Increased spine bone density in patients with chronic hepatitis B switched to tenofovir alafenamide: A prospective, multinational study

BACKGROUND

Data on patients switched to tenofovir alafenamide (TAF) from nucleos(t)ide analogues (NUCs) other than tenofovir disoproxil fumarate are limited.

AIMS

To assess the treatment and renal/bone safety outcomes following the switch to TAF.

METHODS

We prospectively enrolled adult patients with chronic hepatitis B (CHB) who switched from any NUC to TAF at 14 centres in Japan, Korea, Taiwan and the U.S. Study outcomes were viral suppression (VR; HBV DNA < 20 IU/mL), biochemical response (BR; alanine aminotransferase normalisation), and changes in estimated glomerular filtration rate (eGFR) and T-scores (L-spine) by bone absorptiometry by 24 months after switch to TAF.

RESULTS

We enrolled 270 eligible patients. Mean age was 58.1; 58.2% were male; 12.2% had cirrhosis and 73.3% previously received entecavir monotherapy. VR rate increased significantly from 95.2% to 98.8% by 24 months after the switch to TAF (p = 0.014). Between the switch and 24 months later, the mean spine T-score improved significantly from -1.43 ± 1.36 to -1.17 ± 1.38 (p < 0.0001), while there was no significant change in mean eGFR (88.4 ± 16.9-89.5 ± 16.3 mL/min/1.73 m2 , p = 0.13). On multivariable analysis adjusted for age, sex, baseline spine T-score and prior TDF or adefovir dipivoxil use, male sex was significantly associated with lower risk of worsening spine T-score (odds ratio: 0.29, p = 0.020), while age was significantly associated with a higher risk of worsening chronic kidney disease stage (OR: 1.07, p = 0.019).

CONCLUSIONS

At 24 months after the switch to TAF, VR rates and spine bone density improved significantly while renal function remained stable.

Antiviral therapy substantially reduces HCC risk in patients with chronic hepatitis B infection in the indeterminate phase

BACKGROUND AND AIMS

HCC risk in chronic hepatitis B (CHB) is higher in the indeterminate phase compared with the inactive phase. However, it is unclear if antiviral therapy reduces HCC risk in this population. We aimed to evaluate the association between antiviral therapy and HCC risk in the indeterminate phase.

APPROACH AND RESULTS

We analyzed 855 adult (59% male), treatment-naïve patients with CHB infection without advanced fibrosis in the indeterminate phase at 14 centers (USA, Europe, and Asia). Inverse probability of treatment weighting (IPTW) was used to balance the treated (n = 405) and untreated (n = 450) groups. The primary outcome was HCC development. The mean age was 46±13 years, the median alanine transaminase was 38 (interquartile range, 24-52) U/L, the mean HBV DNA was 4.5±2.1 log 10 IU/mL, and 20% were HBeAg positive. The 2 groups were similar after IPTW. After IPTW (n = 819), the 5-, 10-, and 15-year cumulative HCC incidence was 3%, 4%, and 9% among treated patients (n = 394) versus 3%, 15%, and 19%, among untreated patients (n = 425), respectively ( p = 0.02), with consistent findings in subgroup analyses for age >35 years, males, HBeAg positive, HBV DNA>1000 IU/mL, and alanine transaminase

CONCLUSIONS

Antiviral therapy reduces HCC risk by 70% among patients with indeterminate-phase CHB. These data have important implications for the potential expansion of CHB treatment criteria.

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MESH Headings

• Adult
• Humans
• Male
• Middle Aged
• Female
• Carcinoma, Hepatocellular/epidemiology
• Carcinoma, Hepatocellular/etiology
• Carcinoma, Hepatocellular/prevention & control
• Hepatitis B, Chronic/complications
• Hepatitis B, Chronic/drug therapy
• Hepatitis B, Chronic/epidemiology
• Liver Neoplasms/epidemiology
• Liver Neoplasms/etiology
• Liver Neoplasms/prevention & control
• Alanine Transaminase
• DNA, Viral
• Hepatitis B e Antigens
• Antiviral Agents/therapeutic use
• Hepatitis B/complications
• Hepatitis B virus/genetics

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Real-world treatment outcome with protease inhibitor direct-acting antiviral in advanced hepatitis C cirrhosis: a REAL-C study

INTRODUCTION

Current guidelines discourage the use of direct-acting antiviral (DAA) containing protease-inhibitor (PI) in advanced HCV cirrhosis. We aimed to compare the real-world tolerability of PI vs. non-PI DAA regimens in this population.

METHODS

We identified advanced cirrhosis patients treated with DAA from the REAL-C registry. The primary outcome was significant worsening or improvement in CPT or MELD scores following DAA treatment.

RESULTS

From the REAL-C registry of 15,837 patients, we included 1077 advanced HCV cirrhosis patients from 27 sites. 42% received PI-based DAA. Compared to non-PI group, the PI group was older, had higher MELD and higher percentage with kidney disease. Inverse probability of treatment weighting (IPTW; matching on age, sex, history of clinical decompensation, MELD, platelet, albumin, Asia site, Asian ethnicity, hypertension, hemoglobin, genotype, liver cancer, ribavirin) was used to balance the two groups. In the IPTW-matched cohorts, the PI and non-PI groups had similar SVR12 (92.9% vs. 90.7%, p = 0.30), similar percentages of significant worsening in CTP or MELD scores at posttreatment week 12 and 24 (23.9% vs. 13.1%, p = 0.07 and 16.5% vs. 14.6%, p = 0.77), and similar frequency of new HCC, decompensating event, and death by posttreatment week 24. In multivariable analysis, PI-based DAA was not associated with significant worsening (adjusted odds ratio = 0.82, 95% CI 0.38-1.77).

CONCLUSION

Tolerability and treatment outcomes were not significantly different in advanced HCV cirrhosis treated with PI-based (vs. non-PI) DAA up to CTP-B or MELD score of 15. Safety of PI-based DAA in those with CTP-C or MELD beyond 15 awaits further data.

Liver Complications in Untreated Treatment-Ineligible versus Treated Treatment-Eligible Patients with Hepatitis B

BACKGROUND

A substantial number of patients who do not meet treatment criteria for chronic hepatitis B (CHB) later develop adverse outcomes such as cirrhosis and hepatocellular carcinoma (HCC). Our aim was to determine whether current practice guidelines adequately identify CHB patients who will benefit from antiviral therapy.

