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Blood coagulation testing of pregnant women with hypertension can be reduced

High blood pressure or hypertension complicates 6 to 10 percent of pregnancies and can lead to a serious condition called preeclampsia. Preeclampsia may cause abnormal liver function, compromised kidney function, swelling due to fluid retention, alterations of electrolyte and fluid balance, and blood clotting deficiencies that put a pregnant woman at serious risk of hemorrhage. Severe preeclampsia can threaten the life of the mother and her baby.

Doctors often use several relatively expensive blood coagulation tests to diagnose preeclampsia in pregnant women with hypertension: prothrombin time (PT), partial thromboplastin time (aPTT), fibrinogen levels, or a combination of these tests. However, a normal blood platelet count plus a normal lactate dehydrogenase test can predict coagulation abnormalities and obviate the need for additional tests. This is true especially if there is no evidence of bleeding or other condition that could reduce the blood's ability to clot (coagulopathy), concludes a study supported by the Agency for Health Care Policy and Research (HS08131).

Researchers led by William M. Barron, M.D., of Loyola University Medical Center, searched laboratory records and charts at two Chicago academic medical centers for patients admitted between May and November 1993. They identified pregnant women tested for hypertension and then excluded conditions producing coagulopathy. Preliminary data on 73 women found that platelet count plus a lactate dehydrogenase test best predicted coagulation abnormalities.

Among the 30 percent of another 732 women who underwent additional coagulation tests, few had abnormal results, and very few had levels denoting significant risk of hemorrhage. The combination of a normal platelet count plus a normal lactate dehydrogenase test was able to predict no clinically significant abnormalities of PT and aPTT 100 percent of the time and no significant abnormalities of fibrinogen 99 percent of the time. These findings support published practice guidelines, none of which call for routine use of PT, aPTT, or fibrinogen in evaluation of women with hypertension complicating pregnancy.

More details are in "Reducing unnecessary coagulation testing in hypertensive disorders of pregnancy," by Dr. Barron, Paul Heckerling, M.D., Judith Hibbard, M.D., and Susan Fisher, Ph.D., in the September 1999 Obstetrics and Gynecology 94(3), pp. 364-370.

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