OI‐B‐2

AIMS Assessment of renal function in pregnancy currently requires a 24‐hour urine creatinine clearance (CrCl). This study compared the Cockcroft & Gault estimation with the measured CrCl in pregnant women. The 24‐hour CrCl was also compared to shorter collection intervals. METHODS This is a prospective, cohort study of pregnant women admitted to the antepartum service at Northwestern Memorial Hospital. Urine was collected in 3 sequential intervals: 2, 6 and 16 hours. Data included: height, weight, age, ethnicity, obstetrical and medical history and serum creatinine. A 24‐hour measured CrCl was calculated from the pooled collections and using Pearson's correlation compared to the Cockcroft & Gault estimation using ideal body weight and actual body weight. Using ANOVA, the 24‐hour CrCl was also compared to the clearances in the shorter collections. RESULTS Of the 71 women enrolled, 63 completed the study. The calculated CrCl using actual body weight was a better approximation for measured CrCl than ideal body weight (r = .738 and .591, respectively, P=0.01). Substituting a correction factor of .8 rather than .85 in the formula with actual body weight improved the percentage of women with estimated clearances within 20% of measured (70.4% vs 46%). The 2‐hour collection significantly overestimated CrCl compared to the other collection intervals (P=0.001). CONCLUSIONS The Cockcroft & Gault calculation using actual body weight and a correction factor of .8 reliably estimates CrCl in the pregnant patient. Clinical Pharmacology & Therapeutics (2005) 79 , P2–P2; doi: 10.1016/j.clpt.2005.12.007