This review and opinion article focuses on the definitions and meanings of abnormal protein excretion in pregnancy, asking the following questions: Are our tests to determine abnormal proteinuria adequately performed? Are current guidelines for diagnosis of excessive proteinuria, especially when used to identify preeclampsia, supported by adequate data? Can the magnitude of proteinuria be used as a reliable clinical biomarker of the gravity of preeclampsia? Should timed urine collections, primarily 24-hour excretions, be supplanted by the urine protein/creatinine ratio in clinical practice? The answers to most of these questions are: We are not sure, or some guidelines are poorly supported by data and may prove erroneous. We suggest a more physiologic approach to assessment of proteinuria and believe that if clinicians and investigators looked at proteinuria in terms of how the kidney handles protein in health and disease it would lead to a more rational and evidence-based approach to proteinuria in pregnancy. Finally, we recommend that current cutoff for abnormal proteinuria be used to diagnose preeclampsia, but the level of proteinuria should not guide management. Other variables, such as status of blood pressure control, evidence of increasing organ damage in the liver and hematological systems, evidence of falling glomerular filtration rate, and signs of neurological involvement, are more reliable indicators of severity of preeclampsia.
Interpreting the meaning of excess proteinuria requires an understanding of how filtered and secreted proteins are handled by the kidney in health and disease.
From the Departments of Obstetrics and Gynecology and Medicine, The University of Chicago, Chicago, Illinois.
Continuing medical education for this article is available at http://links.lww.com/AOG/A149.
Corresponding author: Marshall D. Lindheimer, MD, Professor Emeritus, The University of Chicago, Department of Obstetrics and Gynecology and Medicine, 5807 South Dorchester Avenue, Apartment 5E, Chicago, IL; e-mail: firstname.lastname@example.org.
Financial Disclosure: The authors did not report any potential conflicts of interest.