http://informahealthcare.com/plt ISSN: 0953-7104 (print), 1369-1635 (electronic) Platelets, 2015; 26(1): 38–42 ! 2015 Informa UK Ltd. DOI: 10.3109/09537104.2013.869312
ORIGINAL ARTICLE
Rebalanced hemostasis in patients with idiopathic thrombocytopenic purpura Won Ho Kim1,2, Jung Bo Park1, Chul Won Jung3, & Gaab Soo Kim1 1
Department of Anesthesiology and Pain Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea, 2Department of Anesthesiology and Pain Medicine, Samsung Changwon Hospital, Sungkyunkwan University, School of Medicine, Changwon, Republic of Korea, and 3Division of Hematology and Oncology, Department of Medicine, Samsung Medical Center, Sungkyunkwan University, School of Medicine, Seoul, Republic of Korea Abstract
Keywords
Previous laboratory and clinical data have shown evidence for the concept of rebalanced hemostasis in liver disease. We evaluate whether this concept of rebalanced hemostasis can be applied in patients with idiopathic thrombocytopenic purpura (ITP). Twenty patients with ITP (platelet count5100 109 /l) who visited our hospital were enrolled. We measured the von Willebrand factor (vWF) antigen levels and performed native blood thromboelastography (TEG) to evaluate the hemostasis. As a subgroup analysis, we compared patients with elevated vWF levels with those with normal levels. Bleeding symptoms of the patients were followed up for 6 months. The mean (SD [IQR]) platelet count was 44.23 109 /l (25.78 [27.00–60.50]). The following TEG parameters were within the normal range in most patients (number of patients with a normal value): clotting time (17), clot formation time (17), a-angle (15), maximum clot formation (10), and maximum lysis (12). The mean (SD) vWF antigen level (%) was 163% (80). There were eight patients (40%) with elevated vWF antigen levels [218% (104) vs. 126% (19), p ¼ 0.007, elevated vs. normal patients, respectively]. Those with elevated vWF antigen levels were older [58 year (10) vs. 40 year (13), p ¼ 0.004] and had a longer disease status [67 months (39) vs. 33 months (25), p ¼ 0.028]. Although the platelet count was not different, the CFT was shorter [287 (104) vs. 561 (291), p ¼ 0.042] and the a-angle was larger [49 (6) vs. 34 (15), p ¼ 0.033] in those with elevated vWF antigen levels. There were no patients with major bleeding events during the follow-up period. Four patients showed minor bleeding events (n ¼ 1 vs. n ¼ 3, elevated vs. normal patients, respectively). We found that the vWF antigen level was elevated and the TEG profiles were better in older ITP patients with longer disease statuses. Patients with ITP appeared to achieve a rebalance hemostasis through an elevation of their plasma vWF antigen levels and hemostatic changes that promote thrombosis. Measuring the vWF antigen levels and performing TEG analysis can help determine the treatment strategy in ITP patients.
Bleeding, idiopathic thrombocytopenic purpura, platelet count, thromboelastography, von Willebrand factor
Introduction Idiopathic thrombocytopenic purpura (ITP) refers to a bleeding condition characterized by thrombocytopenia that results from the destruction of platelets through the targeting of their membrane glycoproteins. The clinical features of adult patients include petechiae, purpura and easy bruising [1]. Wang et al. reported that the platelet count does not correlate with function and may not predict the bleeding risk, especially in severely thrombocytopenic patients [2–4]. Mellet et al. suggested that thromboelastography (TEG) can evaluate platelet function and predict bleeding diatheses [5,6]. A recent investigation studied the role of TEG in patients with ITP and showed that the maximum clot formation
Correspondence: Gaab Soo Kim, MD, PhD, Professor, Department of Anesthesiology and Pain Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Irwon-Dong, Gangnam-Gu, Seoul 135-710, Republic of Korea. Tel: +82 2 3410 1928. Fax: +82 2 3410 0360. E-mail: [email protected]
History Received 12 July 2013 Revised 18 November 2013 Accepted 20 November 2013 Published online 16 January 2014
(MCF) can predict bleeding in ITP patients, suggesting that TEG is superior to other hemostatic tests [7]. There have also been several reports proposing that the treatment and perioperative transfusion in ITP patients can be guided by TEG [8–10]. Previous laboratory models and clinical data have shown evidence for a rebalanced hemostasis in liver disease with thrombocytopenia [11–15]. Rebalanced hemostasis is a concept that changes in prohemostatic pathways are counteracted by changes in antihemostatic pathways. There is a deficiency of procoagulant and antifibrinolytic factors along with a deficiency of naturally occuring anticoagulant and profibrinolytics in patients with severe liver disease [14]. As there is a decrease in both pro- and antihemostatic systems in patients with liver disease, the transfusion of blood products is suggested to be restricted [16]. This concept can explain a lack of major blood loss in many patients with end-stage liver disease undergoing major operations [17,18]. For example, elevated levels of von Willebrand factor (vWF) antigen [19] and the enhancement of vWF protein expresison has been reported in patients with liver disease [20]. The elevated vWF antigen level was shown to
Hemostasis in patients with ITP
DOI: 10.3109/09537104.2013.869312
compensate for thrombocytopenia and platelet dysfunction in laboratory models [21]. We hypothesized that the concept of rebalanced hemostasis can be applied in patients with ITP. We expected that the vWF antigen levels would be elevated and that the TEG parameters related to the platelet counts would be better than expected in ITP patients. Therefore, we studied whether any evidence of rebalanced hemostasis could be demonstrated in patients with ITP by measuring the vWF antigen levels and performing native blood TEG along with conventional coagulation tests.