METHODS

We performed a retrospective cohort study comparing the incidence of adverse liver outcomes (cirrhosis and/or HCC) in untreated treatment-ineligible (at baseline and throughout follow-up) versus treated treatment-eligible patients according to standard American Association for the Study of Liver Diseases (AASLD) 2018 guidance (alanine aminotransferase [ALT] >70/50 U/L for men/women plus hepatitis B virus [HBV] DNA >20,000/2,000 IU/mL for HBeAg+/-) and with a sensitivity analyses using a lower threshold (ALT >40 U/L and HBV DNA >2,000 IU/mL).

RESULTS

We reviewed records of 5,840 patients from 5 clinics in California and identified 2,987 treatment-naive non-HCC CHB patients. Of those, 271 patients remained untreated treatment-ineligible, 514 patients were treatment-eligible and initiated treatment, with 5-year cumulative adverse liver incidences of 12.5% versus 7.2%, p = 0.074. On multivariable analysis adjusting for age, sex, diabetes, albumin, platelet count, and HBV DNA, compared to treated treatment-eligible patients, untreated treatment-ineligible patients had a significantly higher risk of adverse liver outcomes (adjusted hazard ratio: 2.38, 95% confidence interval 1.03-5.48, p = 0.04) in main analysis by AASLD 2018 criteria but not in sensitivity analysis using the lower treatment threshold (p = 0.09).

CONCLUSION

Patients never meeting standard AASLD 2018 criteria for antiviral therapy and never treated had twice the risk of developing cirrhosis and/or HCC when compared to eligible and treated patients.

Weight Loss and Weight Regain in Usual Clinical Practice: Results From the TARGET-NASH Observational Cohort

First-line treatment for nonalcoholic fatty liver disease (NAFLD) focuses on weight loss through lifestyle modifications.^1,2 Weight loss ≥5% results in reduction of steatosis and weight loss ≥10% has been associated with improvement in hepatic inflammation and fibrosis.³ The incidence and sustainability of weight loss among patients with NAFLD were estimated and associating factors identified.

Endoscopic evaluation during the COVID-19 pandemic: Observational study of the experience in community practices

Endoscopic screening is used widely to minimize the rates of colorectal cancer cases and deaths. During highly virulent infectious disease pandemics such as the coronavirus disease 2019 (COVID-19) pandemic, it is essential to weigh the risks and benefits of receiving endoscopy, especially in regions with moderately high viral infection rates. An observational study was conducted to assess the number of patients seen for endoscopic procedure at 2 of our surgery centers. Reasons for their procedure were collected in addition to information regarding any positive COVID-19 cases. This study considers the rate of severe acute respiratory syndrome coronavirus 2 infection along with the number of colorectal cancer cases encountered at a community endoscopy center to suggest that the benefits of undergoing endoscopic evaluation may outweigh the risks of attending an endoscopy procedure during the COVID-19 pandemic. One of the main reasons patients underwent endoscopic procedure was for colon cancer screenings (41.9%), and 5 of 1020 patients seen during the observation period were diagnosed with cancer. Of these 1020 patients, 8 were found to have positive tests for COVID-19 within 2 to 4 weeks after their procedure.

Treatment and Renal Outcomes Up to 96 Weeks After Tenofovir Alafenamide Switch From Tenofovir Disoproxil Fumarate in Routine Practice

BACKGROUND AND AIMS

Real-world data for treatment effectiveness and renal outcomes in chronic hepatitis B (CHB) patients who were switched to the new and safer prodrug tenofovir alafenamide (TAF) from tenofovir disoproxil fumarate (TDF) are limited. Therefore, we aimed to evaluate treatment and renal outcomes of this population.

APPROACH AND RESULTS

We analyzed 834 patients with CHB previously treated with TDF for ≥12 months who were switched to TAF in routine practice at 13 US and Asian centers for changes in viral (HBV DNA < 20 IU/mL), biochemical (alanine aminotransferase [ALT] < 35/25 U/L for male/female), and complete (viral+biochemical) responses, as well as estimated glomerular filtration rate (eGFR; milliliters per minute per 1.73 square meters) up to 96 weeks after switch. Viral suppression (P < 0.001) and ALT normalization (P = 0.003) rates increased significantly after switch, with a trend for increasing complete response (P_trend = 0.004), while the eGFR trend (P_trend  > 0.44) or mean eGFR (P > 0.83, adjusted for age, sex, baseline eGFR, and diabetes, hypertension, or cirrhosis by generalized linear modeling) remained stable. However, among those with baseline eGFR < 90 (chronic kidney disease [CKD] stage ≥2), mean eGFR decreased significantly while on TDF (P = 0.029) but not after TAF switch (P = 0.90). By week 96, 21% (55/267) of patients with CKD stage 2 at switch improved to stage 1 and 35% (30/85) of CKD stage 3-5 patients improved to stage 2 and 1.2% (1/85) to stage 1.

CONCLUSIONS

Overall, we observed continued improvement in virologic response, ALT normalization, and no significant changes in eGFR following switch to TAF from TDF.

Association Between Fatty Liver and Cirrhosis, Hepatocellular Carcinoma, and Hepatitis B Surface Antigen Seroclearance in Chronic Hepatitis B

BACKGROUND

Chronic hepatitis B (CHB) and fatty liver (FL) are common, natural history data on concurrent FL and CHB (FL-CHB) are limited. This study aimed to evaluate the effect of FL on cirrhosis, hepatocellular carcinoma (HCC), and hepatitis B surface antigen (HBsAg) seroclearance incidence in CHB patients.

METHODS

In a retrospective cohort study of 6786 adult CHB patients, we used propensity score matching (PSM) to balance the FL-CHB and non-FL CHB groups. Kaplan-Meier methods were used to compare cumulative cirrhosis, HCC, and HBsAg seroclearance rates between subgroups.

RESULTS

Before PSM, compared to non-FL CHB, FL-CHB patients had lower 10-year cumulative rates of cirrhosis, HCC, and a higher HBsAg seroclearance rate. Similar results were found in the matched FL-CHB and non-FL CHB patients, as well as in the antiviral-treated PSM cohort. Cox proportional hazards model indicated FL to remain significantly and strongly associated with lower risk of cirrhosis and HCC (hazard ratio [HR], 0.19 [95% confidence interval {CI}, .12-.33], P < .001 and HR, 0.21 [95% CI, .09-.51], P = .001, respectively) in antiviral-treated patients but not in untreated patients.

