Influence of test interval length on the variability of glycemic response tests

The aim of this study was to investigate whether the washout length between glycemic response tests influences their reliability. A total of 3 men and 12 women performed eight identical blood glucose tolerance tests: four tests on consecutive days (short interval) and four tests spread over 20–30 days, with 5–10 days between the tests (long interval). No difference was observed in the coefficient of variation ( P =0.32) of the incremental area under the blood glucose response curve between the short and long interval, and there was no drift within the short ( P =089) and long interval ( P =0.20). The first test did not differ from any of the subsequent tests ( P >0.99). In conclusion, glycemic response testing on consecutive days does not seem to influence the variability of glycemic response tests compared with longer intervals and it does not cause any data drift under conditions of earlier diet and habitual exercise control. In addition, familiarization trials do not seem to be necessary for glycemic response tests.