Limitations to body length/serum creatinine ratio as an estimate of glomerular filtration in children

Abstract.

The ability of the Schwartz formula (C _SCH) to estimate glomerular filtration rate (GFR) accurately was investigated in children with renal disease. ¹²⁵Iodine-iothalamate clearance (C _IO) was used as the reference standard for measuring GFR. Data from 176 C _IO studies performed on 133 children (aged between 1 and 18 years) were compared with the simultaneous estimation of GFR by C _SCH. The overestimation of GFR by C _SCH was inversely proportional to the level of renal function. When C _IO was >90 ml/min per 1.73 m², C _SCH overestimated GFR by only 0.1%±3%, but when C _IO was ≤15 ml/min per 1.73 m², C _SCH overestimated GFR by 164%±42%. When renal function is normal or mildly reduced (GFR >50 ml/min per 1.73 m²), C _SCH overestimated C _IO by only 10.3±3.0%, compared with 90.3±14.5% when renal function was moderately to severely curtailed (GFR ≤50 ml/min per 1.73 m²). We conclude that C _SCH is valid in predicting GFR only in children with normal renal function and mild insufficiency.