CONCLUSIONS

FL was significantly associated with lower cirrhosis and HCC risk and higher HBsAg seroclearance. Further studies are needed to confirm our funding and investigate the mechanisms underlying the impact of FL on CHB.

Development and Validation of a Risk Score for Liver Cirrhosis Prediction in Untreated and Treated Chronic Hepatitis B

BACKGROUND

Chronic hepatitis B (CHB) can progress to cirrhosis, but there are limited noninvasive tools available to estimate cirrhosis risk, including in patients receiving antiviral therapy. This study developed and validated a simple model to assess risk in CHB patients.

METHODS

The derivation cohort included 3000 CHB patients from 6 centers in the United States, with 52.60% receiving antiviral therapy. External validation was performed for 4552 CHB individuals from similar cohorts in Taiwan, with 21.27% receiving therapy. Cox proportional hazards regression analyses were used to screen predictors and develop the risk score for cirrhosis. Areas under receiver operating characteristic curves (AUROCs) were calculated for predictive value.

RESULTS

Sex, age, diabetes, antiviral treatment status/duration, hepatitis B e-antigen, and baseline alanine aminotransferase/aspartate aminotransferase levels were significantly associated with increased cirrhosis risk. A 13-point risk score was developed based on these predictors. The AUROCs for predicting cirrhosis risk were 0.82 at 3 years, 0.85 at 5 years, and 0.89 at 10 years in the derivation cohort, and 0.82, 0.79, and 0.77 in the validation cohort, respectively.

CONCLUSIONS

We developed and validated a simple cirrhosis prediction model with an independent external cohort that can be applied to both treatment-naive and treatment-experienced CHB patients in diverse settings and locations.

One-year Fibrosis-4 index helps identify minimal HCC risk in non-cirrhotic chronic hepatitis B patients with antiviral treatment

BACKGROUND AND AIMS

Fibrosis-4 (FIB-4) index is a HCC predictor in chronic hepatitis B (CHB) patients. However, little is known about whether FIB-4 helps identify non-cirrhotic CHB patients with minimal HCC risk after prolonged nucleos(t)ide analogue (NA) therapy.

METHODS

A total of 1936 ethnically diverse, non-cirrhotic CHB patients were enrolled in this retrospective multi-national study. All patients received prolonged NA treatment, including entecavir and tenofovir disoproxil fumarate. We explored whether FIB-4 cutoff of 1.30, a marker indicative of mild fibrosis severity, could stratify HCC risks in these patients.

RESULTS

A total of 48 patients developed HCC after a mean follow-up of 6.98 years. FIB-4 level at 1 year after treatment (1-year FIB-4) was shown to be associated with HCC development and was superior to pre-treatment FIB-4 value. When patients were stratified by 1-year FIB-4 of 1.30, the high FIB-4 group was at an increased HCC risk compared to the low FIB-4 group, with a hazard ratio of 4.87 (95% confidence interval: 2.48-9.55). Multivariable analysis showed that sex and 1-year FIB-4 were independent predictors, with none of the 314 female patients with low 1-year FIB-4 developing HCC. Finally, 1-year FIB-4 of 1.30 consistently stratified HCC risks in patients with low PAGE-B score, a score composed of baseline age, sex and platelet count, and the annual incidence rate of HCC was 0.11% in those with PAGE-B < 10 + 1-year FIB-4 < 1.30.

CONCLUSIONS

In non-cirrhotic CHB patients receiving prolonged NA therapy, 1-year FIB-4 < 1.30 is useful for identifying those with minimal HCC risk by combining with female sex or low PAGE-B score.

Real-World Effectiveness From the Asia Pacific Rim Liver Consortium for HBV Risk Score for the Prediction of Hepatocellular Carcinoma in Chronic Hepatitis B Patients Treated With Oral Antiviral Therapy

BACKGROUND

Patients on oral antiviral (OAV) therapy remain at hepatocellular carcinoma (HCC) risk. Risk prediction tools distinguishing treated patients with residual HCC risk are limited. The aim of this study was to develop an accurate, precise, simple-to-use HCC risk score using routine clinical variables among a treated Asian cohort.

METHODS

Adult Asian chronic hepatitis B (CHB) patients on OAV were recruited from 25 centers in the United States and the Asia-Pacific region. Excluded persons were coinfected with hepatitis C, D, or human immunodeficiency virus, had HCC before or within 1 year of study entry, or their follow-up was <1 year. Patients were randomized to derivation and validation cohorts on a 2:1 ratio. Statistically significant predictors from multivariate modeling formed the Real-world Effectiveness from the Asia Pacific Rim Liver Consortium for HBV (REAL-B) score.

RESULTS

A total of 8048 patients were randomized to the derivation (n = 5365) or validation group (n = 2683). The REAL-B model included 7 variables (male gender, age, alcohol use, diabetes, baseline cirrhosis, platelet count, and alpha fetoprotein), and scores were categorized as follows: 0-3 low risk, 4-7 moderate risk, and 8-13 high risk. Area under receiver operating characteristics were >0.80 for HCC risk at 3, 5, and 10 years, and these were significantly higher than other risk models (p < .001).

CONCLUSIONS

The REAL-B score provides 3 distinct risk categories for HCC development in Asian CHB patients on OAV guiding HCC surveillance strategy.

Incidence, Factors, and Patient-Level Data for Spontaneous HBsAg Seroclearance: A Cohort Study of 11,264 Patients

INTRODUCTION

Spontaneous hepatitis B surface antigen (HBsAg) seroclearance, the functional cure of hepatitis B infection, occurs rarely. Prior original studies are limited by insufficient sample size and/or follow-up, and recent meta-analyses are limited by inclusion of only study-level data and lack of adjustment for confounders to investigate HBsAg seroclearance rates in most relevant subgroups. Using a cohort with detailed individual patient data, we estimated spontaneous HBsAg seroclearance rates through patient and virologic characteristics.

METHODS

We analyzed 11,264 untreated patients with chronic hepatitis B with serial HBsAg data from 4 North American and 8 Asian Pacific centers, with 1,393 patients with HBsAg seroclearance (≥2 undetectable HBsAg ≥6 months apart) during 106,192 person-years. The annual seroclearance rate with detailed categorization by infection phase, further stratified by hepatitis B e antigen (HBeAg) status, sex, age, and quantitative HBsAg (qHBsAg), was performed.

