPF; 12 CTR-ILD). Both groups had similar lengths of time since symptom onset leading up to initial presentation at our referral clinic (medians: 18 months IPF; 11 months CTR-ILD; p=0.70). There was no difference in the proportion of patients receiving immunosuppressive medications in each group (p=0.16). Initial forced vital capacity was similar for both groups (2.7±0.2L IPF; 2.1±0.2L CTR-ILD; p=0.14). Over the next 12 months, both groups showed a similar decline in most physiological parameters. However, patients with IPF showed a more rapid decline in diffusing capacity for carbon monoxide (DLCO; 2.4±0.8 ml/min/mmHg IPF; -1.0±1.3 ml/min/mmHg CTR-ILD; p=0.03) as well as in radiographic progression of disease (p=0.04).
CONCLUSION: We found that subjects with CTR-ILD and IPF showed similar deterioration in most physiological parameters during our 12-month period of study. However, deterioration in DLCO and radiographic progression of disease were more rapid in patients with IPF. Of note, our retrospective design precluded matching the two groups for elimination of possible confounders and for accurately measuring and comparing progression of symptoms.
CLINICAL IMPLICATIONS: In general, the diagnosis of interstitial lung disease carries a poor prognosis especially in the case of IPF. CTR-ILD is also associated with rapid deterioration of lung function, but is generally believed to show some responsiveness to therapy and carry a better prognosis than IPF. Our data, generated in a 'real world' setting, re-affirm that impression while evaluating DLCO and radiographic progression, and suggest that DLCO might be the best marker of disease progression when evaluating these disorders.
DISCLOSURE: Majid Shafiq, No Financial Disclosure Information; No Product/Research Disclosure Information