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The purpose of this study was to assess the safety and feasibility of sequential hypothermic oxygenated perfusion and normothermic machine perfusion and the potential benefits of graft viability preservation and assessment before liver transplantation.With the Food and Drug Administration and institutional review board approval, 17 expanded criteria donor livers underwent sequential hypothermic oxygenated perfusion and normothermic machine perfusion using our institutionally developed perfusion device.Expanded criteria donor livers were from older donors, donors after cardiac death, with steatosis, hypertransaminasemia, or calcified arteries. Perfusion duration ranged between 1 and 2 hours for the hypothermic oxygenated perfusion phase and between 4 and 9 hours for the normothermic machine perfusion phase. Three livers were judged to be untransplantable during normothermic machine perfusion based on perfusate lactate, bile production, and macro-appearance. One liver was not transplanted because of recipient issue after anesthesia induction and failed reallocation. Thirteen livers were transplanted, including 9 donors after cardiac death livers (donor warm ischemia time 16-25 minutes) and 4 from donors after brain death. All livers had the standardized lactate clearance60% (perfusate lactate cleared to4.0 mmol/L) within 3 hours of normothermic machine perfusion. Bile production rate was 0.2 to 10.7 mL/h for donors after brain death livers and 0.3 to 6.1 mL/h for donors after cardiac death livers. After transplantation, 5 cases had early allograft dysfunction (3 donors after cardiac death and 2 donors after brain death livers). No graft failure or patient death has occurred during follow-up time of 6 to 13 months. Two livers developed ischemic cholangiopathy. Compared with our previous normothermic machine perfusion study, the bile duct had fewer inflammatory cells in histology, but the post-transplant outcomes had no difference.Sequential hypothermic oxygenated perfusion and normothermic machine perfusion preservation is safe and feasible and has the potential benefits of preserving and evaluating expanded criteria donor livers.

Purpose To show an alternative surgical technique for the introduction of the intravitreal fluocinolone acetonide (FAc) implant (Iluvien®) into the vitreous cavity using a 23-gauge (G) trocar if it is retained during its implantation in the subconjunctival space. Methods We describe the surgical procedure performed to solve the complication: The FAc implant was extracted from the subconjunctival space using flat retinal forceps. A 23-G trocar was inserted 3,5 mm to the limbus. The same flat retinal forceps were used to take the FAc implant and introduce it into the vitreous cavity using a 23-G trocar. Results The patient's best corrected visual acuity (BCVA) (Snellen) improved from 20/200 to 20/63 and the central macular thickness (CMT) was reduced from 610 microns (µm) to 215 µm after one week of the FAc implantation. He remained stable after 3 months of follow-up, with a BCVA of 20/63 and a CMT of 191 µm. His intraocular pressure (IOP) remained stable and the integrity of the implant was checked by indirect ophthalmoscopy. Conclusion The introduction of the intravitreal FAc implant using a 23-gauge trocar constitutes a valid alternative if it is retained during its implantation in the subconjunctival space. The functionality of the implant remained intact in our patient.

Living donor liver transplantation (LDLT) using small grafts, especially left lobe grafts (H1234-MHV) (LLG), continues to be a challenge due to small-for-size syndrome (SFSS). We herein demonstrate that with surgical modifications, outcomes with small grafts can be improved.Between 2012 and 2020, we performed 130 adult LDLT using 61 (47%) LLG (H1234-MHV) in a single Enterprise. The median graft-to-recipient weight ratio was 0.84%, with graft-to-recipient weight ratio0.7% accounting for 22%. Splenectomy was performed in 72 (56%) patients for inflow modulation before (n=50) or after (n=22) graft reperfusion. In LLG-LDLT, venous outflow was achieved using all three recipient hepatic veins. In right lobe graft (H5678) (RLG)-LDLT, the augmented graft right hepatic vein was anastomosed to the recipient's cava with a large cavotomy. Outcome measures include SFSS, early allograft dysfunction (EAD), and survival.Graft survival rates at 1, 3, and 5 years were 94%, 90%, and 83%, respectively, with no differences between LLG (H1234-MHV) and RLG (H5678). Splenectomy significantly reduced portal flow without increasing the complication rate. Despite the aggressive use of small grafts, SFSS and EAD developed in only 1 (0.8%) and 18 (13.8%) patients, respectively. Multivariable logistic regression revealed model for end-stage liver disease score and LLG (H1234-MHV) as independent risk factors for EAD and splenectomy as a protective factor (odds ratio: 0.09; P =0.03). For LLG (H1234-MHV)-LDLT, patients who underwent prereperfusion splenectomy tended to have better 1-year graft survival than those receiving postreperfusion splenectomy.LLG (H1234-MHV) are feasible in adult LDLT with excellent outcomes comparable to RLG (H5678). Venous outflow augmentation and splenectomy help lower the threshold of using small-for-size grafts without compromising graft survival.

