Rounding of low serum creatinine levels and consequent impact on accuracy of bedside estimates of renal function in cancer patients.
To compare glomerular filtration rate measured by technetium-99m ([Tc(99m)]) DTPA clearance with estimated creatinine clearance (CrCl) (Cockcroft and Gault (C&G) method) in patients with serum creatinine (Scr) levels <0.06 mmol l(-1), and determine the effect of rounding serum creatinine to 0.06 mmol l(-1). Patients with serum creatinine values <0.06 mmol l(-1) at the time of [Tc(99m)] clearance determination were identified. Creatinine clearance was calculated by the C&G method using both actual and rounded Scr values. A total of 419 adults had GFR measured by technetium-99m diethyl triamine penta-acetic acid ([Tc(99m)] DTPA) clearance. Out of this group, 26 patients had a serum creatinine value <0.06 mmol l(-1). The C&G estimates of renal function using actual serum creatinine resulted in an overall overestimation of 12.9% when compared to [Tc(99m)] DTPA clearance. When the value of serum creatinine was rounded to 0.06 mmol l(-1), the formula underestimated renal function by -7.0%. Analysis of estimated creatinine clearance for different levels of renal function showed significant differences to [Tc(99m)] DTPA clearance. Rounding up of serum creatinine to 0.06 mmol l(-1) improved the predictive ability of the C&G method for the patients with [Tc(99m)] DTPA clearance </=100 ml min(-1), but worsened the effect in those >100 ml min(-1). This work indicates that when bedside estimates of renal function are calculated using the C&G formula actual Scr should be used first to estimate CrCl. If the resultant CrCl is </=100 ml min(-1), then the Scr should be rounded up to 0.06 mmol l(-1) and CrCl recalculated. Further assessment of this approach is warranted in a larger cohort of patients.
Pharmacy Department, Peter MacCallum Cancer Centre, St Andrew's Place, East Melbourne 3002, Australia. Michael.Dooley@petermac.org
M J
MJ
Dooley
S
S
Singh
D
D
Rischin
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003404:Creatinine / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007677:Kidney Function Tests; D008297:Male; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D009369:Neoplasms / Q000097:blood / Q000000981:diagnostic imaging / Q000503:physiopathology*; D011237:Predictive Value of Tests; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics*; D012189:Retrospective Studies; D012307:Risk Factors; D012680:Sensitivity and Specificity; D016284:Technetium Tc 99m Pentetate / Q000493:pharmacokinetics*
D019275:Radiopharmaceuticals; D003404:Creatinine; D016284:Technetium Tc 99m Pentetate