calculated creatinine clearance min ml measured serum uln days obtained 
creatinine clearance min ml estimated serum uln renal cc measured 
creatinine range serum normal min ml clearance outside renal reference 
creatinine mg clearance min ml dl serum calculated measured estimated 
crcl creatinine min ml clearance calculated serum uln measured renal 
creatinine clearance hour urine min ml collection calculated serum measured 
creatinine normal age patients clearance grade biopsy renal serum prior