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Abstract

Background/Aim:

To evaluate the value of d-dimer, P-selectin, and platelet count in patients with cirrhotic portal hypertension (PHT) for prediction of portal vein thrombosis (PVT) after devascularization.

Methods:

A total of 137 patients with cirrhotic PHT who undergone devascularization from January 2012 to April 2014 were retrospectively reviewed, all of them were divided into 2 groups (PVT group and non-PVT group) by Doppler ultrasonography (DU) examination. The level of d-dimer, P-selectin, and platelet count was tested during the perioperative period.

Results:

In all, 38 (27.7%) patients were found to have PVT by DU examination postoperatively. In contrast to the non-PVT group, the level of d-dimer, P-selectin, and platelet count in the PVT group was much higher significantly at 1, 3, and 7 days after devascularization. (P < .05). However, in the 15 days after surgery, the difference in P-selectin between the 2 groups was not significant (P = .260). It was shown that the highest sensitivity of the 3 markers for PVT was d-dimer, the highest specificity belonged to P-selectin. The area under receiver–operating characteristic (ROC) curve of P-selectin was the biggest of the 3 markers. When the 3 markers were combined to be used to diagnose PVT, the sensitivity was increased to 0.907, with a slight drop of specificity to 0.693, the area under the ROC curve was 0.927.

Conclusion:

The level of d-dimer, P-selectin, and platelet count might be good candidate predictive markers for PVT in patients with cirrhotic PHT after devascularization. The combined test of the 3 markers can increase the value of prediction.

Keywords

devascularization portal vein thrombosis P-selectin platelet count

Introduction

Portal vein thrombosis (PVT) includes thrombosis in the portal vein, splenic vein, and superior mesenteric vein or intrahepatic portal vein branches as they form an interactive vascular system without valves. Portal vein thrombosis following devascularization occurs in 6.3% to 39.0% of patients and is mostly an unpredictable event.^1,2 Complete or partial occlusion of the portal venous system in patients with cirrhotic portal hypertension (PHT) may determine liver ischemia, with consequent deterioration of liver function, and a sudden increase in portal pressure. Some complications of liver cirrhosis such as variceal hemorrhage may develop and death eventually may occur.^3
–5 It is therefore important to identify markers that can predict the PVT and be used to guide prevention.

Platelet count had been used to evaluate the possibility of thrombosis and make prophylactic treatment, but some studies showed that patients with increased levels of platelet count were not accompanied with thrombosis.⁶ d-Dimer was a kind of fibrin degradation fragment and was the molecular marker in the fibrinolysis cycle.⁷ P-selectin was a cell adhesion molecule that is mainly produced by platelets and endothelial cells; it increased the activation of platelets and the adhesion of platelets to the endothelium.⁸ Recently, d-dimer and P-selectin have been shown to play an important role in diagnostic indicator for thrombotic diseases.^9,10 In this study, we investigated whether d-dimer, P-selectin, and platelet count have a better predictive value for PVT after devascularization in patients with cirrhotic PHT.

Methods

Patients and Study Design

Two hundred and sixty-seven consecutive patients who were diagnosed with hepatitis virus-related cirrhosis PHT between January 2012 and April 2014 at the 81st Hospital of P.L.A. in Nanjing, China, were included. The diagnoses of these patients were all confirmed by endoscopy, Doppler ultrasonography (DU), virological examination, biochemistry tests, and biopsy specimen of liver during the operation. All of them underwent the surgery procedure. The indications for operation were reported in our previous study.¹¹ All of the patients accompanied with no serious cardiopulmonary diseases and concomitant chronic duodenal ulcers. Patients whose serum levels of d-dimer, P-selectin, or platelet count during the time of diagnosis and treatment were not available were excluded. Any patients who may have been taking warfarin or aspirin would have also been excluded. Accordingly, 137 patients were enrolled into this study, which was approved by our hospital. The characteristics of the patients including age, gender, Child-Pugh’s score, and preoperative biochemical tests were summarized in Table 1. Biochemical tests were examined within 1 to 3 days preoperatively.

Table 1.

Preoperative Clinical Characteristics of Patients With Cirrhosis.

