PubMed Health⌕ Search

Biomedical subjects

Anna S F Lok

Publications and source records attributed to Anna S F Lok.

At least 19 recordsLinked to original sources
PubMed2007

Comparison of clinical outcomes in chronic hepatitis B liver transplant candidates with and without hepatocellular carcinoma.

Patients with hepatocellular carcinoma (HCC) receive a higher MELD score and may undergo liver transplantation (OLT) earlier compared to patients with cirrhosis, potentially decreasing waiting list mortality. However, post-OLT survival may be reduced by recurrence of HCC. We compared clinical outcomes between patients with HBV-cirrhosis and no HCC and patients with HBV-HCC. A total of 279 patients (HBV-cirrhosis = 183; HBV-HCC = 96) in the US HBV-OLT study were followed for a median of 30.2 months from listing. Patients with HCC were older, more likely to be Asian, and had less severe liver impairment than patients with HBV-cirrhosis. Despite a higher rate of OLT in patients with HCC (78.1% vs. 51.4%; P < 0.001), intention-to-treat (ITT) survival (73% vs. 78%) and survival without OLT (82% vs. 79%) at 5 years were similar for patients with and without HCC. Cox regression analysis identified higher albumin, lower MELD, no HCC at listing, and being transplanted to be associated with better ITT survival. Ninety-four patients with HCC (including 19 new HCC) and 75 with HBV-cirrhosis underwent OLT. Post-OLT survival (83% vs. 90%) and HBV recurrence (11% vs. 10%) at 3 years were similar, while disease (HBV and/or HCC) recurrence (19% vs. 10%; P = 0.043) was higher in patients with HBV-HCC vs. HBV-cirrhosis. Disease recurrence was the only independent predictor of post-OLT survival. In conclusion, despite more advanced liver disease and a lower rate of transplantation, ITT survival of patients listed for HBV-cirrhosis was comparable to those with HBV-HCC, possibly related to beneficial effects of antiviral therapy.

Adult↗
PubMed2007

Outcomes in hepatitis C virus-infected recipients of living donor vs. deceased donor liver transplantation.

In this retrospective study of hepatitis C virus (HCV)-infected transplant recipients in the 9-center Adult to Adult Living Donor Liver Transplantation Cohort Study, graft and patient survival and the development of advanced fibrosis were compared among 181 living donor liver transplant (LDLT) recipients and 94 deceased donor liver transplant (DDLT) recipients. Overall 3-year graft and patient survival were 68% and 74% in LDLT, and 80% and 82% in DDLT, respectively. Graft survival, but not patient survival, was significantly lower for LDLT compared to DDLT (P = 0.04 and P = 0.20, respectively). Further analyses demonstrated lower graft and patient survival among the first 20 LDLT cases at each center (LDLT 20; P = 0.002 and P = 0.002, respectively) and DDLT recipients (P < 0.001 and P = 0.008, respectively). Graft and patient survival in LDLT >20 and DDLT were not significantly different (P = 0.66 and P = 0.74, respectively). Overall, 3-year graft survival for DDLT, LDLT >20, and LDLT 20 were not significantly different. Important predictors of graft loss in HCV-infected patients were limited LDLT experience, pretransplant HCC, and higher MELD at transplantation.

Adult↗
PubMed2006

A genotype-independent real-time PCR assay for quantification of hepatitis B virus DNA.

Accurate quantification of hepatitis B virus (HBV) DNA levels is important for monitoring patients with chronic HBV infection and for assessing their responses to antiviral therapy. This study aimed to develop a real-time PCR assay that is sensitive and can accurately quantify a wide range of HBV DNA levels across the known HBV genotypes. An "in-house" real-time PCR assay using primers and a TaqMan probe in a highly conserved region of the HBV surface gene was designed. The assay was standardized against a WHO standard and validated against plasmids of HBV genotypes A through H. The linear quantification range was approximately 5 x 10(0) to 2.0 x 10(9) IU/ml. Results of samples from patients infected with HBV genotypes A through H tested using our real-time "in-house" PCR assay showed an excellent correlation with those of the Cobas Amplicor HBV Monitor (R2=0.9435) and the Cobas TaqMan HBV (R2=0.9873) tests. We have established a real-time PCR assay that is genotype independent and can accurately quantify a wide range of HBV DNA levels. Further studies of additional samples are ongoing to validate the genotype independence of our assay.

DNA Primers↗
PubMed2006

Antiviral options for the treatment of chronic hepatitis B.

Hepatitis B virus (HBV) is an important cause of end-stage liver disease and hepatocellular carcinoma. Effective treatment can delay or prevent these outcomes. The decision to treat is based on the activity of liver disease and HBV replication status, and the likelihood of a long-term benefit. Approved therapies include standard and pegylated interferon-alfa and nucleoside analogues: lamivudine, adefovir and entecavir. Current therapies do not eradicate HBV so long-term treatment is usually required. Development of drug resistance is a major concern with long-term treatment. Even with successful therapy, patients remain at risk for reactivation of viral replication and require lifelong monitoring.