The persistent shortage of liver allografts contributes to significant waitlist mortality despite efforts to increase organ donation. Normothermic machine perfusion holds the potential to enhance graft preservation, extend viability, and allow liver function evaluation in organs previously discarded because considered too high-risk for transplant.Discarded livers from other transplant centers were transplanted after assessment and reconditioning with our institutionally developed normothermic machine perfusion device. We report here our preliminary data.Twenty-one human livers declined for transplantation were enrolled for assessment with normothermic machine perfusion. Six livers (28.5%) were ultimately discarded after normothermic machine perfusion because of insufficient lactate clearance (4.1 mmol/L after 4 hours), limited bile production (0.5 mI/h), or moderate macrosteatosis, whereas 15 (71.5%) were considered suitable for transplantation. Normothermic machine perfusion duration was from 3 hours, 49 minutes to 10 hours, 29 minutes without technical problems or adverse events. No intraoperative or major early postoperative complications occurred in all transplanted recipients. No primary nonfunction occurred after transplantation. Seven livers had early allograft dysfunction with fast recovery, and 1 patient developed ischemic cholangiopathy after 4 months treated with biliary stents. All other patients had good liver function with a follow-up time of 8 weeks to 14 months.In total, 71.5% of discarded livers subjected to ex vivo normothermic machine perfusion were successfully transplanted after organ perfusion and assessment using an institutionally built device. This study challenges the current viability criteria reported in the literature and calls for a standardization of viability markers collection, an essential condition for the advancement of the field.

OBJECTIVE: This paper examines the incidence, clinical presentation, and pathophysiology of portal vein thrombosis (PVT) in cirrhosis. Additionally, we have reviewed the literature regarding the current status of medical and interventional radiology management of PVT and have proposed a novel algorithm for the management given different clinical scenarios. Lastly two representative cases displaying endovascular treatment options are provided. BACKGROUND: Portal vein thrombus in the setting of cirrhosis is an increasingly recognized clinical issue with debate on its pathophysiology, natural course, and optimal treatment. Approximately one-third of patients are asymptomatic, and detection of the thrombus is an incidental finding on imaging performed for other reasons. In 30% to 50% of patients, PVT resolves spontaneously. However, there is increased post-transplant mortality in patients with completely occlusive PVT, therefore effective early revascularization strategies are needed for patients with complete PVT who are expected to undergo liver transplant. Additionally, no consensus has been reached regarding PVT treatment in terms of timing and type of interventions as well as type and duration of anticoagulation. METHODS: Computerized literature search as well as discussion with experts in the field. CONCLUSIONS: Management of PVT is complex, as many variables affect which treatments can be used. Anticoagulation appears to be the optimal first-line treatment in patients with acute PVT but without bleeding varices or mesenteric ischemia. Minimally invasive treatments include various methods of mechanical thrombectomy, chemical thrombolysis, and transjugular intrahepatic portosystemic shunt (TIPS) placement with or without variceal embolization. Definitive recommendations are difficult due to lack of high quality data and continued research is needed to evaluate the efficacy of different anticoagulants as well as the timing and use of various minimally invasive therapies in specific circumstances.

Cardiovascular events have a major impact on overall outcomes after liver transplantation. Today's transplant patients are older than those in the past and therefore are more likely to have coexisting cardiac comorbidities. In addition, pathophysiologic effects of advanced liver disease on the circulatory system pose challenges in perioperative management. This review discusses important preoperative, intraoperative, and postoperative cardiac considerations in patients undergoing liver transplant.

