Lung scintigraphy with nonspecific human immunoglobulin G ((99m)Tc-HIG) in the evaluation of pulmonary involvement in connective tissue diseases: correlation with pulmonary function tests (PFTs) and high-resolution computed tomography (HRCT)

Abstract

Purpose: In patients with connective tissue diseases (CTD), the early detection and evaluation of the severity of the pulmonary involvement is mandatory. High-resolution computed tomography (HRCT) and pulmonary function tests (PFTs) are considered to be valuable noninvasive diagnostic modalities. Radiopharmaceuticals have also been used for this purpose. Our aim was the evaluation of technetium-labeled human polyclonal immunoglobulin G (HIG) lung scintigraphy in the early detection and assessment of the severity of the pulmonary involvement in CTD patients.

Methods: Fifty-two nonsmoking CTD patients were studied by PFTs, HRCT, and HIG. According to PFTs, patients were divided in group A (impaired PFTs-abnormal pulmonary function) and group B (normal pulmonary function). Semiquantitative analysis was done on HIG and HRCT and corresponding scores were obtained.

Results: Significant difference was found between HIG scores in the two groups (0.6 +/- 0.07 vs 0.51 +/- 0.08, P < 0.001). There was a statistically significant negative correlation between HIG scores and PFTs results and a positive correlation between HIG and HRCT scores. HIG demonstrated similar clinical performance to HRCT. At the best cut-off levels of their score (0.56 and 7, respectively), HIG had a superior sensitivity (77.5 vs 57.5%) with lower specificity (75 vs 91.7%). The combination of the two methods increased the sensitivity of abnormal findings at the expense of specificity.

Conclusions: HIG scintigraphy can be used in the early detection and evaluation of the severity of the pulmonary involvement in CTD, whereas, when used in combination with HRCT, the detection of affected patients can be further improved.