Can we predict excessive bleeding using point‐of‐care assays?

Sir, We read with great interest the recently published review article by Chandler [1]. We agree with author that emergency assessment of hemostasis requires short turnaround time as slow testing may be of no clinical benefit [1]. Our working group has experience with the use of viscoelastic global hemostasis assay such as rotational thromboelastometry (TEM) [2] as well as with use of multiple electrode aggregometry (MEA) [3]. In contrast to Chandler [1], our recently published results suggest the evidence that platelet function testing might be useful for preoperative bleeding risk assessment and/or diagnosing the cause of acquire bleeding syndromes [2,3]. Herein, we will provide some recent literature evidence confirming our hypothesis. Ranucci et co-workers performed a retrospective analysis of prospectively collected data on cardiosurgical patients who were preoperatively exposed to thienopyridine treatment [4]. The authors concluded that the adenosine diphosphate (ADP) test value was associated with postoperative bleeding and platelet transfusion and provided an accurate preoperative prediction of postoperative bleeding [4]. Recently, we conducted prospective observational study with aim to elucidate the possibility of bleeding prediction in patients undergoing coronary artery surgery (CAS) [3]. Aspirin sensitive (ASPI test, P = 0.014) and thienopyridines sensitive (ADP test, P = 0.003) platelet function test values significantly correlated with the extent of chest tube output [3]. Using the receiver operating curve analysis [5], we defined both ASPI and ADP test cutoff values that delineated bleeding tendency [3]. Such a prospective observational trial allowed us to preoperatively stratify patients according to bleeding risk [3]. In addition, Mahla and co-workers [6] reported that a strategy based on preoperative platelet function testing to determine the timing of CAS in clopidogrel-treated patients was associated with the same amount of bleeding observed in clopidogrel-naive patients and 50% shorter waiting time than recommended in the current guidelines [7]. Therefore, recommendations on empiric preoperative antiplatelet medication adjustments, not based on laboratory assessment of platelet function, might be obsolete and could probably be changed as there is growing recent evidence supporting the fact that platelet function testing is useful in predicting bleeding outcomes [2–4,8]. However, further research in this field is required as not all studies investigating this issue reported positive findings, thus lacking strong evidence and clear recommendations with precise cutoffs that would be reliably used in everyday practice. Furthermore, different study settings, and different assays used, as well as different definitions of excessive bleeding and transfusion outcomes hamper definitive conclusions on relationship between point-of-care testing findings and bleeding extent. Noteworthy, disturbances of coagulation consequent to cardiopulmonary bypass (CPB) in cardiosurgical patients have multifactorial etiology, such as loss of platelet reactivity, coagulation factor consumption, hemodilution due to CPB priming procedure, etc. [2]. Therefore, intraoperative use of point-of-care devices to predict excessive bleeding deems reasonable, providing even more accurate assessment of hemostatic disorder by accounting the role of preoperative platelet inhibitors intake, the role of CPB as well as surgical stress on blood hemostatic properties. Intra-operative assessment of hemostatic properties and platelet dysfunction may further enhance positive predictive value, which was found to be weak in some studies although simultaneously have had a high negative predictive value. With aim to evaluate if intra-operative assessment of hemostatic properties using point-of-care devices provides bleeding prediction, we conducted prospective trial in which we showed that both MEA and TEM were accurate in predicting excessive bleeding [2]. Put briefly our study showed that pre – and intra-operative MEA and TEM findings were useful for prediction of excessive bleeding after cardiosurgical procedures [2]. The best predictors were the tests performed after completion of surgical procedure [2]. The reason for higher accuracy of intra-operatively performed testing is probably in the fact that intra-operative