RESULTS

The annual seroclearance rate was 1.31% (95% confidence interval: 1.25-1.38) and over 7% in immune inactive patients aged ≥55 years and with qHBsAg <100 IU/mL. The 5-, 10-, 15-, and 20-year cumulative rates were 4.74%, 10.72%, 18.80%, and 24.79%, respectively. On multivariable analysis, male (adjusted hazard ratio [aHR] = 1.66), older age (41-55 years: aHR = 1.16; >55 years: aHR = 1.21), negative HBeAg (aHR = 6.34), and genotype C (aHR = 1.82) predicted higher seroclearance rates, as did lower hepatitis B virus DNA and lower qHBsAg (P < 0.05 for all), and inactive carrier state.

DISCUSSION

The spontaneous annual HBsAg seroclearance rate was 1.31%, but varied from close to zero to about 5% among most chronic hepatitis B subgroups, with older, male, HBeAg-negative, and genotype C patients with lower alanine aminotransferase and hepatitis B virus DNA, and qHBsAg independently associated with higher rates (see Visual Abstract, Supplementary Digital Content 2, http://links.lww.com/CTG/A367).

Poor Adherence to Guidelines for Treatment of Chronic Hepatitis B Virus Infection at Primary Care and Referral Practices

BACKGROUND & AIMS

The American Association for the Study of Liver Diseases (AASLD) guidelines for treatment of chronic hepatitis B virus (HBV) infection have changed with time. We assessed rates of treatment evaluation and initiation in patients with chronic HBV infection from different practice settings in the past 14 years.

METHODS

Treatment-naive patients with chronic HBV infection were recruited from different practice settings in California from January 2002 through December 2016. The study population comprised 4130 consecutive, treatment-naive patients with chronic HBV infection seen by community primary care physicians (n = 616), community gastroenterologists (n = 2251), or university hepatologists (n = 1263). Treatment eligibility was assessed using data from the first 6 months after initial presentation based on AASLD criteria adjusted for changes over time.

RESULTS

Within the first 6 months of care, the proportions of patients evaluated by all 3 relevant tests (measurements of alanine aminotransferase, hepatitis B virus e antigen, and HBV DNA levels) were as follows: 36.69% in community primary care, 59.80% in gastroenterologist care, and 79.97% in hepatology care (P < .0001 among the 3 groups). Higher proportions of patients were eligible for treatment in specialty practices: 12.76% in community primary care, 24.96% in gastroenterologist care, and 29.43% in hepatology care (P < .0001). Among treatment-eligible patients, there was no significant difference in the proportions of patients who began antiviral therapy between those receiving treatment from a gastroenterologist (55.65%) vs a hepatologist (57.90%; P = .56). Of 243 evaluable patients receiving community primary care, only 31 were eligible for treatment and only 12 of these (38.71%) received treatment.

CONCLUSIONS

In an analysis of patients receiving care for chronic HBV infection, we found the proportions evaluated and receiving treatment to be suboptimal, according to AASLD criteria, in all practice settings. However, rates of evaluation and treatment were lowest for patients receiving community primary care.

Factors Associated With Rates of HBsAg Seroclearance in Adults With Chronic HBV Infection: A Systematic Review and Meta-analysis

BACKGROUND & AIMS

Seroclearance of hepatitis B surface antigen (HBsAg) is a marker for clearance of chronic hepatitis B virus (HBV) infection, but reported annual incidence rates of HBsAg seroclearance vary. We performed a systematic review and meta-analysis to provide more precise estimates of HBsAg seroclearance rates among subgroups and populations.

METHODS

We searched PubMed, Embase, and the Cochrane library for cohort studies that reported HBsAg seroclearance in adults with chronic HBV infection with more than 1 year of follow-up and at least 1 repeat test for HBsAg. Annual and 5-, 10-, and 15-year cumulative incidence rates were pooled using a random effects model.

RESULTS

We analyzed 34 published studies (with 42,588 patients, 303,754 person-years of follow-up, and 3194 HBsAg seroclearance events), including additional and updated aggregated data from 19 studies. The pooled annual rate of HBsAg seroclearance was 1.02% (95% CI, 0.79-1.27). Cumulative incidence rates were 4.03% at 5 years (95% CI, 2.49-5.93), 8.16% at 10 years (95% CI, 5.24-11.72), and 17.99% at 15 years (95% CI, 6.18-23.24). There were no significant differences between the sexes. A higher proportion of patients who tested negative for HBeAg at baseline had seroclearance (1.33%; 95% CI, 0.76-2.05) than those who tested positive for HBeAg (0.40%; 95% CI, 0.25-0.59) (P < .01). Having HBsAg seroclearance was also associated with a lower baseline HBV DNA level (6.61 log₁₀ IU/mL; 95% CI, 5.94-7.27) vs not having HBsAg seroclearance (7.71 log₁₀ IU/mL; 95% CI, 7.41-8.02) (P < .01) and with a lower level of HBsAg at baseline (2.74 log₁₀ IU/mL; 95% CI, 1.88-3.60) vs not having HBsAg seroclearance (3.90 log₁₀ IU/mL, 95% CI, 3.73-4.06) (P < .01). HBsAg seroclearance was not associated with HBV genotype or treatment history. Heterogeneity was substantial across the studies (I² = 97.49%).

CONCLUSION

In a systematic review and meta-analysis, we found a low rate of HBsAg seroclearance in untreated and treated patients (pooled annual rate, approximately 1%). Seroclearance occurred mainly in patients with less active disease. Patients with chronic HBV infection should therefore be counseled on the need for lifelong treatment, and curative therapies are needed.

Hepatitis B surface antigen loss and sustained viral suppression in Asian chronic hepatitis B patients: A community-based real-world study

Community-based real-world outcomes on effectiveness of antiviral therapies for chronic hepatitis B virus (CHB) in Asians are limited. Whether hepatitis B surface antigen (HBsAg) loss correlates with undetectable virus and alanine aminotransferase (ALT) normalization on treatment or what predicts risk of seroreversion or detectable virus after stopping therapy is unclear. We aim to evaluate rates and predictors of HBsAg loss, seroconversion, ALT normalization and undetectable HBV DNA, including HBsAg seroreversion or re-emergence of HBV DNA among Asian CHB patients. We retrospectively evaluated 1072 CHB adults on antiviral therapy at two community gastroenterology clinics from 1997 to 2015. Rates of HBsAg loss, ALT normalization, achieving undetectable HBV DNA and developing surface antibody (anti-HBs) were stratified by HBeAg status. Following HBsAg loss, HBsAg seroreversion or re-emergence of detectable HBV DNA was analysed. With median treatment of 76.7 months, the overall rate of HBsAg loss was 4.58%, with similar HBsAg loss rates between HBeAg-positive and HBeAg-negative patients (4.44% vs 4.71%, P=.85) in a predominantly Asian population (98.1%). Among HBsAg loss patients, 33.3% developed anti-HBs, 95.8% achieved undetectable virus and 66.0% normalized ALT. No significant baseline or on-treatment predictors of HBsAg loss were observed. While six patients who achieved HBsAg loss had seroreversion with re-emergence of HBsAg positivity, viral load remained undetectable, demonstrating the sustainability of viral suppression. Among a large community-based real-world cohort of Asian CHB patients treated with antiviral therapy, rate of HBsAg loss was 4.58%. Despite only 33.3% of HBsAg loss patients achieving anti-HBs, nearly all patients achieved sustained undetectable virus.

