Reproducibility of a 75G oral glucose tolerance test in pregnant women

Objective: To determine the reproducibility of the oral glucose tolerance test (OGTT). Design: A retrospective study of 205 women who underwent screening for gestational diabetes. Setting: A university teaching hospital in a South African city. Sample: Women who had an abnormal OGTT had the test repeated during the same pregnancy without any diabetic or dietary advice given in the intervening time period. Methods: Women with two OGTTs in the same pregnancy had a proforma completed at the time. Completed proformas were filed and reviewed for the purpose of this study. Main outcome measure: The. statistic was used for estimating the agreement between repeated tests using the same nominal or dichotomous scale. Results: The OGTT was repeated during the index pregnancy in 205 women and in a subset of 76 women within 17 days. The. statistic was 0.269 for 205 women and 0.212 for 76 women for the fasting glucose value (fair strength of agreement). The. statistic for the 2-h glucose value was 0.157 for 205 patients and 0.174 for 76 patients (slight strength of agreement). The overall OGGT classification produced. statistics of 0.167 and 0.150 for the whole group and the 76 patients, respectively. Conclusion: The reproducibility was better with the fasting glucose and less with the 2-h result and the overall OGGT classification. Caution needs to be exercised when interpreting the single positive result of an OGTT in pregnant women.