Clearance of inhaled technetium-99m-DTPA as a clinical index of pulmonary vascular disease in systemic sclerosis.

This study evaluated the utility of the clearance time of inhaled diethylenetriamine pentaacetate (DTPA) to distinguish pulmonary vascular disease from early fibrosing alveolitis (FA) in patients with systemic sclerosis (SSc). It was hypothesized that this would be preserved in patients with vascular disease compared with FA, despite similar gas-transfer deficits and matching lung volumes, because of the preservation of alveolar epithelial integrity. All patients had SSc and were categorized into a control group (C; n=9), pulmonary vascular group (VAS; n=14) or FA group (n=14) dependent on the appearance on a computed tomography (CT) scan and the transfer factor of the lung for carbon monoxide (T(L,CO)) (VAS and FA < or =70%, C > or =80%). All patients had a forced vital capacity (FVC) of >80%. The T(L,CO) (median) was similar in the VAS (57.5%) and FA (60%) groups. There was a significant difference in median DTPA clearance half-times between FA (21.25 min) and VAS (46.5 min) (p=0.014) and between FA and C (84.5 min) (p=0.0004). No difference was found between VAS and C (p=0.0778). Follow-up data from the VAS group showed no subsequent development of FA on the CT scan and no decrease in FVC (n=13, mean 42 months). These results suggest that clearance of diethylenetriamine pentaacetate is preserved in patients likely to have pulmonary vascular disease and may be useful in distinguishing fibrosing alveolitis from vascular disease in systemic sclerosis.