Adenine↗
PubMed2006

HCV RNA detection by TMA during the hepatitis C antiviral long-term treatment against cirrhosis (Halt-C) trial.

For making treatment decisions related to chronic hepatitis C, the utility of HCV RNA tests with increased sensitivity has not been defined. Prior interferon nonresponders with advanced fibrosis (n = 1,145) were retreated with peginterferon alpha-2a and ribavirin. Patients who were HCV RNA-negative by a polymerase chain reaction (PCR)-based assay (Roche COBAS Amplicor HCV Test, v. 2.0; lower limit of detection [LOD] 100 IU/mL) at week 20 (W20) received treatment for 48 weeks. Stored specimens were tested using the Bayer VERSANT HCV RNA Qualitative (TMA) Assay (LOD 9.6 IU/mL) and compared to PCR results for the ability to predict sustained virological response (SVR; defined as undetectable HCV RNA by PCR at W72). Nearly all PCR-positive samples (1006/1007, 99.9%) were positive as assessed by TMA. Among 1,294 PCR-negative samples, 22% were TMA-positive. Negative TMA results were more predictive of SVR than were negative PCR results at W12 (82% vs. 64%, P < .001) and at W20 (66% vs. 52%, P = 0.001). SVR was more likely the earlier TMA had become negative during treatment (82% at W12, 44% at W20, 20% at W24). Among 45 patients who were TMA-positive but were PCR-negative at W20 and W24, none achieved SVR (95% CI: 0%-8%). Approximately 10% of patients with a single positive TMA result at the end of treatment still achieved SVR. In conclusion, negative TMA results at or after W12 were superior to negative PCR results for predicting SVR. In patients with negative PCR results during treatment, a single positive TMA test did not exclude SVR, although persistently positive tests did.

Antiviral Agents↗
PubMed2006

Evolution of multi-drug resistant hepatitis B virus during sequential therapy.

Multi-drug resistant hepatitis B virus (HBV) has been reported in hepatitis B patients who received sequential antiviral therapy. In vitro studies showed that HBV constructs with mutations resistant to lamivudine and adefovir have marked reduction in sensitivity to combination of lamivudine and adefovir, whereas constructs with mutations resistant to either drug remain sensitive to the other drug. We conducted this study to determine whether mutations conferring resistance to multiple antiviral agents co-locate on the same HBV genome in vivo and to describe the evolution of these mutations. Sera from six patients who had been found to have multi-drug resistant HBV mutations to lamivudine+adefovir, lamivudine+hepatitis B immunoglobulin (HBIG), or lamivudine+entecavir on direct sequencing were cloned after nested polymerase chain reaction (PCR). Analysis of 215 clones from 11 samples with multi-drug resistant mutations on direct sequencing showed that 183 (85%) clones had mutations to both therapies on the same genome; 31 clones had lamivudine-resistant mutants only. Clonal analysis of serial samples from three patients showed progressive evolution from all clones with lamivudine-resistant HBV mutations only to mixtures of clones that have multi-drug resistant mutations and clones that have lamivudine-resistant HBV mutations only, and ultimately all clones having multi-drug resistant HBV mutations. In conclusion, mutations conferring resistance to multiple antiviral agents co-locate on the same viral genome, suggesting that combination therapy directed against mutants resistant to each treatment may not be adequate in suppressing multi-drug resistant HBV. De novo combination therapy may prevent the emergence of multi-drug resistant mutants.

Adult↗
PubMed2006

Impact of disease severity on outcome of antiviral therapy for chronic hepatitis C: Lessons from the HALT-C trial.

In patients with chronic hepatitis C, advanced fibrosis and cirrhosis are associated with lower rates of sustained virologic response (SVR) to interferon (IFN)-based therapy. In this study, we assessed virologic response to retreatment with peginterferon alfa-2a and ribavirin (RBV), as a function of the baseline fibrosis score (Ishak staging) and platelet count, in 1,046 patients enrolled in the Hepatitis C Antiviral Long-term Treatment against Cirrhosis (HALT-C) Trial. All patients had failed prior treatment with IFN or peginterferon +/- RBV and had Ishak fibrosis scores > or = 3. Four groups of patients with increasingly severe liver disease were compared: (A) bridging fibrosis (Ishak 3 and 4) with platelet counts >125,000/mm3 (n = 559); (B) bridging fibrosis with platelet counts < or =125,000/mm3 (n = 96); (C) cirrhosis (Ishak 5 and 6) with platelet counts >125,000/mm3 (n = 198); and (D) cirrhosis with platelet counts < or =125,000/mm3 (n = 193). SVR rates were 23%, 17%, 10%, and 9% in groups A, B, C, and D, respectively (P < .0001 for trend). Reduction in SVR as a function of increasingly severe disease was independent of age, percent African American, HCV genotype, HCV level, and type of prior therapy. Dose reduction lowered SVR frequencies, but to a lesser extent than disease severity. By logistic regression, cirrhosis (P < .0001) was the major determinant that impaired virologic response, independent of dose reduction or platelet count. In conclusion, disease severity is a major independent determinant of rate of SVR in patients with advanced chronic hepatitis C. New strategies are needed to optimize antiviral therapy in these "difficult-to-cure" patients.

