Clinical limitations of the estimation of glomerular filtration rate from height/plasma creatinine ratio: a comparison with simultaneous 51Cr edetic acid slope clearance.

A retrospective comparison of single determinations of glomerular filtration rate measured by 51chromium-edetic acid slope clearance (CEDTA) and height/plasma creatinine ratio (Ht/PC) was undertaken in 199 children aged between 3 and 16 years. Analysis of the data indicated that only if Ht/PC less than or equal to 1.2 cm/mumol per 1 was the relationship between Ht/PC and CEDTA linear. Over this range where renal function is significantly impaired the confidence limits for individual prediction of glomerular filtration rate were so wide that a definitive measurement of renal function would be necessary in clinical practice. Where Ht/PC greater than or equal to 1.2 the relationship was non-linear and the predictive confidence limits very wide. To apply the technique as a screening test for normal renal function (CEDTA greater than or equal to 80 ml/min per 1.73 m2) the Ht/PC would need to exceed 2.16. In our study this would have detected 57 out of 131 patients who had normal glomerular filtration rates and erroneously included 2 out of 68 with subnormal renal function.