Racial differences in oral glucose screening test results: establishing race-specific criteria for abnormality in pregnancy.

OBJECTIVE: To determine whether the 1-hour glucose screening test threshold of 140 mg/dL yields similar results in identifying gravidas with gestational diabetes mellitus in different races and, if not, to establish consistent race-specific thresholds.
METHODS: Nine hundred twenty-one gravidas undergoing routine third-trimester glucose screening were categorized as white, black, Asian, or Filipino. Mean (+/- standard deviation) glucose screening test values, the proportions with results exceeding 140 mg/dL, and the positive predictive values for gestational diabetes mellitus were calculated by race. Race-specific thresholds were calculated by standardizing the percentile rank cutoff for test results in each group.
RESULTS: Mean glucose screening test results differed significantly by race: blacks 116.4 +/- 31.6 mg/dL, whites 123.2 +/- 28.4 mg/dL, Filipinos 127.6 +/- 26.3 mg/dL, and Asians 134.7 +/- 25.0 mg/dL (P < .001). No significant difference was found between Hispanic and non-Hispanic whites (123.2 +/- 28.3 versus 123.5 +/- 28.5 mg/dL). Significant different proportions of gravidas exceeded the 140-mg/dL threshold by race: blacks 17.5%, whites 27.4%, Filipinos 31.3%, and Asians 40.6%. The proportions with results above 140 mg/dL who had abnormal 3-hour glucose tolerance tests also varied markedly by race: blacks 42.9%, whites 17.3%, Filipinos 11.5%, and Asians 11.5%. Adjusted screening test thresholds, calculated for each race to establish consistency of the screening test, were 130 mg/dL for blacks, 140 mg/dL for whites, 145 mg/dL for Filipinos, and 150 mg/dL for Asians.
CONCLUSION: Race-specific glucose screening test thresholds should be used to ensure consistency in properly identifying gravidas at risk for gestational diabetes mellitus.