Neil Osterweil

November 14, 2016

BOSTON — Candidates for liver transplantation who are at risk for portal vein thrombosis can be identified with a simple risk model, allowing clinicians to start them on thromboprophylaxis, according to a large database study.

"We looked at patients waiting for liver transplantation who did not have portal vein thrombosis to see what risk factors predicted the development" of a clot in the portal vein, said Abdul Haseeb, MD, MPH, a second-year fellow in gastroenterology, hepatology, and nutrition at the University of Utah School of Medicine in Salt Lake City.

The researchers found that just four variables are strongly predictive of subsequent portal vein thrombosis risk, and the resulting risk score can be used to classify patients as being at low or high risk.

The condition affects an estimated 5% to 16% of patients undergoing evaluation for liver transplantation, and is associated with operative complications and poor clinical outcomes.

"Clinical presentation of portal vein thrombosis can range from a silent finding to a syndrome that includes abdominal pain, gastrointestinal bleeding, lactic acidosis, sepsis, nausea, and vomiting," Dr Haseeb explained.

The consequences of a small portal vein thrombosis can be minor, but an extensive thrombosis can be a contraindication for transplantation, he said.

Dr Haseeb presented results from the study during a briefing here at The Liver Meeting 2016.

Risk Prediction Model

Dr Haseeb and his colleagues assessed 891 patients with decompensated cirrhosis on the waiting list for liver transplantation who underwent serial ultrasound or other cross-sectional imaging of portal and hepatic vessels from 1987 to 2014.

They divided the group into a derivation cohort of 621 patients (70%) and a validation cohort of 270 patients (30%).

On univariate analysis, the researchers narrowed the 34 variables they considered down to nine independent variables. They then created multivariate regression models and, using the beta coefficients for each variable from the final regression model, created a risk score for portal vein thrombosis with just four variables.

They tested their creation — which they called the Intermountain PVT Risk Score — in the validation cohort.

The four variables determined to be predictive of portal vein thrombosis are a history of bacterial peritonitis, a history of esophageal and/or gastric varices, and, at the time the patient is added to the waiting list, hepatic encephalopathy and a bilirubin level above 4.5 mg/dL.

All variables were assigned 1 point except bilirubin, which was assigned 2 points.

Each patient could have a risk score from 0 to 5, with 5 indicating the highest risk for portal vein thrombosis. A risk score above 3 is associated with a 15-fold risk, Dr Haseeb reported.

Table. Variables Predictive of Portal Vein Thrombosis

Variable Hazard Ratio 95% Confidence Interval P Value
History of bacterial peritonitis 2.58 1.09–6.13 .032
History of esophageal or gastric varices 2.88 1.66–5.00 <.001
Hepatic encephalopathy at list 2.74 1.03–7.34 .044
Bilirubin >4.50 mg/dL at list 3.87 1.96–7.61 <.001

 

In both the derivation and validation cohorts, the negative predictive value was higher when the risk score was 3 or higher than when the risk score was 2 or lower (94.3% vs 92.3%).

Prospective studies are needed to determine whether interventions on the basis of risk score, such as anticoagulation therapy with warfarin or low-molecular-weight heparin, will reduce the frequency of portal vein thrombosis and improve outcomes for patients on the waiting list, Dr Haseeb noted.

The risk score might have more research value than clinical utility, said Mordechai Rabinovitz, MD, from the division of gastroenterology, hepatology, and nutrition at the University of Pittsburgh Medical Center, who was not involved in the study.

"Everyone who's going for a transplant is being evaluated closely. Everyone has CT scans, MRI, ultrasound, so if any patients have a portal vein thrombosis, we know about it in advance," he told Medscape Medical News.

"There are many times when the transplant evaluation was done a year or 2 before," Dr Rabinovitz explained. "Let's say today they find a liver for a patient. Everything that was done then doesn't apply to today, so you need to repeat the tests. This is nice academically, but before transplant, you need to prove if the patient has a portal vein thrombosis or not."

The study funding source was not disclosed. Dr Haseeb and Dr Rabinovitz have disclosed no relevant financial relationships.

The Liver Meeting 2016: American Association for the Study of Liver Diseases (AASLD): Abstract 238. Presented November 14, 2016.

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