Establishing a normal reference range for thromboelastography in North Indian healthy volunteers

Abstract

Background: Thromboelastography (TEG) is relatively recent assay to analyze the coagulation state of a blood sample, providing a continuous visualization of physical changes occurring during blood coagulation. There is a paucity of published literature on assessment of coagulation status using TEG in Indian population.

Aim: The primary aim of the following study is to establish normal reference values for TEG in North Indian healthy volunteers and secondary aim is to compare them with conventional plasma-based routine coagulation tests and the manufacturers reference range.

Materials and methods: A total of 200 healthy volunteers comprised of 100 males and 100 females of age groups between 20 and 50 years, were enrolled over a period of 1 year, i.e., 2011-2012. Thromboelastometry (TEM) was performed on TEM-A automated thromboelastometer (Framar Biomedica, Rome, Italy), using whole blood non-additive (360 µl). TEG parameters analyzed were r-time, k-time, α-angle, maximal amplitude (MA). Prothrombin time (PT), activated partial thromboplastin time (aPTT) and platelet count was performed for all volunteers. The 95% reference range was calculated as (mean-1.96 standard deviation [SD]) to (mean + 1.96 SD).

Results: Our reference values for 95% of 200 volunteers were r-time: 1.8-14.2 min, k-time: 0.7-7.3 min, α-angle: 27.3-72.3° and MA: 32.1-87.9 mm. Maximum clot strength was higher in women compared with men, however statistically insignificant. Overall 14.5% (29/200) of the volunteers had at least one abnormal parameter while 74% (149/200) had deranged TEG values using the manufacturer's reference range. Statistically significant variation was seen in r-time for 84.8% (P < 0.001), for k-time, in 87.1% (P < 0.001), for α-angle in 83.7% (P < 0.001) and for MA in 84% (P < 0.001), between the manufacturer and our reference range.

Conclusion: The efficacy of classical coagulation test has been well-established; on the contrary TEG is a fairly recent assay and its utility for patient management remains to be demonstrated. We observed TEG to be oversensitive in determining coagulopathy where there is no clinical presentation. The manufacturer's reference values may not be appropriate for different ethnicity. TEG may give an overall representation of hemostasis; however, it cannot replace the conventional coagulation tests. We recommend the determination of normal TEG values by each laboratory for their target population.