Methods This prospective observational study was permitted by the institutional review board of our institution (2012-01-085) and the study protocol was registered at http://www.clinicaltrials.gov (NCT01571349). After obtaining written informed consent, patients who visited the hematology out-patient clinic with an established diagnosis of ITP and a last platelet count less than 100 109 /l were enrolled in this study. When the patients visited the outpatient clinic two weeks after enrollement for their followup, we performed tests for platelet count, prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen, vWF antigen level and native blood TEG to evaluate hemostasis. For a subgroup analysis, we compared patients with elevated vWF antigen levels and those with normal levels. Major and minor bleeding symptoms were followed-up and recorded according to outpatient clinical review during 6 months after enrollment. We defined major bleeding when it required hospital admission or was associated with fall in hemoglobin of at least 2 g/dl or both. Petechia, purpura, eccymosis, gum bleeding, and mild epistaxis were classified as minor bleeding. Blood samples for the platelet count were withdrawn into Becton Dickinson EDTA tubes. Platelet counts were recorded using a Beckman Coulter Gen-S SM, USA automated blood counting device. Another blood sample was obtained in a 4.5 ml vacutainer (Becton Dickinson, Franklin Lakes, NJ) containing 3.2% trisodium citrate with a citrate/blood ratio of 1:9 for subsequent coagulation analysis. The laboratory tests of coagulation, including PT and aPTT, were performed on a fully automated STA impact device (Diagnostica Stago, Asnie`res, France). PT was performed using a Neoplastic CI Plus and aPTT was performed using rabbit brain cephalin with kaolin as an activator. Fibrinogen levels were measured with a STA-fibrinogen kit by the Clauss clotting method (Becton Dickinson, Franklin Lakes, NJ). The normal ranges for these tests in our laboratory were as follows: aPTT (29–42 s), PT (12.6–14.9 s) and fibrinogen (182–380 mg/dl). The vWF antigen levels in plasma were measured using an enzyme-linked immunosorbent assay (ELISA Asserachrom vWF, Diagnostica Stago). Native blood TEG analysis was performed with the ROTEM Coagulation Analyzer (Pentapharm, Munich, Germany). All TEG samples were analyzed within 60 min of blood collection. 300 ml of citrated whole blood was used and recalcified with 20 ml of 0.2 mol l1 CaCl2 (star-TEM; Pentapharm, Munich, Germany). The normal reference range in our laboratory was as follows: (MCF ¼ maximum amplitude, MA 40–65 mm), clotting time (CT, 300–1000 s), clot formation time (CFT 150–700 s). The tests were automatically performed after the injection of the blood sample with an automated pipette and the calculated graphical results were obtained by the device computer. SPSS software (SPSS 20.0, Chicago IL) was used for statistical analyses. Data are presented as mean (SD), median (inter-quartile range), or number (%). The Shapiro–Wilk test with visual inspection of the histograms and Q-Q plots was used to test the normality of the distribution of data. Comparison of the
39
continuous variables of patients with normal vWF and those with elevated vWF was performed using the independent t test or Mann–Whitney U test according to the normality of variables. The Chi-square test or the Fisher’s exact test according to the expected counts was applied to compare the categorical variables. Correlations between variables were determined by calculating the Pearson and Spearman correlation coefficients. In all cases, a p value of 50.05 was considered significant.
Results Twenty patients with ITP (platelet count5100 109 /l) during the period between April 2012 and December 2012 were enrolled in this study. Patients characteristics are shown in Table I. Five patients were under observation and 15 patients had platelet counts less than 100 109 /l despite therapy (methyl prednisolone, danazol, azathioprine and cyclosporine A). Three patients had a history of splenectomy. The mean (SD [IQR]) platelet count was 44.23 109 /l (25.78 [27.00–60.50]). The TEG parameters were within the normal range in most patients. The following parameters related to coagulation were within the normal range: CT in 17 patients, CFT in 17 patients, a-angle in 15 patients and MCF in 10 patients. Log10 [Platelet (/ml)] was positively correlated with MCF (r ¼ 0.914, p50.001), negatively correlated with CFT (r ¼ 0.564, p ¼ 0.019), and positively correlated with the a-angle (r ¼ 0.772, p50.001; Figure 1). The mean (SD) vWF antigen level (%) was 163% (80). [normal range 55–155% in type O blood, 71–186% in non-type O blood]. There were eight patients (40%) with elevated vWF antigen levels [218% (104) vs. 126% (19), p ¼ 0.007, elevated vs. normal patients, respectively]. Comparison of the patient characteristics and coagulation profiles between patients with elevated vWF and those with normal vWF are shown in Table II. Those with elevated vWF antigen levels were older patients (58 years old (10) vs. 40 years old (13), p ¼ 0.004) and, had a longer disease status [67 months (39) vs. 33 months (25), p ¼ 0.028]. Although the platelet count was not different, the CFT was shorter [287 (104) vs. 561 (291), p ¼ 0.042] and the a-angle was larger [49 (6) vs. 34 (15), p ¼ 0.033] in those with elevated vWF antigen levels. There were no patients with major bleeding events during the
Table I. Patient characteristics. Characteristic Age, year Gender, male/female Body weight, kg Height, cm Body-mass index ABO blood type, A/B/O/AB, n Hypertension, n Diabetes mellitus, n Angina pectoris, n Chronic kidney disease, n Platelet count, 109 /l Treatment, n Observation Methylprednisolone Danazol Azathioprine Cyclosporine A Splenectomy, n vWF antigen level. % Elevated vWF level, n
Patients (n ¼ 20) 49 (15) 5/15 66 (8) 162 (9) 25 (3) 7/6/6/2 2 (10%) 1 (5%) 1 (5%) 1 (5%) 44.23 (25.78) 5 10 5 1 2 3 163 8
(25%) (50%) (20%) (10%) (10%) (15%) (80) (40%)
vWF, von Willbrand factor. Values are expressed as mean (SD), number (proportion).
