GIT (Glucose Infusion Test): polycentric evaluation of a new test for vascular access recirculation

Introduction. Vascular access recirculation (AR), which is often unacknowledged, remains an important cause of inadequate dialytic dose. The glucose infusion test (GIT) is a new method for detecting and quantifying AR. This paper reports on a polycentric evaluation of the new test and a comparison with the classical Urea-test (UT). Methods. GIT protocol comprises withdrawal from the arterial port (sample A), injection into the venous drip chamber of 1 g glucose in 4 seconds, withdrawal from the arterial port (sample B) continuously from 13 to 17 seconds. Glucose is determined on A and B by a reflectance photometer. If B = A then there is no recirculation. If B exceeds A by at least 20 mg/dl there is recirculation. AR quantification: AR% = (B-A) / 20. GIT was performed on 623 patients from eleven dialysis centers to screen the patients for AR. Subsequently, GIT and Urea-test (UT) were compared in 189 paired tests. The reproducibility of GIT and UT was studied in 28 paired tests performed in sequence. Results. The screening test by GIT was positive in 68 cases (11 %). The majority of positivities was found in central venous catheters (CVC, 27/50 cases, 54 %), whereas only 7 % of artero-venous fistulas (AVF) were positive. In the CVC group, Tesio catheters were more frequently positive compared to Dual Lumen Catheters (64 % vs. 29 %). The comparison GIT - UT showed that results matched in 162 tests (79 negative and 83 positive both by GIT and UT), showing that on the grounds of UT, GIT has high sensitivity and specificity. In 27 tests GIT was positive, but UT negative. This disagreement is due to the different minimal limit of detection, 1 % for GIT and 5% for UT. The reproducibility was greater with GIT than with UT with a lower D% (respectively -0.6 +/- 2.5 and -0.4 +/- 6.1 %, p<0.001) and a lower coefficient of variation (17 vs 33 %). Conclusions. The screening of 623 patients by GIT confirmed that AR in AVF is normally absent, whereas an un-expectedly high frequency of moderate AR in CVC was found. The GIT-UT comparison showed that the new test is simple and immediate, and gives results with higher accuracy, sensitivity and reproducibility than UT.