INACCURACY OF GLOMERULAR-FILTRATION RATE ESTIMATION FROM HEIGHT PLASMA CREATININE RATIO/

Use of a height/plasma creatinine formula to estimate glomerular filtr ation rate (GFR) is simpler and less invasive than renal or plasma cle arance methods. The aim of this study was to determine whether these f ormulas enabled accurate prediction of GFR measured from the plasma cl earance of Cr-51 labelled ethylene-diaminetetra-acetic acid (Cr-51-EDT A). Thirty nine patients underwent GFR measurement at least six months after potentially nephrotoxic chemotherapy. Altman-Bland analysis was performed on the measured GFR and that estimated simultaneously using the original and a modified Counahan-Barratt formula and the Schwartz formula. The limits of agreement of the estimated GFR with the measur ed GFR were unacceptably wide in each case, despite highly significant correlation coefficients, The bias was smallest for the modified Coun ahan-Barratt formula. Use of these formulas to estimate GFR in childre n is insufficiently accurate for research purposes and has limitations in clinical practice. Furthermore, use of correlation coefficients to evaluate different methods of measuring GFR is inappropriate.