	PVT (n = 38)	Non-PVT (n = 99)	t/χ² Value	P Value
Age, mean ± SD, years	48.1 ± 7.1	45.2 ± 8.4	0.622	.231
Gender
Male	21	59	0.485	.316
Female	17	40	0.485	.316
Child-Pugh score	6.8 ± 1.3	7.0 ± 1.5	0.197	.628
PT, second	14.7 ± 2.9	14.1 ± 2.3	0.206	.595
TB, μmol/L	26.3 ± 4.0	26.8 ± 4.7	0.146	.742
ALT, IU/L	29.1 ± 7.8	27.6 ± 6.3	0.323	.382
AST, IU/L	27.7 ± 7.1	28.5 ± 6.4	0.272	.503
Operative time, min	248.1 ± 71.2	231.0 ± 63.6	0.375	.377
Intraoperative blood loss, mL	634.6 ± 68.5	592.7 ± 89.3	0.571	.259
FPP, cmH₂O	39.8 ± 7.6	36.3 ± 8.9	0.363	.498

Abbreviations: PVT, portal venous thrombosis; PT, prothrombin time; TB, total bilirubin; Alb, albumin; ALT, alanine aminotransferase; AST, aspartate aminotransferase; FPP, free portal pressure; SD, standard deviation; χ², chi-square.

The study protocol conformed to the guidelines by the institutional ethical committee. All patients gave their informed consent to be included in the study. The research was carried out according to the principles of The Declaration of Helsinki.

Portal Vein Thrombosis Diagnosis

The DU (ACUSON Sequoia 512, Color Doppler equipment, Germany) examination of the portal vein was performed pre-/postoperationally.¹² The study was performed in all cases by the same examiner to avoid interobserver variables. Spectral waveforms were obtained at measured angles of insonation of <60°. The preoperational examination was performed at 3 days before the surgery. The postoperational examination was performed at 2, 5, 7, 15, 22, and 30 days following the surgery. Portal vein thrombosis was defined as the obstruction of more than 50% of the vascular lumen by a thrombus in the main portal vein, its large branches, or in the splenic vein. No patient had a diagnosed PVT prior to the operation. Then the samples were divided into 2 groups, including PVT group and non-PVT group.

d-Dimer and P-Selectin Determinations

Peripheral venous blood sample (15 mL) was collected from each patient who had fasted for at least 12 hours and mixed with 3.8% sodium citrate (ratio 9:1). Sample was centrifuged for 10 minutes at 2000g, and the supernatant was stored at −80°C until use. d-Dimer and P-selectin were measured by automated latex enhanced immunoassay in citrated plasma on instrumentation Laboratory (Coagulation Systems ACL 9000) and quantified using enzyme linked immunosorbent assay kits (ZhongShan Biotech, Beijing, China). d-Dimer, P-selectin, and platelet count were tested 1 day before surgery, the second test was performed in 1 day after surgery. Thereafter, in 3, 7, and 15 days after surgery, the test was performed again.

Surgical Technique

The surgical technique was applied as described by Zong et al.¹¹ The same operative setup and standardized technique were applied for all patients. Procedures were performed by the same team of specialists in gastrointestinal and hepatobiliary surgery.

Statistics Analysis

All statistical analyses were performed using SPSS15.0 software (SPSS, Chicago, Illinois). Continuous data were expressed as mean values ± standard deviations. Significant differences between groups were determined by chi-square analysis and unpaired Student t test. Dichotomous variables were created out of continuous variables by using clinically important cutoff points. Receiver–operating characteristic (ROC) curves, sensitivity (Sen), specificity (Spe), and positive and negative predictive values (PPV and NPV) were determined to assess the diagnostic value of d-dimer, P-selectin, and platelet count. P values <.05 were considered statistically significant.

Results

Baseline Characteristics

The DU examination showed 38 patients developed PVT postoperatively (38 of 137, 27.7%), the occurrence of PVT was 5.72 ± 1.73 days after devascularization, and 86.8% of PVT (33 of 38) occurred between days 3 and 7.

There were no significant difference between the PVT group and the non-PVT group of the preoperative database including age, gender, Child-Pugh score, blood routine tests, biochemical tests, the level of D-dimer and P-selectin, mean operative time, intraoperative blood loss, and intraoperative freedom portal vein pressure (P > .05; Table 2). The 2 groups were well balanced in the distribution of pre- and intraoperational characteristics.

Table 2.

