Glomerular filtration rate in dogs as estimated via plasma clearance of inulin and iohexol and use of limited-sample methods

Abstract

To compare plasma clearance of inulin and iohexol determined by use of 9 plasma samples for evaluation of glomerular filtration rate in dogs and to evaluate limited-sample approaches for evaluation of plasma clearance of these markers. 43 dogs of various breeds that weighed between 5.5 and 63 kg and that had various degrees of renal function. 9 plasma samples were obtained from each dog at 5 minutes to 6 hours after IV bolus injection of iohexol and inulin. Clearance was calculated by use of results for all 9 samples (ie, reference method). Results for 3 limited-sample strategies for determination of plasma clearance of iohexol and inulin were compared with results for the reference method. Mean clearance of inulin and iohexol for the reference method was 2.72 and 2.48 mL/min/kg, respectively. The mean difference between clearance of these 2 markers for the reference method was 0.24 mL/min/kg. In general, use of the limited-sample strategies yielded clearance values similar to those for the reference method. More accurate estimates of clearance were obtained for iohexol than for inulin by use of the limited-sample methods. Use of iohexol and inulin yielded similar but not identical results for plasma clearance. Accuracy for limited-sample methods would be acceptable for many clinical and research situations.