INACCURACY OF THE SCHWARTZ FORMULA IN ESTIMATING GLOMERULAR-FILTRATION RATE IN NIGERIAN CHILDREN

The accurate estimation of renal function is of vital importance in th e management of a child with renal disease. Given the well known diffi culties of obtaining an accurately timed 24-hour mine sample from chil dren and lacking the resources for estimating glomerular filtration ra te (GFR) using radionuclide methods, the clinician practising in a dev eloping country often has to resort to the use of height/plasma creati nine formulae when a rapid assessment of GFR is needed. In order to as sess the accuracy of one of the better known formulae (Schwartz formul a) in predicting GFR, 34 children with the nephrotic syndrome and 30 a pparently healthy children with no evidence of renal disease were stud ied at the University College Hospital, Ibadan. Two methods, Airman-Bl and analysis and correlation coefficients, were used to assess agreeme nt between measured GFR (by endogenous creatinine clearance) and GFR e stimated by formula. The results show that the height/plasma creatinin e formula of Schwartz st al. is a poor predictor of GFR as measured by endogenous creatinine clearance in Nigerian children and that it over estimated GFR in over two-thirds of the children. These observations m ay be due to differences in the constant, k, in the formula, which was found to vary widely in this study with a mean value of 0.45 compared with 0.55 in the formula. It is suggested that height/creatinine form ulae for predicting GFR be tested and validated for accuracy in a give n environment before routine use in clinical settings.