Chromium-51-EDTA clearance in adults with a single-plasma sample.
In 1996, a committee on renal clearance recommended a mean sojourn time-based methodology for single-sample determination of plasma clearance of 99mTc-diethylenetriamine pentaacetic acid (DTPA) to be used on adults if the patient's glomerular filtration rate (GFR) is suspected to be >30 ml/min. The main purpose of this study was to derive a mean sojourn time-based formula for calculation of 51Cr-ethylenediamine tetraacetic acid (EDTA) clearance in adults.


METHODS
Two groups of patients with 51Cr-EDTA clearance (Cl) between 16 and 172 ml/min were studied. In Group I (n = 46), reference Cl was determined as a multiplasma sample, single-injection method (ClSM). Sixteen blood samples were drawn from 0 until 5 hr after a single intravenous injection of 51Cr-EDTA. In Group II (n = 1046), reference Cl was determined by the Brøchner-Mortensen four-sample clearance method (ClBM). The plasma time-activity curves of Group I were used to derive two mean sojourn time-based formulas (Formulas 1 and 2) for calculation of a single-sample clearance. Formula 1 was derived from the entire time-activity curve, whereas the derivation of Formula 2 used only the final slope of the time-activity curve. The accuracy of the two formulas and the Christensen and Groth 99mTc-DTPA formula was tested on Group II.


RESULTS
Chromium-51-EDTA Cl calculated by Formula 1 was almost identical to the Cl calculated by the reference Cl method (r = 0.982; SDdiff = 5.82 ml/min). Both 51Cr-EDTA Cl calculated by Formula 2 and by the 99mTc-DTPA formula showed close correlation with the reference method (r = 0.976, r = 0.985, respectively) but systematically overestimated GFR for the whole range of clearance values by 3.5 and 3.2 ml/min (p<0.001), respectively.


CONCLUSIONS
It is possible to get an accurate determination of 51Cr-EDTA Cl from a single-plasma sample in adults by the mean sojourn time methodology. The determination is marginally more accurate (p<0.001) if using a formula derived from the entire plasma time-activity curve than from only the final slope. The single-sample formula derived for determination of 99mTc-DTPA Cl tends slightly to overestimate GFR if used to calculate 51Cr-EDTA Cl.
Mårtensson
J
J
Department of Clinical Physiology, Norrlands University Hospital, Umeå, Sweden.
Groth
S
S
Rehling
M
M
Gref
M
M
D000328:Adult; D000367:Age Factors; D000368:Aged; D001830:Body Surface Area; D002860:Chromium Radioisotopes / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D004492:Edetic Acid / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D005919:Glomerular Filtration Rate; D006801:Humans; D007275:Injections, Intravenous; D007668:Kidney / Q000502:physiology*; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D008954:Models, Biological; D019275:Radiopharmaceuticals / Q000097:blood / Q000493:pharmacokinetics; D012044:Regression Analysis; D015203:Reproducibility of Results; D016284:Technetium Tc 99m Pentetate / Q000097:blood / Q000493:pharmacokinetics; D013997:Time Factors
D002860:Chromium Radioisotopes; D019275:Radiopharmaceuticals; D004492:Edetic Acid; D016284:Technetium Tc 99m Pentetate