Background: Little is known about the frequencies and types of nonmetabolic complications occurring in type 1 diabetes patients being treated by modern insulin pump therapy (continuous subcutaneous insulin infusion [CSII]), when recorded by standardized questionnaire rather than clinical experience. Subjects and Methods: A self-report questionnaire was completed by successive subjects with type 1 diabetes attending an insulin pump clinic, and those with a duration of CSII of ‡ 6 months were selected for analysis (n = 92). Questions included pump manufacturer, insulin, infusion set type and duration of use, frequency of infusion set and site problems, pump malfunctions, and patient-related problems such as weight change since starting CSII. Results: Median (range) duration of CSII was 3.3 (0.5-32.0) years, and mean -SD duration of infusion set use was 3.2 -0.7 (range 2-6) days. The commonest infusion set problems were kinking (64.1% of subjects) and blockage (54.3%). Blockage was associated with > 3 days of use of infusion sets plus lispro insulin in the pump (relative risk [95% confidence interval], 1.71 [1.03-2.85]; P = 0.07). The commonest infusion site problem was lipohypertrophy (26.1%), which occurred more often in those with long duration of CSII (4.8 [2.38-9.45] vs. 3.0 [1.50-4.25] years; P = 0.01). Pump malfunction had occurred in 48% of subjects (43% in the first year of CSII), with ''no delivery,'' keypad, and battery problems commonly occurring. Although some patients reported weight gain (34%) and some weight loss (15%) on CSII, most patients (51%) reported no change in weight. Conclusions: Pump, infusion set, and infusion site problems remain common with CSII, even with contemporary technology.

The best glycaemic control achievable on MDI is related to blood glucose variability-those with the largest swings in blood glucose retaining the highest HbA(1c). The improvement in control achieved by CSII is related to HbA(1c) and blood glucose variability on MDI. Pump therapy is most effective in those worst controlled on MDI.

• The effectiveness of CSII has been poorly studied in hypoglycaemiaprone type 1 diabetic subjects, though they are prime candidates for insulin pump therapy • We found that HbA1c improved on CSII compared to MDI (including glargine) to a greater extent than expected from previous studies • We recommend that type 1 diabetic patients with frequent unpredictable hypoglycaemia during MDI should be included in NICE guidelines for CSII