Pitfalls in measuring inulin and para-amino-hippuric acid clearances.

Various carbohydrates and a variety of widely used medicines interfere with the generally used laboratory methods for determining inulin and para-aminohippuric acid (PAH). When these pitfalls are not recognized, false measurements of inulin and PAH clearances, which represent glomerular filtration rate and renal plasma flow respectively, are obtained. When performing these tests a careful history of dietary habits and oral drug therapy must be taken.