Comparison of two methods for the evaluation of renal perfusion

The validity of a single blood sample technique at the 44th min after the injection of OIH for the evaluation of effective renal plasma flow was assessed by comparison with a standard clearance method, based on two-compartment analysis of plasma disappearance of the tracer. The simplified method tended to overestimate the true values; the 95% confidence interval for the error in predicting the true value was found to be +/- 88 ml/min. Overall, the simplified method appears to be adequate to study renal perfusion or its changes in different conditions, but due to the predicting error it requires a larger number of patients, as compared with the reference method, in order to obtain statistically valid results.