Reassessment of a classical single injection 51Cr-EDTA clearance method for determination of renal function in children and adults. Part II: Empirically determined relationships between total and one-pool clearance.
BACKGROUND
The one-pool or slope-intercept technique is widely used when determining total (51)Cr-EDTA plasma clearance (Cl). The one-pool clearance (Cl(1)), which always exceeds Cl, has mostly been corrected to Cl by multiplication by a constant factor = 0.80, suggested by Chantler (CH(0.80)), or by using a second-order polynomial originally proposed by Brøchner-Mortensen (BM) and later recommended by the British Nuclear Medicine Society (BM(BNMS)). Theoretical considerations indicate that the CH correction gives a systematic overestimate of Cl, whereas the BM correction may underestimate Cl at high values.


OBJECTIVE
To assess the accuracy of Cl as estimated from Cl (1) corrected either by CH(0.80) or by second-order polynomials.


METHODS
Cl(ref) was determined in 149 subjects (M/F/children: 71/46/32) from a complete plasma curve followed for 4-5 h after injection of (51)Cr-EDTA (range of Cl(ref) : 8-183 mL/min/1.73 m(2)). Cl(est) was determined from Cl(1) subsequently corrected by CH(0.80) and four second-order polynomials.


RESULTS
Using CH(0.80) correction, Cl(est) underestimated Cl(ref) (by a maximum of 20%) at Cl(ref) values less than about 100 mL/min/1.73 m(2) in children and 130 mL/min/1.73 m(2) in adults. At higher clearance levels, Cl(ref) was increasingly overestimated. Taking the BM(BNMS) correction as representative of second-order polynomials, Cl(est) increasingly underestimated Cl(ref) at high levels, the error being 10% at a Cl(ref) value of about 175 mL/min/1.73 m(2).


CONCLUSIONS
We suggest that the tested correction equations are replaced by the given common correction equation based on the "true" relationship between Cl(1) and Cl thoroughly described in part I of this study.
Brøchner-Mortensen
Jens
J
Department of Nuclear Medicine and Center for Cardiovascular Research, Aalborg Hospital, Aarhus University Hospital, Aalborg, Denmark.
Jødal
Lars
L
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001830:Body Surface Area; D002648:Child; D002675:Child, Preschool; D004492:Edetic Acid / Q000008:administration & dosage / Q000493:pharmacokinetics*; D005260:Female; D006801:Humans; D007223:Infant; D007267:Injections; D007677:Kidney Function Tests / Q000379:methods*; D008297:Male; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D008954:Models, Biological; D010953:Plasma Volume; D012680:Sensitivity and Specificity; D055815:Young Adult
D004492:Edetic Acid