Estimation of glomerular filtration rate from low-dose injection of iohexol and a single blood sample.

Clearance of a small dose of iohexol (7 g I) was compared with the glomerular filtration rate (GFR) marker 51Cr EDTA in 11 healthy volunteers. The two tracers were injected simultaneously. The plasma concentration of iohexol was measured with x-ray fluorescence technique. Glomerular filtration rate was determined using blood samples drawn three and four hours after injection. An excellent correlation (0.92 less than r less than 0.97) between iohexol clearance and 51Cr EDTA clearance was found. Glomerular filtration rate can be reliably determined with a low dose of iohexol and a single blood sample obtained three hours after the injection in persons with normal serum creatinine. This new method is a good alternative to the methods using radiopharmaceuticals; it causes no radioactive burden to the patients, increases patient comfort, reduces costs, and requires no special license.