Introduction Diffuse splanchnic vein thrombosis (DSVT) remains a serious challenge in liver transplantation (LT). Reno-portal anastomosis (RPA) has previously been reported as a valid option for management of patients with DSVT during LT. The aim of this study was to evaluate posttransplant renal function and surgical outcomes of patients with DSVT who underwent RPA during LT. Methods Between January 2005 and December 2017, 1,270 patients underwent LT at our institution, including 16 with DSVT managed with RPA (RPA group). We compared renal function and surgical outcomes in these patients to outcomes in 48 propensity-score (PS) matched patients without thrombosis (control group), using a 1:3 matching model. Results The two groups had similar rates of postoperative portal vein thrombosis (PVT), renal dysfunction as measured by estimated glomerular filtration rate (eGFR), and overall postoperative complications (Clavien grade III), although the RPA group had a higher incidence of postoperative upper gastrointestinal (GI) bleeding (31.3% vs 4.2%; p=0.009) that had no clinical consequence. There were no significant differences in five-year graft and patient survival rates between the groups (p=0.133 and p=0.166, respectively). Conclusion RPA is an established technique in the management of patients with DSVT during LT, with comparable outcomes to patients without thrombosis. Our report is the first to demonstrate similar surgical outcomes, including long-term renal function, in LT recipients with or without RPA.

Background Calcineurin inhibitor (CNI) based immunosuppression in liver transplantation (LTx) is associated with acute and chronic deterioration of kidney function. Delaying CNI initiation by using induction rabbit anti-thymocyte globulin (rATG) may provide kidneys with adequate time to recover from a perioperative insult reducing the risk of early post-LTx renal deterioration. Methods This was an open-label, multicenter, randomized controlled clinical trial comparing use of induction rATG with delayed CNI initiation (day-10) against upfront CNI commencement (SOC; standard of care) in those patients deemed at standard risk of postoperative renal dysfunction following LTx. The primary end point was change in (delta) creatinine from baseline to month-12. Results Fifty-five patients were enrolled in each study arm. Mean Tacrolimus levels remained comparable in both groups from day-10 throughout the study period. A significant difference in delta creatinine was observed between rATG and SOC groups at 9-months (p=0.03) but not at month-12 (p=0.05). eGFR levels remained comparable between cohorts at all time points. Rates of biopsy-proven acute rejection at 1-year were similar between groups (16.3 vs 12.7%, p= 0.58). rATG showed no significant adverse effects. Survival at 12-months was comparable between groups (p= 0.48). Conclusions Although the use of induction rATG and concurrent CNI deferral in this study did not demonstrate a significant difference in delta creatinine at 1 year, these results indicate a potential role for rATG in preserving early kidney function, especially when considered with CNI deferral beyond 10 days and/or lower target Tacrolimus levels, with acceptable safety and treatment efficacy.

The use of livers from donation after circulatory death (DCD) is historically characterized by increased rates of biliary complications and inferior short-term graft survival (GS) compared to donation after brain death (DBD) allografts. This study aimed to evaluate the dynamic prognostic impact of DCD livers to reveal whether they remain an adverse factor even after patients survive a certain period following liver transplant (LT). This study used 74 961 LT patients including 4065 DCD LT in the scientific registry of transplant recipients from 2002-2017. The actual, 1 and 3-year conditional hazard ratio (HR) of 1-year GS in DCD LT were calculated using a conditional version of Cox regression model. The actual 1-, 3-, and 5-year GS of DCD LT recipients were 83.3%, 73.3%, and 66.3%, which were significantly worse than those of DBD (all P

Late vena cava/hepatic outflow obstruction after orthotopic liver transplantation (OLT), while rare, is among the most challenging complications. The cause may be an organized thrombus, reactive edema, fibrosis/scarring with calcification, or neointimal hyperplasia. Moreover, the obstruction can involve different anatomical parts of the vena cava. Surgical approaches have classically included anastomotic revision, hepatopexy, thrombectomy, cavoatrial shunt, and retransplantation. We present a case report of an innovative approach to combined inferior vena cava (IVC)/hepatic outflow obstruction in a 62-year-old female who underwent OLT using a piggyback technique for end-stage liver disease secondary to hepatitis C virus and alcohol, approximately 10 months post-transplant. A right atrial approach and hypothermic circulatory (cardiac) arrest were employed. The IVC stricture was easily resolved by performing a side to side cavo-cavostomy using an endovascular stapler (endo-GIA). In conclusion, this innovative approach is safe and effective in resolving severe outflow obstruction after liver transplantation.