Antiviral Agents↗
PubMed2006

Update on viral hepatitis: 2005.

PURPOSE OF REVIEW: This review aims to provide a concise summary of relevant developments in the treatment and prevention of viral hepatitis based on publications between December 2004 and November 2005. RECENT FINDINGS: Long-term therapy with lamivudine was shown to reduce the incidence of adverse clinical outcomes in patients with chronic hepatitis B. This benefit was, however, diminished in patients with viral breakthrough. Combination therapy (peginterferon or telbivudine plus lamivudine) decreased the risk of antiviral resistance but did not improve response compared with monotherapy. Entecavir and tenofovir were shown to be effective in suppressing lamivudine-resistant hepatitis B. A shorter duration of peginterferon-ribavirin treatment was shown to be feasible in genotype 2/3 hepatitis C patients. Relapsers to previous standard interferon-based therapy had higher sustained virological response rates than previous non-responders when retreated with peginterferon-ribavirin. Hepatitis C patients with advanced liver disease may achieve sustained virological response with peginterferon-ribavirin treatment, but the complication rate was high. SUMMARY: New insights into the management of viral hepatitis have been gained over the past year. The problem of antiviral resistance in chronic hepatitis B is real and treatment options need to keep evolving. Advances have been made in hepatitis C treatment including patients with genotypes 2 or 3 infection and decompensated cirrhosis.

Antiviral Agents↗
PubMed2006

Hepatitis B virus genotypes, precore and core promoter variants among predominantly Asian patients with chronic HBV infection in a Canadian center.

BACKGROUND AND AIMS: The epidemiology of hepatitis B virus (HBV) infection in North America may be changing as a result of immigration from endemic countries. The purpose of this study was to determine the prevalence of HBV genotypes, precore (PC) and core promoter (CP) variants, and the proportion of patients meeting treatment criteria for HBV. METHODS: A cross-sectional study of consecutive HBV patients attending a Canadian tertiary liver center was conducted. HBV DNA was quantified by polymerase chain reaction assay. HBV genotypes and variants were determined using a line probe assay. RESULTS: Two hundred and seventy-two patients were enrolled; 200 were not receiving treatment at enrollment, of whom 116 were men and 84 women with a mean age 42+/-14 years. Among this group, 177 (88%) patients were Asian and 19 (10%) were Caucasian and 69 (35%) patients were hepatitis B e antigen (HBeAg) positive. Genotypes B and C were found in 42% and 50% untreated patients, respectively; while CP and PC were detected in 52% and 43% patients, respectively. Approximately 20% patients not receiving treatment (29% HBeAg positive, 14% HBeAg negative) met AASLD guidelines for antiviral therapy. If lower cutoff values for alanine aminotransferase and HBV DNA levels were used, 49% patients would qualify for treatment. CONCLUSIONS: The vast majority of patients at a Canadian tertiary referral center were Asian. Virological and clinical characteristics of these patients reflect their country of origin. Our findings highlight the need to monitor the changing patterns of HBV infection in countries with large immigrant populations.

Asian People↗
PubMed2005

Virologic response and resistance to adefovir in patients with chronic hepatitis B.

BACKGROUND: The incidence and risk factors for adefovir-resistant HBV have not been clearly defined. AIMS: To characterize the virologic response to adefovir, to determine the rate of adefovir resistance and to explore factors associated with initial virologic response (IVR) and adefovir resistance. METHODS: All hepatitis B patients who received adefovir for > or =6 months at our center were prospectively monitored for virologic response and adefovir resistance. RESULTS: Forty three patients were included; mean treatment duration was 18 months (range 6-45). Thirty four (79%) patients had prior lamivudine. IVR was observed in 44% patients and associated with higher pretreatment ALT (P = 0.05) and the absence of HBeAg (P = 0.02). Six (14%) patients were found to have adefovir-resistant mutations. The cumulative probability of genotypic resistance to adefovir at month 24 was 22%. Patients with adefovir resistance were more likely to have been switched from lamivudine to adefovir monotherapy (P = 0.01), to be older (P = 0.04), and to be infected with HBV genotype D (P = 0.02). CONCLUSIONS: Roughly 50% of patients failed to achieve IVR on adefovir. The cumulative probability of adefovir resistance at 2 years was 22%. Our data suggest that combination of lamivudine and adefovir may prevent emergence of adefovir resistance in patients with lamivudine-resistant HBV.