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W. H. Kim et al.
Figure 1. Correlation between platelet count and maximum clot formation (r ¼ 0.914, p50.001), a-angle (r ¼ 0.772, p50.001), and clot formation time (r ¼ 0.564, p ¼ 0.019).
follow-up period of 6 months. Four patients showed minor bleeding events (petechia, purpura, ecchymosis, epistaxis, n ¼ 1 vs. n ¼ 3, elevated vs. normal patients, respectively).
Discussion We examined the vWF antigen levels and TEG parameters in ITP patients with platelet counts less than 100 109 /L. The vWF antigen levels were in the upper range of normal or elevated in most patients. We compared patients with normal vWF antigen levels and those with elevated vWF antigen levels to investigate whether there was a difference in their clinical characteristics or coagulation profiles. We found that the TEG profiles were better in patients with elevated vWF. They were older and had a longer disease status. With these results, we conclude that patients with ITP appear to achieve a rebalanced hemostasis through an elevation of their plasma vWF antigen levels and the undergoing of hemostatic changes promoting thrombosis. The risk of bleeding in ITP patients increases as platelet count decreases. However, the platelet count does not necessarily reflect its function and was not an independent predictor of bleeding risk as compared to platelet function analyses in previous studies [2,4]. Some of the heterogeneity in bleeding in ITP patients may be due to the fact that certain autoantibodies may impair qualitative
Platelets, 2015; 26(1): 38–42
function of platelets as well as promote the clearance to reduce the count [1]. Therefore, a modality to evaluate the platelet function in ITP patients is required. A previous study reported that TEG can adequately evaluate coagulation in ITP patients and MCF appears to be the most important TEG parameter in predicting bleeding in ITP patients [7]. Although we could not evaluate the predictability of MCF for bleeding due to our small sample size, MCF was most strongly correlated with platelet count in our study. MCF measures clot strength and has been suggested to represent the effect of platelet counts on TEG [22,23]. MCF assesses platelet count and function, as well as fibrinogen activity [24]. CFT and the a-angle reflect the rate of clot formation and are influenced by reduced platelet numbers. There have been many studies supporting the concept of rebalanced hemostasis in patients with liver disease, but no study had been performed with ITP patients. The present study is the first study to provide evidence of this concept in ITP patients. Tripodi et al. [11] demonstrated an example of rebalanced hemostasis with a laboratory technique to show the total thrombin genaration capacity in patients with liver disease. The authors took the reduction of anti-coagulant factors in patients with liver disease into account by measuring thrombin generation in the presence of thrombomodulin. The thrombin generation was within the normal range despite a prolonged PT. They pointed out the limitation of conventional coagulation tests in patients with chronic liver disease. Warnaar et al. [14] reviewed the rebalancing of the hemostatic system in patients with end-stage liver disease. They addressed the observation that thromboembolic complications do paradoxically occur in patients with cirrhosis [25], which can be explained by a rebalanced hemostatic system. We found that 8 of the 20 patients with ITP had elevated vWF antigen levels and better coagulation profile analyzed by TEG. In line with this, a previous study has evaluated vWF protease activity in patients with thrombocytopenic disorders including ITP [26]. Reduced protease activity was observed in 6 of the 20 patients with ITP and 9 of the 20 patients with thrombotic thrombocytopenic purpura. The most marked decreases in vWF protease activity were noted in patients with severe thrombocytopenia or higher vWF antigen levels. The clinical implication of this study is that the treatment strategy for ITP patients should consider this rebalanced hemostasis on a case-by-case basis. TEG analysis and the measurement of vWF antigen levels could help evaluate the true coagulation status in ITP patients. The coagulation status measured by TEG was different between those with elevated vWF antigen levels and those without, although the platelet counts were similar. Patients with longer disease status seemed to rebalance their hemostasis through an elevation of their vWF antigen levels. The CFT was significantly shorter and the a-angle was significantly greater in those with elevated vWF antigen levels. Therefore, the treatment policy of ITP should not solely depend on the platelet counts. The clinician should take the longevity of disease status into account and consider modern laboratory techniques that can evaluate the platelet function and overall coagulation status. Perioperative transfusion policies should consider rebalanced hemostasis rather than solely the platelet counts. There was a case report that described a patients with ITP who successfully underwent coronary artery bypass graft with cardiopulmonary bypass without the transfusion of allogeneic platelet [8]. In this study, pre- and postoperative TEG showed essentially normal coagulation profiles despite low platelet counts and the authors suggested that the correlation between platelet counts and hemostasis was not predictable. The results of TEG and the vWF antigen levels along with platelet count can be used to evaluate perioperative hemostasis status in ITP patients. If a patient whose preoperative vWF antigen levels were elevated and TEG profiles were