Partial Membership Latent Dirichlet Allocation for Soft Image Segmentation

Topic models [e.g., probabilistic latent semantic analysis, latent Dirichlet allocation (LDA), and supervised LDA] have been widely used for segmenting imagery. However, these models are confined to crisp segmentation, forcing a visual word (i.e., an image patch) to belong to one and only one topic. Yet, there are many images in which some regions cannot be assigned a crisp categorical label (e.g., transition regions between a foggy sky and the ground or between sand and water at a beach). In these cases, a visual word is best represented with partial memberships across multiple topics. To address this, we present a partial membership LDA (PM-LDA) model and an associated parameter estimation algorithm. This model can be useful for imagery, where a visual word may be a mixture of multiple topics. Experimental results on visual and sonar imagery show that PM-LDA can produce both crisp and soft semantic image segmentations; a capability previous topic modeling methods do not have.

Community-based real-world treatment outcomes of sofosbuvir/ledipasvir in Asians with chronic hepatitis C virus genotype 6 in the United States

Sofosbuvir/ledipasvir (SOF/LDV) is the first all-oral ribavirin-free treatment approved for chronic hepatitis C virus (HCV) genotype 6, offering a safe and highly efficacious treatment option. Large studies evaluating real-world outcomes of this regimen are lacking. We aim to evaluate real-world treatment outcomes for HCV genotype 6. A retrospective cohort study evaluated 65 adults (age ≥18) with chronic HCV genotype 6 treated with SOF/LDV without ribavirin at a community gastroenterology clinic in the United States from November 2014 to May 2016. Rates of undetectable virus at week 4 on treatment, at end of treatment (EOT) and SVR12 were stratified by the presence of cirrhosis and prior treatment (treatment naïve vs treatment experienced). Among 65 patients with chronic HCV genotype 6 treated with SOF/LDV (52.3% male, mean age 66.3 years [SD 9.7], 41.5% cirrhosis and 15.4% treatment experienced), 97.3% had undetectable virus at week 4 on treatment, 96.9% had undetectable virus at EOT and 95.3% achieved SVR12. SVR12 was 100% in females vs 91.2% in males, P=.096, and 92.3% in patients with cirrhosis vs 97.4% in those without cirrhosis, P=.347. Resistance testing of treatment failures was attempted but unsuccessful due to lack of conforming primers to define the possible resistance mutations. Among the largest U.S. community-based real-world cohort of Asian chronic HCV genotype 6 patients treated with all-oral SOF/LDV without ribavirin, SVR12 was similar to SVR12 reported in clinical trials, confirming the safety and effectiveness of this regimen and validating current HCV genotype 6 treatment guideline recommendations.

Randomized phase II study of GS-4774 as a therapeutic vaccine in virally suppressed patients with chronic hepatitis B

BACKGROUND & AIMS

GS-4774 is a heat-inactivated, yeast-based, T-cell vaccine designed to elicit hepatitis B virus (HBV)-specific T-cell responses. We evaluated the safety, tolerability and efficacy of GS-4774 in patients with chronic HBV infection.

METHODS

In this phase II study, 178 patients with chronic HBV infection and no cirrhosis who were virally suppressed on an oral antiviral (OAV) for ⩾1year were randomized (1:2:2:2) to continue OAV alone or receive OAV plus GS-4774 2, 10, or 40 yeast units (YU) subcutaneously every 4weeks until week 20. OAV was continued for the remainder of the study. Efficacy was measured by decline in serum hepatitis B surface antigen (HBsAg) from baseline to week 24.

RESULTS

Baseline characteristics were similar across groups (mean age, 45-50years; male, 62-74%; Asian, 68-80%; hepatitis B e antigen (HBeAg)-positive, 24-26%; mean HBsAg, 2.5-3.1log10IU/ml). There were no significant differences between groups in mean HBsAg declines from baseline to week 24 or 48. Five HBeAg-positive patients receiving GS-4774 experienced HBeAg loss vs. none in the control group. Three GS-4774 40 YU-treated patients had HBsAg declines ⩾0.5log10IU/ml, but no patient experienced loss of serum HBsAg. No virologic breakthrough occurred. Injection site reactions were the most frequent adverse event (AE), and there were no treatment discontinuations.

CONCLUSIONS

GS-4774 was well tolerated, but did not provide significant reductions in serum HBsAg in virally suppressed patients with chronic hepatitis B. Efficacy of GS-4774 in treatment-naïve patients remains to be determined.

LAY SUMMARY

GS-4774 is a therapeutic vaccine designed to improve the immune response against hepatitis B virus (HBV) in patients who already have chronic infection with HBV. In this study, GS-4774 was safe and well tolerated in patients with chronic HBV infection receiving oral antiviral therapy, but did not result in a clinical benefit. Combination approaches with other agents, and evaluation in other populations of patients with HBV are ongoing to determine if GS-4774 might have a therapeutic benefit.

CLINICAL TRIAL REGISTRATION NUMBER

NCT01943799.

Ethnic differences in incidence of hepatitis B surface antigen seroclearance in a real-life multicenter clinical cohort of 4737 patients with chronic hepatitis B infection

BACKGROUND

Hepatitis B surface antigen (HBsAg) positivity is associated with increased risk for cirrhosis and hepatocellular carcinoma (HCC). HBsAg seroclearance is thought to be rare in general, but cohort data from US patients are limited.

AIM

To determine the incidence of HBsAg seroclearance in a real-life US cohort.