Summary: Intravascular ultrasound (IVUS) has been used extensively in coronary applications. Its use in venous applications has increased as endovascular therapy has increasingly become the mainstay therapy for central venous diseases. IVUS has been used for both diagnostic and therapeutic purposes in managing venous stenotic disease, venous occlusive disease, and IVC filter placement and removal. IVUS has been proven to be effective in providing detailed measurement of the venous anatomy, which aid in determining the appropriate size and the approach for venous stent placement. In IVC filter placement, IVUS can provide detailed measurement and guide IVC filter placement in emergent and critical care settings. It also has certain utility in filter removal. At any rate, to date there are only a few studies examining its impact on patient outcomes. Prospective randomized controlled trials are warranted in the future.

Neuroendocrine tumor (NET) metastasis localized to the liver is an accepted indication for liver transplantation as such tumors have a low biological aggressiveness in terms of malignancy and are slow growing. Moreover, the long-term results are comparable with and in some cases even better than those of transplantations performed for primary liver cancer. However, compared with nonmalignant conditions, neuroendocrine liver metastasis (NELM) may result in an inferior outcome of transplantation. In the face of the scarcity of donated organs and recent improved results of non-surgical treatment for NELM, controversy over patient selection and timing for liver transplantation continues. In this review, we provide an overview of the diagnostic workup and selection criteria of patients with NELM being considered for liver transplantation. Thereafter, we provide a critical analysis of the reported outcomes of orthotopic liver transplantation.

Transjugular intrahepatic portosystemic shunt has been established as an effective treatment for complicated portal hypertension. This retrospective study investigated the effect of pretransplant transjugular intrahepatic portosystemic shunt placement on intraoperative graft hemodynamics and surgical outcomes after liver transplantation.Of 1,081 patients who underwent liver transplantation between January 2007 and June 2017 at Cleveland Clinic (OH, USA), 130 patients had transjugular intrahepatic portosystemic shunt placement before liver transplant. We performed a 1:2 propensity score matching to compare intraoperative graft hemodynamics and surgical outcomes between the transjugular intrahepatic portosystemic shunt group (n = 130) and the no-transjugular intrahepatic portosystemic shunt group (n = 260).The transjugular intrahepatic portosystemic shunt did not increase operative time, the volume of blood transfusion, duration of hospital stay, or complication rates. Graft and patient survivals were similar between the groups. Mean intraoperative cardiac output and graft portal flow in the transjugular intrahepatic portosystemic shunt group were greater than in the no-transjugular intrahepatic portosystemic shunt group (P = .03 and P = .003, respectively). In multivariate analysis, male sex, younger age, low platelet count, absence of portal vein thrombosis, and pretransplant transjugular intrahepatic portosystemic shunt placement were independently associated with increased portal flow volume (Por = 0.03 each). Transjugular intrahepatic portosystemic shunt malposition was observed in 17 patients (13.1%). The 1-year patient survival was 70.6% with transjugular intrahepatic portosystemic shunt malposition and 92.0% without transjugular intrahepatic portosystemic shunt malposition (P = .01).Our findings suggest that pretransplant transjugular intrahepatic portosystemic shunt placement increases graft portal flow but does not compromise surgical outcomes after liver transplantation. Transjugular intrahepatic portosystemic shunt malposition, however, is not uncommon and may increase the complexity of transplantation.

Normothermic machine perfusion provides continuous perfusion to ex situ hepatic grafts through the portal vein and the hepatic artery. Because the portal vein has high flow with low pressure and the hepatic artery has low flow with high pressure, different types of perfusion machines have been employed to match the two vessels' infusion hemodynamics.We compared transplanted human livers perfused through a 2-pump (n = 9) versus a 1-pump perfusion system (n = 6) where a C-clamp is used as a tubing constrictor to regulate hemodynamics.There was no significant difference between groups in portal vein or hepatic artery flow rate. The 1-pump group had more hemoglobin in the perfusate. However, there was no significant difference in plasma hemoglobin between the 2-pump and 1-pump groups at each time point or in the change in levels, proving no hemolysis occurred due to C-clamp tube constriction. After transplantation, the 2-pump group had two cases of early allograft dysfunction (EAD), whereas the 1-pump group had no EAD. There was no graft failure or patient death in either group during follow-up ranging from 20-52 months.Our data show that the 1-pump design provided the same hemodynamic output as the 2-pump design, with no additional hemolytic risk, but with the benefits of lower costs, easier transport and faster and simpler setting.