Hemostasis in patients with ITP
DOI: 10.3109/09537104.2013.869312
41
Table II. Patient characteristics and coagulation profiles in patients whose vWF antigen levels are elevated or normal. Characteristic n, % Age, year Gender, M/F Body-mass index Disease status, months Platelet count, 109 /l Observation, n Treatment Methylpredisolone, n Danazol, n Azathioprine, n Cyclosporine, n Splenectomy, n Major bleeding event during follow up, n Minor bleeding event during follow up, n vWF antigen level, % PT, second aPTT, second Fibrinogen, mg/dl Thromboelastography Coagulation time Clot formation time Maximum clot formation a-angle
Patients with elevated vWF
Patients with normal vWF
p Value
8 (40%) 58 (10) 3/5 23.5 (3.0) 67 (39) 52.50 (24.02) 1 (13%)
12 (60%) 40 (13) 2/10 26.4 (3.0) 33 (25) 34.25 (20.49) 4 (33%)
0.004* 0.347 0.219 0.028* 0.101 0.603
4 (50%) 2 (25%) 1 (13%) 2 (25%) 1 (13%) 0 1 (5%) 218 (104) 12.7 (0.6) 32.3 (3.6) 310 (112)
6 (50%) 3 (25%) 0 0 2 (17%) 0 3 (15%) 126 (19) 12.6 (0.6) 32.9 (1.3) 263 (52)
0.999 0.999 – – 0.999
623 287 42 49
812 561 33 34
0.133 0.042* 0.064 0.033*
(134) (104) (6) (6)
(271) (292) (9) (15)
0.007* 0.730 0.625 0.242
vWF, von Willebrand factor; PT, prothrombin time; aPTT, activated partial thromboplastin time. Values are expressed as mean (SD), number (proportion). p Values are the results of unpaired t tests or Mann–Whitney U tests according to the normality of the variable, or the Fisher’s exact test. *significant difference between groups.
relatively normal underwent splenectomy [27,28], no platelet transfusion would be required. Furthermore, a temporary hypercoagulable status may occur when the platelet count rapidly rises postoperatively. In this case, the use of an anticoagulant rather than platelet transfusion may be required. The present study has several limitations. First, this study was observational and had a small sample size. The incidence of bleeding events was too low to evaluate the predictability of vWF antigen levels or TEG parameters for bleeding risk. Second, we did not measure all of the components of the coagulation cascade including the coagulation factors. We also could not provide information about secondary hemostasis along with fibrinolysis. Third, it was reported that there is a linear correlation between age and plasma level of vWF antigen levels [29]. However, because local age-adjusted reference ranges for vWF antigen are not available currently, it is not possible to answer the question whether the increased vWF antigen levels in the patients with elevated vWF antigen level is more than that would be expected with ageing alone in the normal population. Fourth, a formal age and gender matched control group was not recruited to this study. The comparison between ITP patients and normal control was not possible. Fifth, as the sample size was small and disease severity was not controlled in this study, this study cannot answer the question whether the elevated vWF antigen level group had more severe underlying disease and had required more treatment. In conclusion, we found that older ITP patients with longer disease status had more elevated vWF antigen levels and better TEG profiles. Patients with ITP appear to achieve a rebalanced hemostasis by an elevation of their plasma vWF antigen levels and the undergoing of hemostatic changes promoting thrombosis. Measuring the vWF antigen levels and performing TEG analysis could help determine the treatment strategy in ITP patients.
Declaration of interest The authors report no conflict of interests.
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13. Lisman T, Caldwell SH, Leebeek FW, Porte RJ. Is chronic liver disease associated with a bleeding diathesis? J Thromb Haemost 2006;4:2059–2060. 14. Warnaar N, Lisman T, Porte RJ. The two tales of coagulation in liver transplantation. Curr Opin Organ Transplant 2008;13:298–303. 15. Mannucci PM. Abnormal hemostasis tests and bleeding in chronic liver disease: Are they related? No. J Thromb Haemost 2006;4: 721–723. 16. van der Werf J, Porte RJ, Lisman T. Hemostasis in patients with liver disease. Acta Gastroenterol Belg 2009;72:433–440. 17. Massicotte L, Lenis S, Thibeault L, Sassine MP, Seal RF, Roy A. Effect of low central venous pressure and phlebotomy on blood product transfusion requirements during liver transplantations. Liver Transpl 2006;12:117–123. 18. de Boer MT, Molenaar IQ, Hendriks HG, Slooff MJ, Porte RJ. Minimizing blood loss in liver transplantation: Progress through research and evolution of techniques. Dig Surg 2005;22:265–275. 19. Ferro D, Quintarelli C, Lattuada A, Leo R, Alessandroni M, Mannucci PM, Violi F. High plasma levels of von Willebrand factor as a marker of endothelial perturbation in cirrhosis: Relationship to endotoxemia. Hepatology 1996;23:1377–1383. 20. Hollestelle MJ, Geertzen HG, Straatsburg IH, van Gulik TM, van Mourik JA. Factor VIII expression in liver disease. Thromb Haemost 2004;91:267–275. 21. Lisman T, Bongers TN, Adelmeijer J, Janssen HL, de Maat MP, de Groot PG, Leebeek FW. Elevated levels of von Willebrand Factor in cirrhosis support platelet adhesion despite reduced functional capacity. Hepatology 2006;44:53–61.
