EARLY PULMONARY INVOLVEMENT IN SYSTEMIC-SCLEROSIS ASSESSED BY TECHNETIUM-99M-DTPA CLEARANCE RATE

Systemic sclerosis (SS) is frequently associated with interstitial lun g disease, but clinical symptoms and radiologic abnormalities may occu r late in the course of the disease. This study investigated early pul monary involvement by assessing the clearance rate of inhaled Tc-99m-d iethylenetriaminepentaacetic acid (DTPA). Methods: Sixteen patients wi th proved SS, no clinical pulmonary symptoms and normal chest radiogra m were prospectively studied. The Tc-99m-DTPA clearance rate was calcu lated as the time to half clearance (T-1/2) and compared with values o btained in healthy nonsmokers. Results: Six patients showed abnormally increased clearance (T-1/2 < 53 min). Rapid clearance was not correla ted to SS disease duration or to abnormal pulmonary function tests. Fi ve of six patients with abnormally increased clearance underwent high- resolution CT, which in all five demonstrated pathologic findings that were suggestive of early interstitial disease. Conclusion: These find ings indicate that in SS asymptomatic patients may frequently present with abnormal Tc-99m-DTPA clearance; Tc-99m-DTPA lung scintigraphy may allow early detection of subclinical pulmonary involvement in SS.