The Oral Glucose Tolerance Test: Changed Results Using Different Drinking Solutions?

The impact of different drinking solutions used for an oral glucose tolerance test (oGTT) on 2-h glucose values and gastrointestinal side effects are not clear. This study compared a commercially produced solution (Accu-Chek Roche solution) and a standardized pharmacy solution (NRF 13.8. oGTT solution) within the German National Cohort (NAKO), including the assessment of gastrointestinal symptoms.The Accu-Chek Roche solution comprises mono- and oligosaccharides with blackcurrant juice for enhanced flavor. The NRF 13.8. oGTT solution contained glucose monohydrates only, with citric acid to maintain the pH for preservation, and did not include flavor enhancers. Within a subgroup of the NAKO participants obtaining a standardized 75g oGTT, 818 participants each received the Accu-Chek Roche solution and the NRF 13.8. oGTT solution matched by study center, sex, age, body mass index, and fasting glucose values. Intra-class correlations for 2-h glucose values were calculated and agreement evaluated with Bland-Altman plots; additionally, coefficients of variation and their difference were estimated for the two solutions.The mean difference of the 2-h glucose concentrations between the Accu-Chek Roche and NRF 13.8. oGTT solution was - 3.4 [95% CI - 6.1; - 0.9] mg/dL. The Bland-Altman plot showed increasing variability of differences with increasing 2-h glucose concentrations without a systematic pattern. The intra-class correlations of 2-h glucose values within matched pairs were 22% [95%CI: 16%; 29%]. The coefficients of variation for 2-h glucose observed with the Accu-Chek Roche and NRF 13.8. oGTT solutions were 25% [24%; 27%] and 25% [23%; 26%], respectively, with a difference of 1% [- 1%; 3%]. Nausea or vomiting were observed in<0.1% of matched participants with no differences between the solutions.The differences in 2-h glucose values and frequency of acute gastrointestinal side effects were not clinically different in participants following the consumption of the Accu-Chek Roche or the NRF 13.8. oGTT solutions.