Dowling TC, Frye RF, Fraley DS, Matzke GR. Comparison of iothalamate clearance methods for measuring GFR.
Pharmacotherapy 1999;
19:943-50. [PMID:
10453965 DOI:
10.1592/phco.19.11.943.31576]
[Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
STUDY OBJECTIVE
To evaluate the bias and precision of three methods of measuring glomerular filtration rate (GFR) relative to a standard method.
DESIGN
Prospective, outpatient study.
SETTING
University-affiliated general clinical research center.
PATIENTS
Twenty-six patients with various degrees of renal function (GFR range 25-151 ml/min/1.73 m2).
INTERVENTIONS
Each patient received iothalamate twice during the study visit, first as a bolus injection and then as a priming dose followed by a constant-rate infusion for 2.5 hours.
MEASUREMENTS AND MAIN RESULTS
Plasma (ClpIVB) and renal clearances (ClrIVB) after bolus injection and plasma clearance during constant-rate infusion (ClpINF) were compared with standard renal clearance during constant-rate infusion (ClrINF). All three measures were highly correlated with ClrINF (r>0.90, p<0.001). The mean ClrIVB was not significantly different from ClrINF (106.3+/-30.4 vs 104.2+/-28.5 ml/min/1.73 m2) and provided a precise (8.8%, 95% CI 6.5-11.1%) and unbiased measure of GFR. Both ClpIVB and ClpINF were positively biased; values exceeded ClrINF by 11.8+/-11.1 (p=0.0001) and 10.5+/-12.5 ml/min/1.73 m2 (p=0.0003), respectively. Use of a nonrenal correction factor of 9.8 and 10.5 ml/min/1.73 m2 for infusion and bolus plasma clearance values, respectively, eliminated bias and improved the precision of these methods.
CONCLUSIONS
Iothalamate renal clearance after bolus injection is a simple, accurate, and precise measurement of GFR and may be a useful alternative to the standard infusion method in clinical investigations. The corrected plasma clearance provides a simple index of GFR for clinical practice.
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