Retrograde versus antegrade cannulation in the intravenous glucose tolerance test

To investigate whether drawing blood from a retrogradely cannulated hand vein rather than an antegradely cannulated arm vein improves reproducibility in the intravenous tolerance test (IVGTT) we compared these two methods directly by drawing blood from the two sites on the same arm simultaneously. We found no difference in intrasubject coefficients of variation for the measurement of insulin response to glucose (21.5% vs. 22.5%) or insulin sensitivity (22.8 vs. 24.7%) for these two methods. However, the values for insulin response to glucose were significantly increased when blood was drawn from the hand site (410.1 vs. 328.7 pM, P < 0.05). In addition, the failure rate for studies using the retrogradely cannulated hand vein was significantly increased (5% of arm veins vs. 20% of hand veins cannulated, P < 0.05) particularly in female subjects. In conclusion, drawing blood samples from a retrogradely cannulated hand vein appears to have no effect on the reproducibility of the intravenous glucose tolerance test. The acute insulin response to glucose obtained from samples drawn in this manner is, however, significantly increased and this should be borne in mind when comparing results from centers using these different methods.