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24-10-2011 | Cardiology | Article

Thromboelastography reference ranges unsuitable for pregnant women


Free abstract

MedWire News: The use of standard reference ranges for thromboelastography parameters may not be suitable for pregnant women, and could lead to the misinterpretation of the coagulation state, Czech researchers report.

Coagulation levels in pregnant women are routinely compared with the reference ranges for the general population, even though it is common knowledge that coagulation changes towards hypercoagulation during pregnancy, explain Ferdinand Polak (Charles University, Prague) and colleagues.

Thromboelastography is one method that can be used to examine blood coagulation.

To investigate whether it is accurate to use the same reference ranges for thromboelastography examinations in pregnant women as those used for the general population, Polak and team compared 60 healthy women in their third trimester of pregnancy with 43 similar-aged healthy nonpregnant women. They performed thromboelastography on venous blood samples taken from each of the women.

Of note, all of the pregnant women subsequently delivered without any thrombotic or inadequate bleeding complications.

The researchers report that there were significant differences between the pregnant and nonpregnant women in all thromboelastography parameters, with pregnant women showing a tendency for hypercoagulation.

More specifically, R (time from initiation of the test to the initial fibrin formation) was 4.7 minutes in pregnant women, compared with 7.8 minutes in nonpregnant women, while the respective values for k (time from beginning of clot formation until the amplitude of thromboelastogram reaches 20 mm) were 1.5 and 2.7 minutes.

The alpha angle, maximum amplitude (MA), coagulation index, and LYS60 (the rate of amplitude reduction 60 min after MA) were 69.9°, 71.3 mm, 2.7, and 1.1%, respectively in pregnant women, compared with 54.4°, 63.1 mm, -1.9, and 4.8% in nonpregnant women.

Because the differences between the groups were statistically significant, the researchers determined new thromboelastography reference limits for pregnant women for each of the parameters.

These were 2-8 minutes for R (normally 4-8 minutes), 1-3 minutes for k (normally (1-4 minutes), 60-77° for alpha angle (normally 47-74°), 64-76 mm for MA (normally 55-73 mm), 0-5.0 for coagulation index (normally -3.0-3.0), 0-3% for LYS60 (normally 0-15%).

"In our opinion, the use of these new standards will allow a more accurate interpretation of coagulopathies during pregnancy," Polak and co-authors conclude in the journal Thrombosis Research.

MedWire ( is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2010

By Laura Dean

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