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22. Kang YG, Martin DJ, Marquez J, Lewis JH, Bontempo FA, Shaw BW Jr., Starzl TE, Winter PM. Intraoperative changes in blood coagulation and thrombelastographic monitoring in liver transplantation. Anesth Analg 1985;64:888–896. 23. Salooja N, Perry DJ. Thrombelastography. Blood Coagul Fibrinolysis 2001;12:327–337. 24. Chen A, Teruya J. Global hemostasis testing thromboelastography: Old technology, new applications. Clin Lab Med 2009;29:391–407. 25. Navalgund AA, Kang Y, Sarner JB, Jahr JS, Gieraerts R. Massive pulmonary thromboembolism during liver transplantation. Anesth Analg 1988;67:400–402. 26. Moore JC, Hayward CP, Warkentin TE, Kelton JG. Decreased von Willebrand factor protease activity associated with thrombocytopenic disorders. Blood 2001;98:1842–1846. 27. Kojouri K, Vesely SK, Terrell DR, George JN. Splenectomy for adult patients with idiopathic thrombocytopenic purpura: A systematic review to assess long-term platelet count responses, prediction of response, and surgical complications. Blood 2004;104: 2623–2634. 28. Gibson M, Sehon JK, White S, Zibari GB, Johnson LW. Splenectomy for idiopathic thrombocytopenic purpura: A five-year retrospective review. Am Surg 2000;66:952–954; discussion 955. 29. Favaloro EJ, Soltani S, McDonald J, Grezchnik E, Easton L, Favaloro JW. Reassessment of ABO blood group, sex, and age on laboratory parameters used to diagnose von Willebrand disorder: Potential influence on the diagnosis vs the potential association with risk of thrombosis. Am J Clin Pathol 2005;124:910–917.
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ORIGINAL ARTICLE
Rebalanced hemostasis in patients with idiopathic thrombocytopenic purpura Won Ho Kim1,2, Jung Bo Park1, Chul Won Jung3, & Gaab Soo Kim1 1
Department of Anesthesiology and Pain Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea, 2Department of Anesthesiology and Pain Medicine, Samsung Changwon Hospital, Sungkyunkwan University, School of Medicine, Changwon, Republic of Korea, and 3Division of Hematology and Oncology, Department of Medicine, Samsung Medical Center, Sungkyunkwan University, School of Medicine, Seoul, Republic of Korea Abstract
Keywords
Previous laboratory and clinical data have shown evidence for the concept of rebalanced hemostasis in liver disease. We evaluate whether this concept of rebalanced hemostasis can be applied in patients with idiopathic thrombocytopenic purpura (ITP). Twenty patients with ITP (platelet count5100 109 /l) who visited our hospital were enrolled. We measured the von Willebrand factor (vWF) antigen levels and performed native blood thromboelastography (TEG) to evaluate the hemostasis. As a subgroup analysis, we compared patients with elevated vWF levels with those with normal levels. Bleeding symptoms of the patients were followed up for 6 months. The mean (SD [IQR]) platelet count was 44.23 109 /l (25.78 [27.00–60.50]). The following TEG parameters were within the normal range in most patients (number of patients with a normal value): clotting time (17), clot formation time (17), a-angle (15), maximum clot formation (10), and maximum lysis (12). The mean (SD) vWF antigen level (%) was 163% (80). There were eight patients (40%) with elevated vWF antigen levels [218% (104) vs. 126% (19), p ¼ 0.007, elevated vs. normal patients, respectively]. Those with elevated vWF antigen levels were older [58 year (10) vs. 40 year (13), p ¼ 0.004] and had a longer disease status [67 months (39) vs. 33 months (25), p ¼ 0.028]. Although the platelet count was not different, the CFT was shorter [287 (104) vs. 561 (291), p ¼ 0.042] and the a-angle was larger [49 (6) vs. 34 (15), p ¼ 0.033] in those with elevated vWF antigen levels. There were no patients with major bleeding events during the follow-up period. Four patients showed minor bleeding events (n ¼ 1 vs. n ¼ 3, elevated vs. normal patients, respectively). We found that the vWF antigen level was elevated and the TEG profiles were better in older ITP patients with longer disease statuses. Patients with ITP appeared to achieve a rebalance hemostasis through an elevation of their plasma vWF antigen levels and hemostatic changes that promote thrombosis. Measuring the vWF antigen levels and performing TEG analysis can help determine the treatment strategy in ITP patients.