A recent study using US national registry data reported, using Cox proportional hazards (PH) models, that split-liver transplantation (SLT) has improved over time and is no more hazardous than whole-liver transplantation (WLT). However, the study methods violated the PH assumption, which is the fundamental assumption of Cox modeling. As a result, the reported hazard ratios (HRs) are biased and unreliable. This study aimed to investigate whether the risk of graft survival (GS) in SLT has really improved over time, ensuring attention to the PH assumption. This study included 80,998 adult deceased donor liver transplantation (LT) (1998-2015) from the Scientific Registry Transplant Recipient. The study period was divided into 3 time periods: era 1 (January 1998 to February 2002), era 2 (March 2002 to December 2008), and era 3 (January 2009 to December 2015). The PH assumption was tested using Schoenfeld's test, and where the HR of SLT violated the assumption, changes in risk for SLT over time from transplant were assessed. SLT was performed in 1098 (1.4%) patients, whereas WLT was used in 79,900 patients. In the Cox PH analysis, the P values of Schoenfeld's global tests were

Donation after circulatory death (DCD) liver transplantation improves deceased donor liver use and decreases waitlist burden, albeit at an increased risk of biliary complications and inferior graft survival. Employing liver vascular inflow measurements intraoperatively permits allograft prognostication. However, its use in DCD liver transplantation is hitherto largely unknown and further explored here. DCD liver transplantation patient records at a single center from 2005 to 2018 were retrospectively scrutinized. Intraoperative flow data and relevant donor parameters were analyzed against endpoints of biliary events and graft survival. A total of 138 cases were chosen. The incidence of cumulative biliary complications was 38%, the majority of which were anastomotic strictures and managed successfully by endoscopic means. The ischemic cholangiopathy rate was 6%. At median thresholds of a portal vein (PV) flow rate of92 mL/minute/100 g and buffer capacity (BC) of0.04, both variables were independently associated with risk of biliary events (P = 0.01 and 0.04, respectively). Graft survival was 90% at 12 months and 75% at 5 years. Cox regression analysis revealed a PV flow rate of50 mL/minute/100 g as predictive of poorer graft survival (P = 0.01). Furthermore, 126 of these DCD livers were analyzed against a propensity-matched group of 378 contemporaneous donation after brain death liver allografts (1:3), revealing significantly higher rates (P 0.001) of both early allograft dysfunction (70% versus 30%) and biliary complications (37% versus 20%) in the former group. Although flow data were comparable between both sets, PV flow and BC were predictive of biliary events only in the DCD cohort. Intraoperative inflow measurements therefore provide valuable prognostication on biliary/graft outcomes in DCD liver transplantation, can help inform graft surveillance, and its routine use is recommended.

Objective To evaluate the short- and long-term outcomes of renoportal anastomosis (RPA) in a large multicentric series. Summary background The current knowledge on RPA for portal reconstruction during liver transplantation (LT) in patients with diffuse portal vein thrombosis (PVT) and a large splenorenal shunt (SRS) is poor and limited to case reports and small case series. Methods All consecutive LTs with RPA performed in 5 centers between 1998 and 2020 were included. RPA was physiological provided it drained the splanchnic venous return through a large SRS (≥1 cm diameter). Complications of portal hypertension (PHT), long-term RPA patency, and patient and graft survival were assessed. RPA success was achieved provided the 3 following criteria were all fulfilled: patients were alive with patent RPA and without clinical PHT. Results RPA was attempted and feasible in 57 consecutive patients and was physiological in 51 patients (89.5%). Ninety-day mortality occurred in 5 (8.5%) patients, and PHT-related complications occurred in 42.9% of patients. With a median follow-up of 63 months, the 1-, 3- and 5-year patient and graft survival rates were 87%, 83%, and 76% and 82%, 80%, and 73%, respectively. The primary and primary-assisted patency rates at 5 years were 84.5% and 94.3%, respectively. Success was achieved in 90% (27/30) of patients with a follow-up ≥ 5 years. Conclusions Despite a high rate of PHT-related complications, excellent long-term patient and graft survival could be achieved. RPA could be considered successful in the vast majority of patients. The expanded use of RPA is warranted.