METHODS

In total, 4737 patients with chronic hepatitis B from five primary care, gastroenterology and multispecialty centres, and a university medical centre were retrospectively enrolled between 2001 and 2014 with data obtained by manual review of individual patient medical records. Seroclearance was determined by loss of HBsAg seropositivity. Persistent HBsAg was confirmed by direct serology or by proxy with positive hepatitis B e-antigen (HBeAg) or HBV DNA levels.

RESULTS

HBsAg seroclearance occurred in 52 patients over 16 844 person-years (0.31% annually, 1.2% overall). Median follow-up was 32 months, and mean age 45 ± 14 years. Incidence of HBsAg seroclearance was higher in non-Asians, age >45, males, and those with baseline HBV DNA ≤10 000 IU/mL. On multivariate Cox proportional modelling, non-Asian ethnicity (HR 2.8), male sex (HR 2.1), baseline HBVDNA ≤10 000 (HR 2.0) and age >45 (HR 1.8) were significant independent predictors of seroclearance.

CONCLUSION

HBsAg seroclearance rates were lower than previously described in this real-life cohort of patients with chronic hepatitis B, especially among Asian, female and younger patients.

Lower liver cancer risk with antiviral therapy in chronic hepatitis B patients with normal to minimally elevated ALT and no cirrhosis

For chronic hepatitis B (CHB), alanine aminotransferase (ALT) ≥2 × upper limit of normal (ULN) is often used as a major criteria to initiate treatment in absence of cirrhosis, though patients with lower ALT may not be free from future risk of hepatocellular carcinoma (HCC). We aimed to examine the effect of antiviral therapy on HCC incidence based on ALT levels.We performed a retrospective study on 3665 patients consisting of United States and Taiwanese REVEAL-HBV cohort who were consecutive, treatment-naïve, noncirrhotic CHB patients aged ≥40 years. Patients were categorized by ALT cutoffs (≥2 × ULN vs <2 × ULN) and subgrouped by treatment status. Kaplan-Meier and Cox proportional hazards models were used to calculate cumulative incidence and hazard ratio (HR) of HCC adjusting for REACH-B scores.A total of 202 patients developed HCC. Antiviral treatment significantly reduced HCC risk: HR 0.24, 95% confidence interval 0.10-0.58; P = 0.001. HCC incidence per 100,000 person-years was significantly higher in untreated versus treated patients, even for those with ALT < 2 × ULN: 314.46 versus 0 per 100,000 person-years, P = 0.0042. For patients with Hepatitis B Virus (HBV) Deoxyribonucleic Acid (DNA) ≥ 2000 IU/mL, the number-needed-to-treat (NNT) were 15 and 14 to prevent 1 incident HCC at year 10 for patients with ALT < 2 × ULN and ≥2 × ULN, respectively.After adjustment by REACH-B score, antiviral treatment significantly decreased HCC incidence even in patients with ALT < 2 × ULN. NNT to prevent 1 incident HCC after 10 years of therapy was low (14-15) in patients with mildly elevated HBV DNA ≥ 2000 IU/mL regardless of ALT levels.

Renal Function in Chronic Hepatitis B Patients Treated With Tenofovir Disoproxil Fumarate or Entecavir Monotherapy: A Matched Case-Cohort Study

BACKGROUND AND AIMS

Tenofovir (TDF)-associated renal dysfunction has been described in various studies of human immunodeficiency virus-infected patients. Our goal is to examine the incidence and magnitude of decrease in renal function in chronic hepatitis B patients treated with TDF.

METHODS

We performed a case-cohort study of 103 patients on TDF 300 mg and 103 patients unexposed to TDF (Entecavir) at 4 centers, who were matched for age±10 years, sex, and baseline estimated glomerular filtration rate (eGFR) group. Calculation and evaluation of eGFR were performed with both the Cockcroft-Gault formula and the Modification of Diet in Renal Disease formula.

RESULTS

The exposed and unexposed populations were well matched with a similar mean age (44±10 y), proportion of male patients (63.1%), and baseline eGFR groups (86.4% unimpaired). There was no significant difference in the proportion of patients reclassified to a more severe renal classification (RMSRC) or in the proportion of patients with decrease in eGFR of ≥20% in those exposed to TDF versus control. The incidence density for RMSRC was 7.4 cases per 100 patient-years in the exposed group compared with 11.5 cases per 100 patient-years in the unexposed group (95% CI, 0.31-1.34). The relative risk of exposed to unexposed was 0.64 (95% CI, 0.31-1.34). On Cox proportional hazard analysis following adjustment for sex, age, baseline diagnosis hypertension, diabetes, impaired baseline renal function, and cirrhosis, TDF was not a predictor for RMSRC or decrease in eGFR≥20%.

CONCLUSIONS

TDF treatment was not an independent predictor for significant deterioration of renal function. Renal function of chronic hepatitis B patients on antiviral therapy should be monitored, especially in those who are older and/or with mildly impaired renal function.

Long-term follow-up and suboptimal treatment rates of treatment-eligible chronic hepatitis B patients in diverse practice settings: a gap in linkage to care

Background and aims

Despite available effective therapies, only a minority of patients with chronic hepatitis B (CHB) receive treatment. Our goal is to study treatment rates and time to treatment initiation in patients who meet treatment criteria on long-term follow-up.

Methods

We performed a retrospective cohort study of 608 consecutive treatment-eligible patients with CHB (by 2008 US Panel or 2009 American Association for the Study of Liver Disease (AASLD) criteria) at a US community gastroenterology clinic and a university liver clinic between 2007 and 2011. Patients were observed until they started treatment or last follow-up if untreated.

Results

Mean age was 44 and most were Asian (96%) with community patients being younger and having lower alanine aminotransferase (ALT) levels. A total of 62% started treatment, and 38% remained untreated after median follow-up of 17 months (IQR=1–40 months). Overall, treatment rate was significantly higher at university liver clinic than in the community (66.7% vs 59.9%, p=0.01). In multivariate analysis, older age (HR 1.02, p=0.002), male gender (HR 1.37, p=0.02), and baseline ALT >45 U/L for males and >29 U/L for females (HR 2.24, p<0.0001) were significant predictors of treatment initiation, but not practice setting.

Conclusions

Approximately 40% of treatment-eligible patients still have not started treatment on longer follow-up. Treatment rates were higher at university clinics, but practice setting was not a predictor for treatment, but older age, male gender, and higher ALT levels were. Further studies are needed to determine the barriers for treatment initiation and to improve treatment rates in treatment-eligible patients.

