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

Systemic thickening of capillary endothelial basement membrane underlies th e chronic complications of human diabetic microangiopathy. Since (99)mTc-DT PA aerosol scintigraphy is a sensitive, non-invasive test of membrane perme ability, 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, an d who were non-smokers, were subjected to evaluation using Tc-99m-DTPA aero sol. 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 Tc-99m-DTPA and pulmonary func tion tests, served as controls. The risk factors which included age, sex, d egree of control and presence of complications were noted. Twenty-nine (58%) of the patients had abnormal Tc-99m-DTPA clearance. Thirt y-four percent of the patients with complications and 24% of those without complications had abnormal clearance. Complications recorded included retin opathy, neuropathy and nephropathy. Fifty-five percent of patients with abnormal Tc-99m-DTPA had suffered from diabetes for longer than 10 years. Sixty-two percent of patients with poor glycaemic control had abnormal Tc-99m-DTPA. Diffusion capacity was not sign ificantly affected in patients with complicated diabetes. Our preliminary results suggest that Tc-99m-DTPA is a potentially sensitive test in assessing the degree of lung affection in diabetic patients. No si gnificant correlation exists between diffusion capacity and Tc-99m-DTPA. Th e risk factors did not affect the Tc-99m-DTPA clearance, probably due to th e small sample size.