REPRODUCIBILITY OF THE FIRST-PHASE INSULIN-RESPONSE TO INTRAVENOUS GLUCOSE IS NOT IMPROVED BY RETROGRADE CANNULATION AND ARTERIALIZATION ORTHE USE OF A LOWER GLUCOSE DOSE

OBJECTIVE - To determine whether the reproducibility of the first-phas e insulin response (FPIR) measured during an intravenous glucose toler ance rest is improved by the use oi a lower glucose dose or retrograde sampling from an arterialized hand vein. RESEARCH DESIGN AND METHODS - Previous studies have suggested that the high within-subject variati on of FPIR measurement of up to 110% could be reduced by sampling from a retrograde cannulated and arterialized hand vein opposite to the cu bital fossa vein through which the glucose was injected or by the use of a lower dose of glucose. Two low-dose (glucose, g/m(2) injected ove r 30 s) and two standard Islet Cell Antibody Registry Users Study (ICA RUS) (glucose, 0.5 g/kg injected over 3 min) tests were performed on s even normal subjects at 2-week intervals. Samples were collected simul taneously from the cubital fossa vein, through which the glucose was i njected, and from a retrograde cannulated, contralateral hand vein tha t was arterialiled by heating. FPIR was expressed as the sum of the in sulin measurements 1 and 3 min after the completion of the glucose inj ection and as the area under the insulin curve between 0 and 10 min.RE SULTS - Responses to the mean sum serum serum insulin concentrations a t 1 and 3 min after intravenous glucose were significantly Lower for t he low-dose test (mean 94 mU/l) than for the high-dose test (mean 184 mU/l) for samples taken from the arm (P < 0.05); mean 0- to l0-min ins ulin areas were 367 and 596 mU/l for low- and high-dose tests, respect ively (P < 0.05). Within-subject coefficients of variation for samples from the hand or the arm ranged from 0.33 to 17.5% and 1.3 to 38% for successive ICARUS and low-dose tests, respectively. Reproducibility, measured by the coefficient of variation between successive tests for each protocol, was not significantly different using samples taken Fro m the arm or the contralateral hand. CONCLUSIONS - The intravenous glu cose tolerance test is reproducible when performed by the same operato r over a short rime span. Reproducibility is not significantly improve d by sampling from an arterialized, retrograde cannulated, contralater al hand vein. There is no case for changing the present ICARUS protoco l to incorporate retrograde cannulation or low-dose (5 g/m(2)) glucose .