The Level of d-Dimer, P-Selectin, and Platelet Count Pre-/Postoperation.

	d-Dimer, ng/mL	P-selectin, ng/mL	Platelet Count, ×10⁹/L
PVT (n = 38)
Pre-1	230.6 ± 58.4	29.1 ± 7.2	49.6 ± 11.5
Post-1	793.5 ± 65.8	77.2 ± 6.8	76.7 ± 32.3
Post-3	941.0 ± 67.2	106.7 ± 8.3	289.6 ± 27.9
Post-7	892.5 ± 82.5	97.3 ± 7.1	376.4 ± 31.5
Post-15	737.3 ± 59.5	47.9 ± 5.2	389.9 ± 26.3
Non-PVT (n = 99)
Pre-1	218.2 ± 68.3	30.8 ± 6.1	53.1 ± 21.6
Post-1	362.1 ± 52.9	50.8 ± 5.3	71.6 ± 18.7
Post-3	391.8 ± 83.0	59.2 ± 6.7	153.5 ± 27.2
Post-7	398.5 ± 72.4	58.3 ± 7.0	173.9 ± 25.8
Post-15	351.5 ± 63.9	44.1 ± 6.2	183.5 ± 23.4
P value	^a.206 ^b.041 ^c.018 ^d.039 ^e.048	^a.383 ^b.048 ^c.022 ^d.036 ^e.260	^a.312 ^b.296 ^c.0313 ^d.228 ^e.219

Abbreviations: PVT, portal venous thrombosis; pre, preoperation; post, postoperation;

^aComparison of the 2 groups 1 day before operation.

^bComparison of the 2 groups 1 day after operation.

^cComparison of the 2 groups 3 days after operation.

^dComparison of the 2 groups 7 days after operation.

^eComparison of the 2 groups 15 days after operation.

The Level of d-Dimer, P-Selectin, and Platelet Count

As shown in Table 2 and Figures 1 to 3, in contrast to the non-PVT group, the level of d-dimer in the PVT group was much higher significantly at 1 day, 3 days, 1 week, and 15 days after devascularization (P < .05). The similar situation could be found in testing P-selectin and platelet count. The significantly more altered was in the PVT group than in the non-PVT group postoperation (P < .05). However, in the 15 days after surgery, the difference in P-selectin between the 2 groups was not significant (P = .260),

Figure 1.

The change in P-selectin level perioperatively. PVT indicates portal venous thrombosis; Pre, preoperation; Post, postoperation.

Figure 2.

The change in d-dimer level perioperatively. PVT indicates portal venous thrombosis; Pre, preoperation; Post, postoperation.

Figure 3.

The change in platelet count perioperatively. PVT indicates portal venous thrombosis; Pre, preoperation; Post, postoperation.

Value of d-Dimer, P-Selectin, and Platelet Count on PVT

By using the change in d-dimer level, P-selectin level, and platelet count as the diagnostic standard for PVT in patients with liver cirrhosis after devascularization, we achieved the Sen, Spe, PPV, and NPV in predicting PVT incidence (Table 3). It was shown that the highest Sen of the 3 markers for PVT was d-dimer, the highest Spe belonged to P-selectin. Based on the different changes in d-dimer, P-selectin, platelet count levels, and the false positive rates and Sen rates under different d-dimer, P-selectin, and platelet count levels, a ROC curve was plotted. Using the ROC analysis, the area under the ROC curve was 0.826, 0.869, and 0.705, respectively. When the 3 markers were combined to be used to diagnose PVT, the Sen was increased to 0.907, with a slight drop of Spe to 0.693, and the area under the ROC curve was 0.927(Figure 4).

Table 3.

Evaluation of the value of d-Dimer, P-selectin, and Platelet Count for PVT.^a

	Cutoff Value	Sen	Spe	PPV	NPV	AUC
d-Dimer	500 ng/mL	0.838	0.760	0.813	0.807	0.826
P-selectin	80 ng/mL	0.793	0.906	0.919	0.763	0.869
Platelet count	300 × 10⁹/L	0.695	0.702	0.731	0.668	0.705
Combination	–	0.907	0.693	0.716	0.893	0.927

Abbreviations: Sen, sensitivity; Spe, specificity; PPV, positive predictive value; NPV, negative predictive value; AUC, area under the receiver operating characteristics curve; PVT, portal vein thrombosis.

^aCombination, combined d-Dimer, P-selection, and platelet count.

Figure 4.

The receiver–operating characteristic (ROC) curve for diagnosis of portal venous thrombosis (PVT) by d-dimer, P-selectin, and platelet count.