Bleeding, idiopathic thrombocytopenic purpura, platelet count, thromboelastography, von Willebrand factor
Introduction Idiopathic thrombocytopenic purpura (ITP) refers to a bleeding condition characterized by thrombocytopenia that results from the destruction of platelets through the targeting of their membrane glycoproteins. The clinical features of adult patients include petechiae, purpura and easy bruising [1]. Wang et al. reported that the platelet count does not correlate with function and may not predict the bleeding risk, especially in severely thrombocytopenic patients [2–4]. Mellet et al. suggested that thromboelastography (TEG) can evaluate platelet function and predict bleeding diatheses [5,6]. A recent investigation studied the role of TEG in patients with ITP and showed that the maximum clot formation
Correspondence: Gaab Soo Kim, MD, PhD, Professor, Department of Anesthesiology and Pain Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Irwon-Dong, Gangnam-Gu, Seoul 135-710, Republic of Korea. Tel: +82 2 3410 1928. Fax: +82 2 3410 0360. E-mail: [email protected]
History Received 12 July 2013 Revised 18 November 2013 Accepted 20 November 2013 Published online 16 January 2014
(MCF) can predict bleeding in ITP patients, suggesting that TEG is superior to other hemostatic tests [7]. There have also been several reports proposing that the treatment and perioperative transfusion in ITP patients can be guided by TEG [8–10]. Previous laboratory models and clinical data have shown evidence for a rebalanced hemostasis in liver disease with thrombocytopenia [11–15]. Rebalanced hemostasis is a concept that changes in prohemostatic pathways are counteracted by changes in antihemostatic pathways. There is a deficiency of procoagulant and antifibrinolytic factors along with a deficiency of naturally occuring anticoagulant and profibrinolytics in patients with severe liver disease [14]. As there is a decrease in both pro- and antihemostatic systems in patients with liver disease, the transfusion of blood products is suggested to be restricted [16]. This concept can explain a lack of major blood loss in many patients with end-stage liver disease undergoing major operations [17,18]. For example, elevated levels of von Willebrand factor (vWF) antigen [19] and the enhancement of vWF protein expresison has been reported in patients with liver disease [20]. The elevated vWF antigen level was shown to
Hemostasis in patients with ITP
DOI: 10.3109/09537104.2013.869312
compensate for thrombocytopenia and platelet dysfunction in laboratory models [21]. We hypothesized that the concept of rebalanced hemostasis can be applied in patients with ITP. We expected that the vWF antigen levels would be elevated and that the TEG parameters related to the platelet counts would be better than expected in ITP patients. Therefore, we studied whether any evidence of rebalanced hemostasis could be demonstrated in patients with ITP by measuring the vWF antigen levels and performing native blood TEG along with conventional coagulation tests.
Methods This prospective observational study was permitted by the institutional review board of our institution (2012-01-085) and the study protocol was registered at http://www.clinicaltrials.gov (NCT01571349). After obtaining written informed consent, patients who visited the hematology out-patient clinic with an established diagnosis of ITP and a last platelet count less than 100 109 /l were enrolled in this study. When the patients visited the outpatient clinic two weeks after enrollement for their followup, we performed tests for platelet count, prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen, vWF antigen level and native blood TEG to evaluate hemostasis. For a subgroup analysis, we compared patients with elevated vWF antigen levels and those with normal levels. Major and minor bleeding symptoms were followed-up and recorded according to outpatient clinical review during 6 months after enrollment. We defined major bleeding when it required hospital admission or was associated with fall in hemoglobin of at least 2 g/dl or both. Petechia, purpura, eccymosis, gum bleeding, and mild epistaxis were classified as minor bleeding. Blood samples for the platelet count were withdrawn into Becton Dickinson EDTA tubes. Platelet counts were recorded using a Beckman Coulter Gen-S SM, USA automated blood counting device. Another blood sample was obtained in a 4.5 ml vacutainer (Becton Dickinson, Franklin Lakes, NJ) containing 3.2% trisodium citrate with a citrate/blood ratio of 1:9 for subsequent coagulation analysis. The laboratory tests of coagulation, including PT and aPTT, were performed on a fully automated STA impact device (Diagnostica Stago, Asnie`res, France). PT was performed using a Neoplastic CI Plus and aPTT was performed using rabbit brain cephalin with kaolin as an activator. Fibrinogen levels were measured with a STA-fibrinogen kit by the Clauss clotting method (Becton Dickinson, Franklin Lakes, NJ). The normal ranges for these tests in our laboratory were as follows: aPTT (29–42 s), PT (12.6–14.9 s) and fibrinogen (182–380 mg/dl). The vWF antigen levels in plasma were measured using an enzyme-linked immunosorbent assay (ELISA Asserachrom vWF, Diagnostica Stago). Native blood TEG analysis was performed with the ROTEM Coagulation Analyzer (Pentapharm, Munich, Germany). All TEG samples were analyzed within 60 min of blood collection. 300 ml of citrated whole blood was used and recalcified with 20 ml of 0.2 mol l1 CaCl2 (star-TEM; Pentapharm, Munich, Germany). The normal reference range in our laboratory was as follows: (MCF ¼ maximum amplitude, MA 40–65 mm), clotting time (CT, 300–1000 s), clot formation time (CFT 150–700 s). The tests were automatically performed after the injection of the blood sample with an automated pipette and the calculated graphical results were obtained by the device computer. SPSS software (SPSS 20.0, Chicago IL) was used for statistical analyses. Data are presented as mean (SD), median (inter-quartile range), or number (%). The Shapiro–Wilk test with visual inspection of the histograms and Q-Q plots was used to test the normality of the distribution of data. Comparison of the
39
continuous variables of patients with normal vWF and those with elevated vWF was performed using the independent t test or Mann–Whitney U test according to the normality of variables. The Chi-square test or the Fisher’s exact test according to the expected counts was applied to compare the categorical variables. Correlations between variables were determined by calculating the Pearson and Spearman correlation coefficients. In all cases, a p value of 50.05 was considered significant.
