SINGLE-SAMPLE METHODS TO MEASURE GFR WITH TECHNETIUM-99M-DTPA

Many single-sample methods have been suggested to simplify the methodo logy of glomerular filtration rate (GFR) measurement. The relative acc uracy of these competing methods is still not clear for Clinical pract ice. Methods: Fifty-four GFR studies with Tc-99m-DTPA were performed o n 37 adult patients (serum creatinine 0.8-10 mg/dl), Each study includ ed a UV/P, plasma clearance method (three-sample) and single-sample me thods. The single-sample methods used were those of Christensen and Gr oth (modified by Watson), Constable, Dakubu, Grath and Aasted, Jacobss an, Morgan, Russell and Tauxe, Results: When the GFR greater than or e qual to 30 mlimin (n = 26), all of the single-sample methods were high ly correlated with UV/P, The correlation of the single-sample method w ith the plasma clearance was higher than with UV/P, In this group (GFR greater than or equal to 30 ml/min), the Groth 4-hr sample method had the best Value of both absolute difference and percent absolute diffe rence(mean +/- s.e. = 11.05 +/- 2.51 ml/min and 14.08% +/- 2.43%, resp ectively), Most single-sample methods do not perform well at GFR < 30 ml/min (n = 28), and none of them has a good correlation with UV/P or plasma clearance at this level of renal function, However, the Groth a nd Aasted's 4-hr sample method was the best compared with others (mean +/- s.e. = 8.43 +/- 1.30 ml/min for absolute difference, and 65.91% /- 16.70% for percent absolute difference), Conclusion: Single-sample methods may not correctly predict GFR in advanced renal failure, Groth and Aasted's method with 4-hr plasma sample has both the lowest mean absolute difference and percent absolute difference in both the group with GFR greater than or equal to 30 ml/min and GFR < 30 ml/min. All m ethods perform acceptably at GFR greater than or equal to 30 ml/min.