Discussion

The prevalence of PVT in cirrhotic PHT had been reported as values ranging from 0.6% to 2.1%¹³ However, PVT has been recognized as a potential complication following devascularization for PHT, some literature showed a frequency from 6.3% to 39.0% for postoperation of PVT.^1,2 In our study, the incidence of PVT after devascularization was 8.6%. Portal vein thrombosis is often an occasional diagnosis in asymptomatic patients, but it may rapidly progress leading to massive thrombosis of intestinal veins, even fatal consequences.¹⁴ Therefore, early diagnosis of PVT may be useful to prevent uneventful outcome. The early predictive indicator of postoperative PVT may be the most focus.

At present, some methods were performed to prevent the occurrence of PVT: (1) systemic or topical injection heparin for prophylaxis intraoperatively or immediate postoperatively.¹⁵ But not all patients may have PVT or accept the treatment of injection heparin; (2) anticoagulant therapy base on the testing platelet count, since this method reflects only the number of platelets and ignores the function of platelet count. Some reports showed that the level of platelet count was not more than the level of 500 × 10⁹/L until PVT formation¹⁶; and (3) imaging examination especially DU can provide information on the thromboses via echo analysis, detect the presence of poststenotic dilatation, as well as flow defects and turbulence. Although PVT can be accurately diagnosed by DU, the formation of thrombosis was a dynamic process, only when the appearance of PVT, the ultrasound can play a valuable role, so it can’t predict thrombosis.

d-Dimer is a small peptide fragments of early thrombosis in the role of fibrinogen degradation of plasmin formation, the presence of secondary fiber in vivo dissolved and specific marker of thrombosis.¹⁷ Risch et al thought that d-dimer could be used as a diagnostic specificity of acute deep vein thrombosis indicators.¹⁸ Palareti et al found the change in d-dimer level after anticoagulation therapy for patients may predict the risk of thrombosis recurrence.¹⁹ In recent years, some studies have shown that d-dimer level as sensitive indicator for coagulation system and fibrinolytic system could predict the formation of PVT.²⁰ Our study showed that the specificity of d-dimer was 77.3% in predicting PVT incidence, the sensitivity was 84.6%, and it may be regarded as a stable and good indicator. Increased d-dimer after operation suggested that activation of coagulation in vivo and hepatic clearance of tissue plasminogen activator were related to the reduction in fibrinolysis inhibitor protein synthesis.

The study on deep venous thrombosis showed that P-selectin involved in platelet/endothelial cell adhesion and inflammation in vascular wall, which may lead to a new pathogenesis of venous thrombosis.²¹ Blenn et al found that soluble P-selectin level in patients with deep vein thrombosis was significantly higher, which may be related to excessive platelet activation.²² Myers experiment showed that P-selectin could enlarge the effect of vein wall inflammation caused by thrombotic stimuli and promoting venous thrombosis. The higher level P-selectin, the more inflammatory cells in vein wall, the bigger intravenous clot generated simultaneously in model mice.²³ Therefore, as an indicator of the degree or function of platelet activation, P-selectin can be regarded as a marker to evaluate the prothrombotic state, coagulation tendency, and formation of thrombosis in vivo. Our study showed that compared with non-PVT group, the level of P-selectin was higher in the PVT group postoperationally, especially in 3 days after surgery. When 80 ng/mL was set as a cutoff point, P-selectin had an 87% sensitivity and specificity for PVT.

As a dynamic process, the formation of thrombosis was monitored by our DU continuously. And the 3 indicators including d-dimer, P-selectin, and platelet count were tested continuously too for assessing the predictive ability. The DU examination showed the occurrence of PVT was 5.72 ± 1.73 days (2-7 days) after devascularization. The 3 indicators showed significant difference between PVT group and non-PVT group in 1, 3, and 7 days after operation (P < .05); however, the differences could not be found in the 15 days postoperatively. By this token, the best prediction PVT critical point should be set as early as possible and should be lasted 3 days at least. From the ROC curve figure, the area under the curve of P-selectin was the biggest, which of platelet count was the smallest. When the 3 indicators were combined together, the area may be up to 0.927, the value of early prediction can be improved. Then clinical interventions can be performed in time and safely.

Conclusion

Footnotes

Authors’ Note

Yang Fei and Guang-quan Zong are co-first author. They are equal contributors to this study.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

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