R. Jorde et J. Sundsfjord, Intra-individual variability and longitudinal changes in glycaemic controlin patients with Type 1 diabetes mellitus, DIABET MED, 17(6), 2000, pp. 451-456
Aims Patients with Type 1 diabetes mellitus (DM) appear to have remarkably
stable HbA(1c) levels, regardless of the need for improvement. The purpose
of the present study was therefore to study predictors of intra-individual
variability of the HbA(1c) level together with changes in HbA(1c) over time
.
Methods Hospital records of patients with Type 1 DM seen at our diabetes cl
inic from February 1992 to May 1997 were reviewed for HbA(1c) measurements
and clinical data. In the main study, 214 patients who had been on insulin
for more than 1 year, and in a sub-study, 14 patients newly started on insu
lin, were included.
Results The coefficient of variation (CV) of the intra-individual HbA(1c) m
easurements, after at least 1 year of insulin, was 8.8 +/- 3.7% (mean +/- s
d). There was a positive association between the CV and the HbA(1c) measure
ment at inclusion in the study (P < 0.05), and also a negative association
between the CV and age (P < 0.05). Fifty per cent of the patients had a dif
ference between first and last HbA(1c) below 1%, and 83.6% had a difference
below 2%. In the sub-study, there was a positive association between the m
ean HbA(1c) value the first year on insulin (excluding the first 3 months)
and the last HbA(1c) measurement (P < 0.01).
Conclusions The HbA(1c) levels in individual patients remain remarkably sta
ble over time. Furthermore, the HbA(1c) level shortly after starting insuli
n is a predictor of future glycaemic control.