The authors investigated a group of 47 type I diabetics in a prospective study extending over 8 years. Every year they evaluated the albuminuria and the N-acetyl-beta-glucosaminidase (NAG) activity in serum and urine and the results were compared with the state of compensation of diabetes and with the clinical finding on the ocular fundus. During the eight-year period newly manifested microalbuminuria developed in 8 of 32 patients (25%) who at the onset had a normal finding. In patients with newly manifested microalbuminuria the authors found a significant rise of the fructosamine serum concentration (p0.05) and at the same time a rise of serum NAG activity (p0.05). A positive correlation was proved between the serum NAG activity and glycated haemoglobin (r = 0.67, p0.01). In 13 patients (28%) in the course of the eight-year period the finding on the ocular fundus deteriorated. In these patients the NAG serum activity was elevated already at the onset of the investigation, while albuminuria rose in the course of the mentioned period. Dynamic changes of the NAG serum activity along with albuminuria can serve as bio-chemical markers of developing microangiopathy the manifestation of which is hastened by deteriorated compensation of diabetes.
