Title : Serum fructosamine: A more accurate screening test than 3-hour OGTT for diagnosis of gestational diabetes
Abstract:
Presently, ACOG and ADA recommend OGTTs for screening for diagnosis of Gestational Diabetes Mellitus (GDM). However, the validity of OGTTs is being questioned because OGTT results vary daily due to changing total content as well as type of carbohydrate intake during the previous few days, but especially the intake from dinner or bedtime snack the previous day. Their reliability and accuracy of OGTTs are further compromised by lack of recommended preparation. Recent studies documented continuous glucose monitoring (CGM) to be more reliable and accurate than OGTTs. Recently, we documented random serum Fructosamine concentration ≤ 198 mM/l with normal pregnancy and >198 mM/l in GDM, comparable to age matched non-pregnant women. However, some subjects with GDM based on 3-hour OGTT showed Fructosamine < 198 mM/l suggesting false positivity.
Objective: Therefore, we assessed comparisons between Fructosamine and CGM for 2 weeks on one aspect, and 3-hour OGTT on the other.
Subjects and Methods: We performed CGM at 24-30 weeks in 12 women, age 24-40 years. Three women with GDM (positive 3-hour OGTT) and Fructosamine <198 mM/l. Three women without GDM (normal OGTT) and six non-pregnant women. Diagnosis of GDM was established by abnormal 3-hour OGTT as adopted by current guidelines of ACOG and ADA. Cut off Fructosamine between women with and without GDM was 198 mM/l in a recent study.
Results: Mean diurnal glucose levels with CGM were not significantly different amongst the three groups (GDM, 85-91 mg/dL; No GDM, 80-88 mg/dL; Non-pregnant, 75-94 mg/dL). The normal ranges of glucose (60-140mg/dL) on CGM were not significantly different either amongst all groups. Moreover, not a single glucose level was over 140 mg/dL in any group including women with diagnosis of GDM by 3-hour OGTT and Fructosamine <198 mM/l.
Conclusion: 3-hour OGTT may be false positive as confirmed by both CGM and random Fructosamine level in many pregnant women. Thus, CGM and random serum Fructosamine level are probably more accurate diagnostic tests of GDM in comparison to 3-hour OGTT. However, Fructosamine determination is distinctly more convenient, less expensive, and therefore more acceptable to pregnant women.
