We investigated the retinal findngs in eleven patients with diabetes mellitus during interferon (IFN) therapy for chronic type C hepatitis. Fundic examinations were performed periodically before and at 1 week, 2 weeks and 4 weeks and every month after IFN therapy. In eight of nine patients (88.9%) free of diabetic retinopathy before IFN therapy, retinal abnormalities, dot or patchy hemorrhage and cotton-wool spots, developed during IFN therapy. In another two patients with diabetic retinopathy before IFN therapy, retinal hemorrhage worsened. Therefore, we considered that diabees mellitus was a risk factor for retinal abnormality during IFN therapy. Fortunately, these abnormalities were not severe and did not exacerbate during IFN treatment except for one patient with diabetic retinopathy before IFN therapy, whose visual acuity was impaired. Thus we should use IFN carefully for diabetic patients.
On the basis of the previous interim report of this committee, it became apparent that there was a big variation in the measured values of HbA1c among the participants and this large interlaboratory variation was mainly due to differences in evaluation of a labile HbA1c component and in values measured with an instrument of one manufacture and with the other. In the present study we investigated whether standardizing to measure only stable component using common calibrators was useful to reduce the large interlaboratory variation. If it is so, the reference intervals of HbA1c value will be established using the standardized procedure. The committee sent a set of materials (two lyophilized erythrocyte hemolysates, two similarly processed calibrators and each one of fresh blood samples obtained from a healthy person and a diabetic patient) to 110 institutes and asked to measure stable HbA1c percentage in the materials. To assign HbA1c percentages to calibrators, we used HbA1c results from 100 participants who sent us the data good enough to evaluate judgingc from their chromatograms. Two-point calibration with assigned values improved interlaboratory variation as follows; CV with and without calibration, lyophilized hemolysate 1. 1.98% and 5.33%, lyophilized hemolysate 2, 1.43% and 3.24%, normal fresh blood, 3.88% and 7.76%, and diabetic fresh blood, 2.82% and 3.53%. We concluded that this standardized procedure i.e. measuring only stable HbA1c component and correcting the HbA1c percentages thus obtained with the assigned value of the calibrators, is useful to reduce the interlaboratory variation to the clinically desirable level of 4.0% which was calculated from data of the questionnaire to about 100 qualified diabetologists in Japan. The reference intervals of HbA1c percentage calculated from HbA1c results of 725 healthy subjects measured using the standardized procedure was from 4.3% to 5.8%.