Adenine↗
PubMed2005

Adefovir-resistant hepatitis B can be associated with viral rebound and hepatic decompensation.

BACKGROUND/AIMS: The susceptibility of adefovir-resistant hepatitis B virus (HBV) mutants is only reduced by 3-10-fold in in vitro studies, suggesting that virologic breakthrough and clinical deterioration are unlikely. The aim of this study was to describe the clinical course of patients with adefovir-resistant HBV infection. METHODS: Testing for adefovir-resistant mutations was performed on patients who had a suboptimal response or virologic breakthrough on adefovir. Adefovir-resistant mutations were detected using a line probe assay and direct sequencing of the HBV P-gene. RESULTS: Eight male patients with pre-existing lamivudine resistance or breakthrough (mean age 47+/-13 years) were found to have adefovir-resistant mutations rtA181V/T or rtN236T. Baseline median ALT was 66 IU/L (range, 27-1161) and median HBV DNA 7.9 log10 copies/ml (range, 6-8.3). At the time of adefovir resistance (mean of 20+/-9 months), HBV DNA increased to > or = 5 log10 copies/ml in 7 patients. After detection of adefovir resistance, hepatic decompensation occurred in 2 patients, 1 of whom died. Salvage therapy with lamivudine, entecavir or tenofovir was given to 7 patients and a reduction in HBV DNA by > or = 3 log10 was seen in 3 patients. CONCLUSIONS: In conclusion, adefovir resistance can be associated with significant viral rebound and hepatic decompensation which may be fatal.

Adenine↗
PubMed2005

Predicting cirrhosis in patients with hepatitis C based on standard laboratory tests: results of the HALT-C cohort.

Knowledge of the presence of cirrhosis is important for the management of patients with chronic hepatitis C (CHC). Most models for predicting cirrhosis were derived from small numbers of patients and included subjective variables or laboratory tests that are not readily available. The aim of this study was to develop a predictive model of cirrhosis in patients with CHC based on standard laboratory tests. Data from 1,141 CHC patients including 429 with cirrhosis were analyzed. All biopsies were read by a panel of pathologists (blinded to clinical features), and fibrosis stage was determined by consensus. The cohort was divided into a training set (n = 783) and a validation set (n = 358). Variables that were significantly different between patients with and without cirrhosis in univariate analysis were entered into logistic regression models, and the performance of each model was compared. The area under the receiver-operating characteristic curve of the final model comprising platelet count, AST/ALT ratio, and INR in the training and validation sets was 0.78 and 0.81, respectively. A cutoff of less than 0.2 to exclude cirrhosis would misclassify only 7.8% of patients with cirrhosis, while a cutoff of greater than 0.5 to confirm cirrhosis would misclassify 14.8% of patients without cirrhosis. The model performed equally well in fragmented and nonfragmented biopsies and in biopsies of varying lengths. Use of this model might obviate the requirement for a liver biopsy in 50% of patients with CHC. In conclusion, a model based on standard laboratory test results can be used to predict histological cirrhosis with a high degree of accuracy in 50% of patients with CHC.

Adult↗
PubMed2005

Serum alpha-fetoprotein levels in patients with advanced hepatitis C: results from the HALT-C Trial.

BACKGROUND/AIMS: Alpha-fetoprotein (AFP) has been useful in the diagnosis of hepatocellular carcinoma (HCC) but lacks specificity. We assessed serum AFP among patients with chronic hepatitis C and advanced fibrosis to establish predictors of AFP elevations and changes with antiviral therapy. METHODS: Serum AFP was measured at baseline and on therapy in patients in the Hepatitis C Antiviral Long-Term Treatment against Cirrhosis (HALT-C). AFP levels were correlated with patient demographic and clinical features. RESULTS: Baseline AFP was > or = 20 ng/mL in 191 of 1145 patients (16.6%). Mean AFP values were significantly higher in patients with cirrhosis than in those with bridging fibrosis (22.5 vs. 11.4 ng/mL, P < 0.0001). Factors independently associated with raised serum AFP in patients with cirrhosis were female gender, black race, decreased platelet count, increased serum AST/ALT ratio, serum ferritin, and Mallory bodies in liver biopsies. Serum AFP levels decreased significantly during therapy with pegylated interferon alpha-2a and ribavirin. HCC was identified in six subjects, only three of whom had AFP > 20 ng/mL. CONCLUSIONS: Among patients with advanced chronic hepatitis C, serum AFP values are frequently elevated, even in the absence of HCC. Factors associated with raised AFP include severity of liver disease, female gender and black race. Serum AFP levels decline during antiviral therapy.

Alanine Transaminase↗