A 50-g glucose challenge test: is there any diagnostic cut-off?
OBJECTIVE
To evaluate the diagnostic performance of 50-g glucose challenge test for diagnosis of gestational diabetes.


METHODS
A retrospective study was conducted by reviewing the medical records of pregnant women who had a 50-g glucose challenge test of 140 mg/dL or higher and followed by a 100-g glucose tolerance test. Results were categorized in 10 mg/dL increments. Gestational diabetes was diagnosed using National Diabetes Data Group criteria.


RESULTS
The present study included 2,226 cases from universal screening of 11,084 pregnant women. The incidence of gestational diabetes was 3.2% (351/11,084). Only 1.6% (6/374) of patients with positive screening results of less than 145 mg/dL had gestational diabetes. All of the 6 women undiagnosed by this threshold were gestational diabetes class A1 and had at least one risk factor Of 1,875 women, seven cases (0.4%) would be over diagnosed as gestational diabetes if 100-g glucose tolerance test was not performed after a result of 50-g glucose challenge test of > or = 250 mg/dL (99.6% specificity, 85.8% negative predictive value, 12.3% sensitivity and 86.0% positive predictive value).


CONCLUSIONS
A 50-g glucose challenge test may be used as a diagnostic test when the value is > or = 250 mg/dL. The present data suggested that the value of glucose screening of > or = 145 mg/dL can be used as a threshold for a positive test in the low risk women.
Department of Obstetrics and Gynecology, Bangkok Metropolitan Administration (BMA) Medical College and Vajira Hospital, Bangkok.
Waralak
W
Yamasmit
Surasith
S
Chaithongwongwatthana
Boonchai
B
Uerpairojkit
D000328:Adult; D016640:Diabetes, Gestational / Q000175:diagnosis* / Q000503:physiopathology; D005260:Female; D005865:Gestational Age; D005951:Glucose Tolerance Test; D006801:Humans; D015994:Incidence; D011247:Pregnancy; D012189:Retrospective Studies; D012307:Risk Factors; D012680:Sensitivity and Specificity; D055815:Young Adult