Safety and efficacy of entecavir in adefovir-experienced patients

BACKGROUND AND AIM

Suboptimal viral suppression with adefovir (ADV) poses a challenge in managing chronic hepatitis B. Few studies have evaluated the efficacy of entecavir (ETV) in ADV-experienced patients. Our aim is to assess treatment effectiveness of ETV in ADV-experienced patients.

METHODS

ADV-experienced patients switched to ETV were enrolled from six US clinics. Patients completed a median of 24 months of ETV after switch. Patients were categorized into partial responders (detectable HBV-DNA at switch) or complete responders (undetectable HBV-DNA at switch) to ADV. Primary and secondary outcome measurements were complete viral suppression (CVS, HBV-DNA < 60 IU/mL) and biochemical response (BR, alanine aminotransferase [ALT] < 40 U/L), respectively.

RESULTS

A total of 120 patients were included in the analysis (80 ADV partial responders; 40 ADV complete responders). In partial responders, CVS rate was 84% after 24 months of ETV. BR rate was 58% at switch to ETV and increased to 90% after 24 months. All complete responders continued to experience CVS after switch. On multivariate analysis inclusive of age, male gender, ALT level at switch, and history of lamivudine (LAM) exposure, we identified positive, hepatitis B e antigen status before ADV and higher HBV-DNA level at time of switch as significant independent negative predictors of CVS. In eight patients with ADV resistance, seven achieved CVS after 24 months of ETV, and all achieved BR.

CONCLUSION

In ADV-experienced patients, high rates of CVS and BR can be achieved/sustained after switching to ETV, including those with ADV resistance or with prior exposure to LAM.

Low treatment rates in patients meeting guideline criteria in diverse practice settings

BACKGROUND AND AIMS

Data on usage of antiviral therapy and application of chronic hepatitis B (CHB) management guidelines in different settings are limited. Our goal is to evaluate the proportion of treatment-eligible patients by 6-month follow-up and treatment rate among eligible patients by 12-month follow-up in diverse settings.

METHODS

In this retrospective cohort study, 1,976 treatment-naïve CHB patients were categorized as primary care physician (PCP) group if seen by community PCP (n = 329), gastroenterology (GI) group if seen by community gastroenterologists (n = 1,268), and hepatology group if seen by university hepatologists (n = 379). Treatment eligibility was based on the US Panel 2008 and American Association for the Study of Liver Diseases (AASLD) 2009 guidelines.

RESULTS

All groups had similar age, gender, and ethnic distribution. GI and hepatology groups had similar treatment eligibility rates by US Panel (53-54 %) and AASLD guidelines (24-25 %). However, treatment rate was significantly higher in hepatology compared to GI group by the US Panel guideline (59 vs. 45 %, P = 0.001). PCP group had the lowest eligibility and treatment rates by both guidelines. Common reasons for non-treatment were perceived "normal" alanine aminotransferase, desire for further observation, and patient refusal. Male gender, age >50, and subspecialty care predicted treatment initiation in treatment-eligible patients.

CONCLUSIONS

Less than half of treatment-eligible patients at primary care clinics received treatment. Community gastroenterology and university liver clinics treated about one-half to two-thirds of eligible patients. Patient and provider education should highlight treatment benefits and the new alanine aminotransferase upper limit of normal.

Mutations in HBV DNA polymerase associated with nucleos(t)ide resistance are rare in treatment-naive patients

BACKGROUND & AIMS

Prior studies have detected hepatitis B virus (HBV) DNA polymerase mutations in treatment-naive patients. However, most of these studies used either direct polymerase chain reaction sequencing, which detects these mutations with low levels of sensitivity, or patient cohorts that were not well-characterized. We investigated the prevalence of HBV mutations in DNA polymerase by using a line probe assay.

METHODS

In a prospective, cross-sectional study, we enrolled 198 treatment-naive patients with chronic hepatitis B (52.5% male; mean age, 41 years) from February 2009 to May 2011 from 3 gastroenterology and liver clinics in Northern California. Exclusion criteria included infection with hepatitis C or D viruses or human immunodeficiency virus. All patients completed a questionnaire (to determine demographics, history of liver disease, prior treatments, family medical history, drug and alcohol use, and environmental risk factors for hepatitis) that was administered by a research coordinator; mutations in HBV DNA polymerase were detected by using the INNO-LiPA HBV DR v.3 assay.

RESULTS

Most patients were Vietnamese (48.5%) or Chinese (36.4%) and were infected with HBV genotypes B (67.5%) or C (24.2%). Mutations in HBV DNA polymerase were found in 2 patients (1%), rtI233V (n = 1) and rtM250M/L (n = 1).

CONCLUSIONS

In a multicenter prospective study of treatment-naive patients with chronic hepatitis B, we detected mutations in HBV DNA polymerase in only 1%. Because of the low prevalence of these mutations and the uncertain clinical significance of such quasispecies, routine HBV DNA polymerase mutation analysis cannot be recommended before initiation of antiviral therapy for treatment-naive patients with chronic hepatitis B. The analysis requires further molecular and clinical studies.

Tenofovir is superior to entecavir for achieving complete viral suppression in HBeAg-positive chronic hepatitis B patients with high HBV DNA

BACKGROUND

Entecavir (ETV) and tenofovir disoproxil fumarate (TDF) are the two first-line anti-viral therapies for chronic hepatitis B (CHB); however, there are limited studies directly comparing their effectiveness.

AIM

To compare the effectiveness of ETV and TDF in nucleos(t)ide-naïve CHB patients with high hepatitis B virus (HBV) DNA levels, defined as serum HBV DNA greater than 6 log10  IU/mL.

METHODS

We performed a retrospective multicentre cohort study of adult CHB patients who were seen between 2009 and 2012 at four Northern California community gastroenterology and hepatology clinics.

RESULTS

We identified 59 consecutive patients treated with TDF and 216 patients treated with ETV. Pre-treatment characteristics were similar between the two groups. Among HBeAg-negative patients, there was no significant difference in viral suppression rates between ETV and TDF (P = 0.72). In contrast, among HBeAg-positive patients, those treated with TDF achieved viral suppression significantly more rapidly than those treated with ETV (P < 0.0001); the Kaplan-Meier estimated probability of complete suppression was 18% vs. 11% at 6 months, 51% vs. 28% at 12 months and 72% vs. 39% at 18 months respectively. Multivariate Cox proportional hazards analysis indicated that treatment with TDF compared to ETV was a significant predictor of viral suppression, but only for HBeAg-positive patients (HR = 2.59; 95% CI 1.58-4.22; P < 0.001).

