Predicting hemorrhage and obstruction in the elderly population using thromboelastographic indices

Qiwen Zheng,^1,* Shuhong Fu,^2,* Dafang Chen,¹ Xiaoxia Li,² Yuru Li,² Yanyan Li,² Jihong Yu,² Meiliang Gong,² Jie Bai<sup>2

1</sup>Department of Epidemiology and Biostatistics, School of Public Health, Peking University Health Science Center, Beijing, People's Republic of China; ²Nanlou Clinical Lab, Chinese PLA General Hospital, Beijing, People's Republic of China

*These authors contributed equally to this work

Objective: To estimate the value of the different thromboelastogram indices for predicting hemorrhage and vascular obstruction in an elderly population.
Methods: This was a prospective cohort study of patients 65 years and older without hematologic disorders who received thromboelastography (TEG) examination at the Chinese People's Liberation Army General Hospital from January 2007 to December 2010. Detailed information was collected at recruitment including their TEG test results. Subjects were then followed during outpatient visits and hospitalization. The primary outcome measures were hemorrhage and vascular obstruction. Receiver-operating characteristics (ROC) curves were used to compare the predictive value of the four TEG indices, reaction time (R), clot formation time (K), maximal amplitude (MA), alpha angle (ANGLE) and their combination for predicting hemorrhage and vascular obstruction. The maximal Youden's index was used to estimate optimal cut-off values for the indices. Areas under the ROC curves were used to estimate overall predictive accuracies.
Results: A total of 403 elderly patients met inclusion criteria and were included: 373 male and 30 females with mean age 83.0 ± 7.3 years and range of 65–103 years. Hemorrhage occurred in 25 (6.2%) patients and vascular obstruction in 78 (19.4%) patients during the 2-year follow up. The currently recommended TEG cut-off values were poorly predictive of vascular obstruction and modestly predictive of hemorrhage. Based on maximal Youden's, the optimal cutoffs of the TEG indices for predicting vascular obstruction were: R = 7, K = 1.5, MA = 63.5, and ANGLE = 67.1. A combination of all four showed the best predictive value (area under the ROC curve of 0.60, sensitivity 85.9%, and specificity 34.7%). The optimal cut-off values for predicting hemorrhage were: R = 7.8, K = 2.3, MA = 50.5, ANGLE = 53.7. A combination of R and MA was also most predictive of hemorrhage (area under ROC curve 0.66, sensitivity 60%, and specificity 71.7%).
Conclusion: The currently adopted cut-off values for TEG indices are poorly and modestly predictive of hemorrhage and obstruction, respectively, in the elderly population. Optimal cut-off values determined by ROC curve analysis improved the prediction of vascular obstruction and hemorrhage.

Keywords: thromboelastography, TEG, elderly, obstruction, hemorrhage, ROC curve, prediction