Laparoscopic liver resection (LLR) has significantly evolved over the last two decades through improvements in approach, technique, and instrumentation and offers benefits over open liver surgery in terms of quicker recovery, early return to normal life, and cosmesis.1 However, the associated technical complexity of LLR coupled with overarching emphasis on donor safety have been the primary reasons for its delayed introduction into the domain of living liver donation.

BACKGROUND Rates of withdrawal of life-sustaining treatment are higher among critically ill pediatric patients compared to adults. Therefore, livers from pediatric donation after circulatory death (pDCD) could improve graft organ shortage and waiting time for listed patients. As knowledge on the utilization of pDCD is limited, this study used US national registry data (2002-2017) to estimate the prognostic impact of pDCD in both adult and pediatric liver transplant (LT). METHODS In adult LT, the short-term (1-year) and long-term (overall) graft survival (GS) between pDCD and adult donation after circulatory death (aDCD) grafts was compared. In pediatric LT, the short- and long-term prognostic outcomes of pDCD were compared with other type of grafts (brain dead, split, and living donor). RESULTS Of 80 843 LTs in the study, 8967 (11.1%) were from pediatric donors. Among these, only 443 were pDCD, which were utilized mainly in adult recipients (91.9%). In adult recipients, short- and long-term GS did not differ significantly between pDCD and aDCD grafts (hazard ratio = 0.82 in short term and 0.73 in long term, both P > 0.05, respectively). Even "very young" (≤12 y) pDCD grafts had similar GS to aDCD grafts, although the rate of graft loss from vascular complications was higher in the former (14.0% versus 3.6%, P < 0.01). In pediatric recipients, pDCD grafts showed similar GS with other graft types whereas waiting time for DCD livers was significantly shorter (36.5 d versus 53.0 d, P < 0.01). CONCLUSIONS Given the comparable survival seen to aDCDs, this data show that there is still much scope to improve the utilization of pDCD liver grafts.

Although experimental studies have reported that hepatic ischemia-reperfusion injury promotes tumor growth and metastases, the impact of graft hemodynamics on the recurrence of hepatocellular carcinoma (HCC) after liver transplantation (LT) is unclear. To investigate the association between graft hemodynamics and HCC recurrence after LT, we conducted a retrospective analysis of 279 patients who underwent LT for HCC. Graft hemodynamics including portal vein flow (PVF), hepatic artery flow (HAF), and total hepatic flow (THF) was analyzed as a predictor of HCC recurrence, using competing risk regression analyses. The cutoff values of PVF, HAF, and THF were set at the lower quartile of distribution. A cumulative recurrence curve demonstrated that low THF (

BACKGROUND Dobutamine stress echocardiography (DSE) is commonly used for cardiovascular assessment before orthotopic liver transplantation (OLT). The coronary artery calcium score (CACS) is a useful screening tool for coronary artery disease (CAD). We aimed to compare the sensitivity and specificity of DSE and CACS for CAD in OLT candidates. MATERIAL AND METHODS A total of 265 of the 1589 patients who underwent OLT at our center between 2008 and 2019 had preoperative coronary angiography (CAG). Of these, 173 had DSE and 133 had a CT scan suitable for CACS calculation within 1 year of OLT. Patients with a nondiagnostic DSE were excluded (n=100). Two reviewers evaluated CACS on CT scans. The sensitivity/specificity of DSE and CACS for detection of angiographically significant CAD were calculated for patients with both tests (n=36). A separate analysis compared the sensitivity/specificity of a diagnostic DSE (n=73) and CACS (n=133) against CAG for all patients with either test. RESULTS Sensitivity and specificity were 57.1% and 89.7%, respectively, for DSE, compared with 71.4% and 62.1% for CACS at ≥100 Agatston score. For the analysis of all patients with either test, the sensitivity/specificity of DSE for detection of CAD and CACS were 30.8% and 85.0% and 80.0% and 62.8%, respectively. On ROC analysis, CACS was a satisfactory predictor of obstructive CAD (AUC, 0.76±0.06, 95% CI, 0.66-0.87; P0.001). CONCLUSIONS CACS may be an important tool for cardiovascular assessment in patients undergoing OLT. DSE was nondiagnostic in a large percentage of OLT candidates, limiting its use in this population.