Results Twenty patients with ITP (platelet count5100 109 /l) during the period between April 2012 and December 2012 were enrolled in this study. Patients characteristics are shown in Table I. Five patients were under observation and 15 patients had platelet counts less than 100 109 /l despite therapy (methyl prednisolone, danazol, azathioprine and cyclosporine A). Three patients had a history of splenectomy. The mean (SD [IQR]) platelet count was 44.23 109 /l (25.78 [27.00–60.50]). The TEG parameters were within the normal range in most patients. The following parameters related to coagulation were within the normal range: CT in 17 patients, CFT in 17 patients, a-angle in 15 patients and MCF in 10 patients. Log10 [Platelet (/ml)] was positively correlated with MCF (r ¼ 0.914, p50.001), negatively correlated with CFT (r ¼ 0.564, p ¼ 0.019), and positively correlated with the a-angle (r ¼ 0.772, p50.001; Figure 1). The mean (SD) vWF antigen level (%) was 163% (80). [normal range 55–155% in type O blood, 71–186% in non-type O blood]. There were eight patients (40%) with elevated vWF antigen levels [218% (104) vs. 126% (19), p ¼ 0.007, elevated vs. normal patients, respectively]. Comparison of the patient characteristics and coagulation profiles between patients with elevated vWF and those with normal vWF are shown in Table II. Those with elevated vWF antigen levels were older patients (58 years old (10) vs. 40 years old (13), p ¼ 0.004) and, had a longer disease status [67 months (39) vs. 33 months (25), p ¼ 0.028]. Although the platelet count was not different, the CFT was shorter [287 (104) vs. 561 (291), p ¼ 0.042] and the a-angle was larger [49 (6) vs. 34 (15), p ¼ 0.033] in those with elevated vWF antigen levels. There were no patients with major bleeding events during the
Table I. Patient characteristics. Characteristic Age, year Gender, male/female Body weight, kg Height, cm Body-mass index ABO blood type, A/B/O/AB, n Hypertension, n Diabetes mellitus, n Angina pectoris, n Chronic kidney disease, n Platelet count, 109 /l Treatment, n Observation Methylprednisolone Danazol Azathioprine Cyclosporine A Splenectomy, n vWF antigen level. % Elevated vWF level, n
Patients (n ¼ 20) 49 (15) 5/15 66 (8) 162 (9) 25 (3) 7/6/6/2 2 (10%) 1 (5%) 1 (5%) 1 (5%) 44.23 (25.78) 5 10 5 1 2 3 163 8
(25%) (50%) (20%) (10%) (10%) (15%) (80) (40%)
vWF, von Willbrand factor. Values are expressed as mean (SD), number (proportion).
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Figure 1. Correlation between platelet count and maximum clot formation (r ¼ 0.914, p50.001), a-angle (r ¼ 0.772, p50.001), and clot formation time (r ¼ 0.564, p ¼ 0.019).
follow-up period of 6 months. Four patients showed minor bleeding events (petechia, purpura, ecchymosis, epistaxis, n ¼ 1 vs. n ¼ 3, elevated vs. normal patients, respectively).
Discussion We examined the vWF antigen levels and TEG parameters in ITP patients with platelet counts less than 100 109 /L. The vWF antigen levels were in the upper range of normal or elevated in most patients. We compared patients with normal vWF antigen levels and those with elevated vWF antigen levels to investigate whether there was a difference in their clinical characteristics or coagulation profiles. We found that the TEG profiles were better in patients with elevated vWF. They were older and had a longer disease status. With these results, we conclude that patients with ITP appear to achieve a rebalanced hemostasis through an elevation of their plasma vWF antigen levels and the undergoing of hemostatic changes promoting thrombosis. The risk of bleeding in ITP patients increases as platelet count decreases. However, the platelet count does not necessarily reflect its function and was not an independent predictor of bleeding risk as compared to platelet function analyses in previous studies [2,4]. Some of the heterogeneity in bleeding in ITP patients may be due to the fact that certain autoantibodies may impair qualitative
Platelets, 2015; 26(1): 38–42
function of platelets as well as promote the clearance to reduce the count [1]. Therefore, a modality to evaluate the platelet function in ITP patients is required. A previous study reported that TEG can adequately evaluate coagulation in ITP patients and MCF appears to be the most important TEG parameter in predicting bleeding in ITP patients [7]. Although we could not evaluate the predictability of MCF for bleeding due to our small sample size, MCF was most strongly correlated with platelet count in our study. MCF measures clot strength and has been suggested to represent the effect of platelet counts on TEG [22,23]. MCF assesses platelet count and function, as well as fibrinogen activity [24]. CFT and the a-angle reflect the rate of clot formation and are influenced by reduced platelet numbers. There have been many studies supporting the concept of rebalanced hemostasis in patients with liver disease, but no study had been performed with ITP patients. The present study is the first study to provide evidence of this concept in ITP patients. Tripodi et al. [11] demonstrated an example of rebalanced hemostasis with a laboratory technique to show the total thrombin genaration capacity in patients with liver disease. The authors took the reduction of anti-coagulant factors in patients with liver disease into account by measuring thrombin generation in the presence of thrombomodulin. The thrombin generation was within the normal range despite a prolonged PT. They pointed out the limitation of conventional coagulation tests in patients with chronic liver disease. Warnaar et al. [14] reviewed the rebalancing of the hemostatic system in patients with end-stage liver disease. They addressed the observation that thromboembolic complications do paradoxically occur in patients with cirrhosis [25], which can be explained by a rebalanced hemostatic system. We