Evaluation of a single sampling method for estimation of plasma iohexol clearance in dogs and cats with various kidney functions.

Plasma iohexol clearance (PCio) is a practical method for measuring the glomerular filtration rate (GFR) in clinical settings. However, it is too time-consuming for routine application and requires hospitalization for at least half a day. Therefore, the development of a simpler procedure for plasma clearance is necessary to allow the frequent measurement of GFR in clinical settings. The purpose of the present study was to evaluate a single sampling method for estimation of PCio in dogs and cats with various kidney functions. The PCio determined by the 1-compartment model using 3 samples (PCio (3samples)) was used as a reference for the evaluation of the single sampling method (PCio (single)). Plasma iohexol concentration was determined by a cerium arsenite colorimetric method. PCio single was calculated using the equation obtained by nonlinear regression analysis. PCio (single) was significantly correlated with PCio (3samples) in both dogs and cats (dogs: R(2)=0.985, P<0.001, cats: R(2)=0.986, P<0.001). In a receiver operating characteristics analysis, the area under the curve, sensitivity, and specificity for detecting decreased GFR were 0.995 [SE, 0.003], 98%, and 93% for dogs and 0.993 [SE, 0.003], 98%, and 93% for cats, respectively. These results demonstrate that PCio (single) may be very useful for the detection of decreasing GFR in dogs and cats.