Diabetes Care, Vol 20, Issue 12 1900-1903, Copyright © 1997 by American Diabetes Association
Antibodies to GAD and glycemic control in recent-onset IDDM
RD Hoeldtke, KD Bryner, GG Horvath, MR Byerly, GR Hobbs, SM Marcovina and A Lernmark
Department of Medicine, West Virginia University, Morgantown 26506-9159, USA. bmusick@wvudeptmed1.hsc.wvu.edu
OBJECTIVE: To analyze the effect of antibodies to glutamic acid
decarboxylase (GAD65Ab) and islet cells (ICA512Ab) on glycemic control
early in IDDM. RESEARCH DESIGN AND METHODS: GAD65Ab and ICA512Ab were
measured twice in 35 patients (10 male, 25 female; age 10-40 years)
initially within 2 years of diagnosis and again 1 year later. The
glycosylated hemoglobin was measured one to four times each year, and the
average glycosylated hemoglobin for the preceding year was calculated each
time the antibodies were measured. RESULTS: The mean HbA1 at the time of
the initial evaluation was 8.04 +/- 0.30 (reference range 4.7-7.3% for
nondiabetic patients), the average GAD65Ab index was 0.735 +/- 0.306, and
the mean ICA512Ab index was 1.94 +/- 0.65. The GAD65Ab index correlated
with HbA1 (r = 0.41, P < 0.025), whereas the ICA512Ab index did not (r =
0.13). One year later, the mean GAD65Ab index was 0.94 +/- 0.34, the mean
ICA512Ab index was 1.04 +/- 0.40, and the mean HbA1 was 9.03 +/- 0.30. The
GAD65Ab index correlated with HbA1 (r = 0.61 P < 0.001), whereas the
ICA512Ab index did not (r = -0.06). Stratification of patients into
tertiles according to the average GAD65 index revealed, at the follow-up
evaluation, that the better glycemic control in the lowest GAD65Ab tertile
was accomplished with significantly less insulin (0.43 +/- 0.08 U/kg for
the lowest tertile vs. 0.71 +/- 0.09 and 0.64 +/- 0.09 for the middle and
highest tertiles, respectively; P < 0.05). CONCLUSIONS: In summary,
patients with IDDM and low GAD65Ab have better glycemic control even though
they require less insulin. The ICA512Ab index, however, fails to correlate
with glycemia.