Technetium 99mTc-DTPA clearance in the evaluation of pulmonary involvement in patients with diabetes mellitus

Abstract

Systemic thickening of capillary endothelial basement membrane underlies the chronic complications of human diabetic microangiopathy. Since 99mTc-DTPA aerosol scintigraphy is a sensitive, non-invasive test of membrane permeability, we decided to study the effect of diabetes on the permeability of lung epithelium in diabetic patients using this test. Fifty (NIDDM) patients, aged 40-70 years, with or without complications, and who were non-smokers, were subjected to evaluation using 99mTc-DTPA aerosol. At the same time, pulmonary function tests, including carbon monoxide diffusion capacity, were done. Normal non-smoking subjects with no history of cardio-respiratory disease, who underwent 99mTc-DTPA and pulmonary function tests, served as controls. The risk factors which included age, sex, degree of control and presence of complications were noted. Twenty-nine (58%) of the patients had abnormal 99mTc-DTPA clearance. Thirty-four percent of the patients with complications and 24% of those without complications had abnormal clearance. Complications recorded included retinopathy, neuropathy and nephropathy. Fifty-five percent of patients with abnormal 99mTc-DTPA had suffered from diabetes for longer than 10 years. Sixty-two percent of patients with poor glycaemic control had abnormal 99mTc-DTPA. Diffusion capacity was not significantly affected in patients with complicated diabetes. Our preliminary results suggest that 99mTc-DTPA is a potentially sensitive test in assessing the degree of lung affection in diabetic patients. No significant correlation exists between diffusion capacity and 99mTc-DTPA. The risk factors did not affect the 99mTc-DTPA clearance, probably due to the small sample size.