found that 8 of the 20 patients with ITP had elevated vWF antigen levels and better coagulation profile analyzed by TEG. In line with this, a previous study has evaluated vWF protease activity in patients with thrombocytopenic disorders including ITP [26]. Reduced protease activity was observed in 6 of the 20 patients with ITP and 9 of the 20 patients with thrombotic thrombocytopenic purpura. The most marked decreases in vWF protease activity were noted in patients with severe thrombocytopenia or higher vWF antigen levels. The clinical implication of this study is that the treatment strategy for ITP patients should consider this rebalanced hemostasis on a case-by-case basis. TEG analysis and the measurement of vWF antigen levels could help evaluate the true coagulation status in ITP patients. The coagulation status measured by TEG was different between those with elevated vWF antigen levels and those without, although the platelet counts were similar. Patients with longer disease status seemed to rebalance their hemostasis through an elevation of their vWF antigen levels. The CFT was significantly shorter and the a-angle was significantly greater in those with elevated vWF antigen levels. Therefore, the treatment policy of ITP should not solely depend on the platelet counts. The clinician should take the longevity of disease status into account and consider modern laboratory techniques that can evaluate the platelet function and overall coagulation status. Perioperative transfusion policies should consider rebalanced hemostasis rather than solely the platelet counts. There was a case report that described a patients with ITP who successfully underwent coronary artery bypass graft with cardiopulmonary bypass without the transfusion of allogeneic platelet [8]. In this study, pre- and postoperative TEG showed essentially normal coagulation profiles despite low platelet counts and the authors suggested that the correlation between platelet counts and hemostasis was not predictable. The results of TEG and the vWF antigen levels along with platelet count can be used to evaluate perioperative hemostasis status in ITP patients. If a patient whose preoperative vWF antigen levels were elevated and TEG profiles were
Hemostasis in patients with ITP
DOI: 10.3109/09537104.2013.869312
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Table II. Patient characteristics and coagulation profiles in patients whose vWF antigen levels are elevated or normal. Characteristic n, % Age, year Gender, M/F Body-mass index Disease status, months Platelet count, 109 /l Observation, n Treatment Methylpredisolone, n Danazol, n Azathioprine, n Cyclosporine, n Splenectomy, n Major bleeding event during follow up, n Minor bleeding event during follow up, n vWF antigen level, % PT, second aPTT, second Fibrinogen, mg/dl Thromboelastography Coagulation time Clot formation time Maximum clot formation a-angle
Patients with elevated vWF
Patients with normal vWF
p Value
8 (40%) 58 (10) 3/5 23.5 (3.0) 67 (39) 52.50 (24.02) 1 (13%)
12 (60%) 40 (13) 2/10 26.4 (3.0) 33 (25) 34.25 (20.49) 4 (33%)
0.004* 0.347 0.219 0.028* 0.101 0.603
4 (50%) 2 (25%) 1 (13%) 2 (25%) 1 (13%) 0 1 (5%) 218 (104) 12.7 (0.6) 32.3 (3.6) 310 (112)
6 (50%) 3 (25%) 0 0 2 (17%) 0 3 (15%) 126 (19) 12.6 (0.6) 32.9 (1.3) 263 (52)
0.999 0.999 – – 0.999
623 287 42 49
812 561 33 34
0.133 0.042* 0.064 0.033*
(134) (104) (6) (6)
(271) (292) (9) (15)
0.007* 0.730 0.625 0.242
vWF, von Willebrand factor; PT, prothrombin time; aPTT, activated partial thromboplastin time. Values are expressed as mean (SD), number (proportion). p Values are the results of unpaired t tests or Mann–Whitney U tests according to the normality of the variable, or the Fisher’s exact test. *significant difference between groups.
relatively normal underwent splenectomy [27,28], no platelet transfusion would be required. Furthermore, a temporary hypercoagulable status may occur when the platelet count rapidly rises postoperatively. In this case, the use of an anticoagulant rather than platelet transfusion may be required. The present study has several limitations. First, this study was observational and had a small sample size. The incidence of bleeding events was too low to evaluate the predictability of vWF antigen levels or TEG parameters for bleeding risk. Second, we did not measure all of the components of the coagulation cascade including the coagulation factors. We also could not provide information about secondary hemostasis along with fibrinolysis. Third, it was reported that there is a linear correlation between age and plasma level of vWF antigen levels [29]. However, because local age-adjusted reference ranges for vWF antigen are not available currently, it is not possible to answer the question whether the increased vWF antigen levels in the patients with elevated vWF antigen level is more than that would be expected with ageing alone in the normal population. Fourth, a formal age and gender matched control group was not recruited to this study. The comparison between ITP patients and normal control was not possible. Fifth, as the sample size was small and disease severity was not controlled in this study, this study cannot answer the question whether the elevated vWF antigen level group had more severe underlying disease and had required more treatment. In conclusion, we found that older ITP patients with longer disease status had more elevated vWF antigen levels and better TEG profiles. Patients with ITP appear to achieve a rebalanced hemostasis by an elevation of their plasma vWF antigen levels and the undergoing of hemostatic changes promoting thrombosis. Measuring the vWF antigen levels and performing TEG analysis could help determine the treatment strategy in ITP patients.
Declaration of interest The authors report no conflict of interests.
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