Outcomes Study: 8-Year Experience of Patients With Isolated Reduction in Diffusion Capacity (Dlco)

Abstract

PURPOSE: Isolated reduction in DLCO poses a dilemma for the clinician as an explanation remains elusive in most cases. This study examines disease associations in this group of patients. METHODS: 117 patients with normal spirometry, normal thoracic gas volumes and isolated reduction in DLCO (< 70% predicted) were identified using electronic patient record search from 12/2002 to 3/2009. data was abstracted: age, race, gender, BMI, history of smoking, hypertension, diabetes, obstructive sleep apnea, thromboembolism, chest imaging, perfusion scans, cardiac echo, and rheumatologic markers. RESULTS: The average DLCO was 56% predicted (range 70-29%) with a mean age was 66 years (range 24-92); 86.3% were females. 59.0% of patients were smokers The mean BMI was 31.5 (range 16-62). 24.8% of the patients were diabetic; 66.7% had hypertension. Diseases commonly associated with a reduction in DLCO were identified in 33 patients (28.2%), 84 patients remained with no observed etiology (71.8%). In the cohort of 33 patients the following disorders were seen: Obstructive airway disease (n=12,36.4%), interstitial lung disease (n=14,42.4%), pulmonary vascular disease (n= 4,12.1%), and extrapulmonary diseases in 3 (9.1%). In the 84 patients with elusive diagnosis the following findings or disease associations were seen: LV diastolic dysfunction in 20 (23.8%), Obstructive sleep apnea in 20 (23.8%), Reactive airway disease in 18 (21.4%), Breast cancer by history in 11 (13.1%), history of Radiation therapy in 8 (9.5%), and Inflammatory bowel disease in 2 (2.4%). CONCLUSION: The etiology of isolated reduction in DLCO remains unclear in majority of the patients. Obstructive airway disease with normal spirometry, left ventricular diastolic dysfunction, obstructive sleep apnea and breast cancer are disease associations in this subgroup. Larger studies with databases are needed to define the long-term significance of these findings. CLINICAL IMPLICATIONS: Isolated reduction in DLCO although commonly evaluated with pulmonary and cardiac studies often have other disease associations.