Endogenous creatinine clearance during pregnancy. II. Variations in normal standards based on methodology

A comparison of the endogenous creatinine clearance (ECC) values by using creatinine levels measured by the autoanalyzer and the modified Jaffe reaction using Lloyd's reagent was performed in 108 normal ambulatory pregnant women at various stages of gestation. The mean ECC was found to be significantly lower when the former method was employed except between 39 and 41 weeks when the values became similar. The mean ECC when calculated from the autoanalyzer results did not vary during pregnancy since serum creatinine by this method remained fairly constant. The difference in serum creatinine level between the two methods observed during pregnancy was absent in the nonpregnant state.