Iothalamate clearance

Pigure 24-9 Relationship between GFR measured using l-iothalamate clearance and estimates of creatinine clearance (CrC ) obtained using the (A) Cockcroft and Gault equation and (B) measured creatinine clearance. (From Coresh JJoto RD, Kirk KA,Whelton PK, Massry S, Jones C, et at. Creatinine clearance os a measure of GFR in screenees for the African-American study of kidney disease and hypertension pilot study. Am J Kidney D/s 1998 32 32-42.)... 

They observed that the MDRD equation provided more accurate assessment of GFR than either the Cockcroft and Gault equation or measured creatinine clearance. The MDRD formula has several advantages (1) it was developed and validated in a large population, (2) it was developed with a population that included both European-Americans and African-Americans, (3) it does not require patient weight, (4) it was validated against an iothalamate clearance estimate... 

Bajaj G, Alexander SR, Browne R, et al. lodine-iothalamate clearance in children. A simple method to measnre glomerular filtration. Pediatr Nephrol 1996 10 25-28. 

Goates JJ, Morton KA, Whooten WW, Greenberg HE, Datz EL, Handy JE, Scuderi AJ, Haakenstad AO, and RE Lynch (1990). Comparison of methods for calculating glomerular filtration rate technetium-99m-DTPA scintigraphic analysis, protein-free and whole-plasma clearance of technetium-99m-DTPA and iodine-125-iothalamate clearance. Journal of Nuclear Medicine 31 424-429. 

Labeling of iodinated aromatics with radioactive or has proved to be a valuable approach to measure GFR in nuclear medicine. Prominent among these is sodium iothalamate, which is specifically marketed in the US for GFR measurement by the name Glofil . Studies have shown that the clearance of this marker by the glomeruli is reproducible, simple, reliable and accurate, especially in children and those with advanced renal diseases [234]. This marker can also be administered by subcutaneous infusion to obtain GFR values without the need for urine collection [235]. Since very low doses (nanomolar scale) of radioactive aromatics are administered, monitoring of renal function may be achieved without disruption of normal physiologic functions. Concerns over radioactivity and associated handling costs may prevent the use of these compounds for routine GFR measurements. 

Radiopharmaceuticals that have been used include (1) Cr-(2) Tc-diethylenetriaminepentaacetic acid (DTPA), and (3) I-iothalamate. Cr-EDTA is preferred to 99mgamma camera imaging. T-iothalamate is no longer approved for intravascular use in some countries. GFR measurements may be based on either the urinary or plasma clearance of the marker. To ensure accuracy when measuring GFR using urinary clearance methods it is essential that (1) renal... 

Rohn HA, Hall PM, Wei R. Inaccuracy of estimated creatinine clearance for prediction of iothalamate glomerular filtration rate. Am J Kidney Dis 1984 9 48-54. 

Formal measures of glomerular filtration rate (GFR), using intravenous inulin or radio-iodinated sodium iothalamate, will not have been performed on most patients with relative renal failure in ordinary clinical practice. Of several alternatives in adults, creatinine (Cr) clearance (CrCL) is probably the most commonly employed, and uses the familiar formula ... 

Cross-sectional studies demonstrate decreased GFR as a function of age when GFR is measured as inulin, iothalamate, or creatinine clearance. The Baltimore Longitudinal Study on Aging, an evaluation of 254 normal healthy subjects, revealed that creatinine clearance decreases at the rate of approximately 0.75 mL/min per 1.73 m per year beginning at the fourth decade of life. These subjects were evaluated prospectively for up to 23 years. Interestingly, approximately one-third of the subjects showed no change in renal function from their baseline value, and a small number showed an increased clearance. These changes may be due to normal physio-... 

ESKD (see Chap. 44), necessitating dialysis or transplantation for survival (see Chaps. 45 and 87). The rate of progression can be slowed and in some cases halted through dietary modification and blood pressure control, angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker therapy, and improved glucose control in patients with type I diabetes mellitus (see Chap. 43). The efficacy of these interventions is optimally assessed with serial measurements of accurate and sensitive indices of GFR such as iohexol, iothalamate, or radioisotope clearances. ... 

Maher FT, Nolan NG, Elverback LR. Comparison of simultaneous clearances of 1251-labeled sodium iothalamate and of inulin. Mayo Clin Proc 1971 46 690-691. 

The gold standard for measuring GFR is by monitoring the renal clearance of an ideal filtration marker, such as inulin, iothalamate, or iohexol. Renal clearance is calculated as follows ... 

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