A prospective comparison of two endogenous creatinine clearance testing methods in hospitalized hypertensive gravid women.

Abstract

Although 24-hour endogenous creatinine clearance testing is common in pregnancies complicated by hypertension, inaccuracies limit its usefulness. We controlled the conditions under which 4-hour endogenous creatinine clearance testing was performed and compared the results with outcomes of 24-hour tests from the same patients. In 83 women hospitalized with mild hypertension in the third trimester, we measured endogenous creatinine clearance with a 4-hour urine collection during lateral recumbency and supervised oral hydration. This test was paired with a 24-hour test performed immediately thereafter. No restrictions or recommendations regarding ambulation or oral intake were imposed for the 24-hour test. The 4-hour endogenous creatinine clearance value exceeded the 24-hour value in 133 of the 136 paired comparisons (p < 0.0001). Results of the tests from only the 29 patients with multiple paired tests showed more similarity (p < 0.005) among the 4-hour than among the 24-hour clearances. The 4-hour endogenous creatinine clearance test, as described, provides a higher and less variable estimate of renal function in hypertensive pregnant women than does the 24-hour test.