Introduction: Greater glycaemic variability (GV) is associated with higher risk of severe hypoglycaemia and chronic complications in T1D (1-7). CSII may improve short-term GV (measured by continuous glucose monitoring (CGM) and self-monitoring of blood glucose (SMBG)) (8-10). CSII can decrease long-term GV (HbA1c variability) in children, but has not been evaluated in adults (11).
Objectives: Compare HbA1c variability in T1D patients using CSII or MDI.
Methods: Cross-sectional and longitudinal studies were conducted by audit of electronic records (2010-2016) of T1D patients (Royal North Shore, Sydney and St Vincent’s Hospital, Melbourne). GV was determined by HbA1c standard deviation (SD) and coefficient of variation (CV) of 7+/-4 (MDI) and 7+/-5 (CSII) HbA1c values overall, and in a subset of patients, GV was compared pre vs. post CSII use, (excluding HbA1c for 12 months post-CSII initiation during HbA1c improvement). Analyses were by Mann-Whitney, Wilcoxon Signed Rank and Chi Squared tests and significance taken at p<0.05.
Results: T1D patients (n=180; MDI, n=86; CSII, n=94) were assessed cross-sectionally over mean +/-SD 3+/-2 years, with similar age (42+/-14.2; 42+/-14.2y), T1D duration (20+/-14.7; 18+/-13.5y), HbA1c (8.0+/-1.5%; 7.7±1.2%), chronic complications (44%; 34%) and severe hypoglycaemia frequency on MDI/CSII respectively. More CSII users were female (82% vs. 48% respectively, P=0.001). There was less HbA1c variability amongst CSII (HbA1c SD 0.57±0.45% CSII vs. 0.84±0.81% MDI; P=0.02). HbA1c CV was lower in CSII vs. MDI (CV: 7.1+/-5.0 vs. 10.3+/-9.3 respectively, P=0.007). In 22 patients changing from MDI to CSII, HbA1c improved (7.8+/-0.8% MDI; 7.3+/-0.8% CSII, P=0.002). SD and CV of HbA1c also significantly decreased (mean SD 0.82+/-0.50% vs. 0.39 +/-0.26% respectively; P=0.001, mean CV: 10.5+/-6.5 vs. 5.4+/-3.9 respectively; P=0.002).
Conclusions: In T1D CSII therapy reduces GV vs. MDI as assessed by HbA1c SD and CV.