Increased pertechnegas lung clearance in interstitial lung disease.
BACKGROUND: Interstitial lung disease (ILD) is characterized by inflammation within the alveolar walls and interstitium of the lungs. This causes increased alveolar-capillary membrane permeability. The diagnosis is made by clinical features, chest roentgenography, lung function tests, and high-resolution CT, and it is confirmed by lung biopsy. Radionuclide aerosol tracers such as Tc-99m DTPA show increased lung clearance in ILD. The clearance rate of microaerosol pertechnegas (modified Technegas) from the lungs in the assessment of ILD was evaluated. METHODS: Thirty-two patients (22 with ILD and 10 with non-ILD) were evaluated with pertechnegas. Pertechnegas is formed by adding 3% oxygen to technegas, a microaerosol ventilation agent. Regions of interest were then drawn around the lungs, and clearance rates were determined from the best exponential fit. RESULTS: The mean clearance rate of pertechnegas was significantly increased in ILD and measured 5.78 +/- 2.2 minutes compared with non-ILD, which measured 8.53 +/- 2.42 minutes (P < 0.001). The sensitivity and specificity rates of pertechnegas clearance (less than 8 minutes) in ILD were 90% and 60%, respectively. When combined with chest roentgenography, the sensitivity and specificity rates increased to 100% and 90%, respectively. CONCLUSIONS: Pertechnegas is highly effective in determining the presence of active ILD. It differentiates between active ILD and non-ILD, and it is highly sensitive and specific when combined with chest roentgenography. Its potential role in the management of ILD merits further investigation.