CONCLUSION

Tenofovir is significantly more effective than entecavir for achieving complete viral suppression in HBeAg-positive, nucleos(t)ide-naïve chronic hepatitis B patients with HBV DNA greater than 6 log10  IU/mL.

Similar response to entecavir 0.5 and 1.0 mg in treatment-naïve chronic hepatitis B patients: a case-control study

BACKGROUND AND AIMS

The dose recommendation for entecavir (ETV) is 0.5 mg daily for treatment-naïve chronic hepatitis B (CHB) patients and 1.0 mg daily for lamivudine-refractory patients; however, few data are available for the efficacy of a 1.0-mg daily dose in treatment-naïve CHB patients. Our goal is to examine the treatment outcome of treatment-naïve patients placed on ETV 0.5 mg or ETV 1.0 mg daily through week 48.

METHODS

Cases were 40 consecutive hepatitis B e antigen (HBeAg)-positive CHB patients treated with ETV 1.0 mg daily between January 2005 and September 2010, and controls were 40 consecutive CHB patients treated with ETV 0.5 mg daily between January 2005 and September 2010 at three US gastroenterology/liver clinics. Controls were matched for age (±5 years), sex, HBeAg, and baseline hepatitis B virus (HBV) DNA (±0.5 log10 IU/ml). Complete viral suppression was defined as undetectable HBV DNA by polymerase chain reaction (<100 IU/ml).

RESULTS

Both groups had similar distributions of age (38 ± 11 years), male patients (55 %), and mean HBV DNA (7.7 ± 1.1 log10 IU/ml). The complete viral suppression rate was similar in both cases and controls through week 24 (15 vs. 15 %, p = 1.00) and week 48 (22 vs. 36 %, p = 0.17). Non-adherence was reported in three patients in the ETV 1.0 mg daily cohort at week 48.

CONCLUSIONS

There were no significant differences in the proportion of patients with complete viral suppression in patients treated with ETV 0.5 mg daily or the higher daily dose of 1.0 mg.

Less-established risk factors are common in Asian Americans with hepatitis C virus: a case-controlled study

BACKGROUND AND AIMS

The Centers for Disease Control and Prevention recommend screening for hepatitis C virus (HCV) in patients with injection drug use, blood transfusion before 1992, stigmata of liver disease, or born between 1945 and 1965. The purpose of this study was to examine risk factors for HCV acquisition in Asian Americans.

METHODS

This was a case-controlled study, with 471 consecutive patients testing positive for anti-HCV between January 2001 and December 2008. Controls included 471 patients with negative HCV matched at a one-to-one ratio for sex, age (±5 years), and ethnicity.

RESULTS

For Asian patients, the most common risk factors were blood transfusion and acupuncture or exposure to dirty needles (27 and 20 %, respectively). On multiple logistic regression, potential predictors for a positive anti-HCV test in Asians were acupuncture or exposure to dirty needles (OR = 12.9, P < 0.0001), body tattoo (OR = 12.0, P = 0.001), and history of blood transfusion (OR = 5.7, P < 0.0001).

DISCUSSION

Acupuncture and exposure to dirty needles are independent risk factors of HCV infection. Asians coming from endemic areas should be screened for HCV even when commonly-known risk factors for Western patients are not present.

Prevalence, risk factors, and disease knowledge of chronic hepatitis B infection in Vietnamese Americans in California

Our goal is to examine the prevalence, risk factors, and disease knowledge of chronic hepatitis B (CHB) among Vietnamese Americans in California. We also examined treatment eligibility and linkage to care among patients who tested positive for CHB. We enrolled 717 subjects from ten different hepatitis B virus (HBV) screening events in five locations from January 2009 to June 2010 in California. HBV status was determined by hepatitis B surface antigen (HBsAg) and antibody. Data were collected by a 36-question survey. A total of 99 patients (13.8 %) had positive HBsAg, especially those aged 31-40 years (23.6 %), and 177 (24.7 %) were still susceptible to HBV infection. A significant proportion of those who were HBsAg positive or still susceptible reported a history of HBV vaccination (10 and 20 %, respectively). Following adjustments for age and sex, significant predictors for HBsAg positivity were lack of healthcare coverage (OR=2.4, p=0.004), having a family history of CHB (OR=2.1, p=0.009), and prior occupational exposure (OR=3.0, p=0.007). Of those who tested positive, 13.3 % met criteria for antiviral therapy, but none had been initiated on treatment. HBV prevalence in Vietnamese Americans in California was high (13.8 %), especially in those between 31 and 40 years of age. Patient disease and treatment knowledge was poor, as were follow-up and management of those found to have CHB and/or have indication for antiviral therapy.

Treatment eligibility of patients with chronic hepatitis B initially ineligible for therapy

BACKGROUND & AIMS

Chronic hepatitis B (CHB) is a dynamic disease, therefore patients initially ineligible for treatment, based on current guidelines, often become eligible at some point during their follow-up evaluation. We investigated the reasons for this change and developed a timeline for treatment eligibility for this population.

METHODS

We performed a retrospective cohort study of 245 consecutive treatment-naive, community-based patients with CHB who were not eligible for treatment when they first presented, from March 2007 through June 2010 (mean age, 44 y, almost all Asian). The patients were followed up for a median period of 26 months, receiving standard laboratory tests. They were treated according to US panel 2008 and American Association for Liver Disease (AASLD) 2009 guidelines.

RESULTS

Fifty-four patients (22%) became eligible for treatment during the follow-up period; most of these (n = 47; 87%) were based on only the US Panel algorithm and the rest were based on AASLD guidelines (n = 7; 13%). Six percent of patients met the treatment criteria at 1 year, 18% at 2 years, and 29% at 3 years. Among hepatitis B e antigen-positive patients with levels of hepatitis B virus (HBV) DNA greater than 3 log IU/mL at baseline, 11% met treatment criteria at 1 year, 52% at 2 years, and 80% at 3 years. Based on Cox multivariate analysis, which included age; sex; and levels of hepatitis B e antigen, alanine aminotransferase, and HBV DNA, an increase in HBV DNA level was the only factor from the US panel associated with treatment eligibility (hazard ratio, 1.43; P < .001), and an increase in alanine aminotransferase was the only factor associated with treatment eligibility from the AASLD guidelines (hazard ratio, 1.03; P = .001).

CONCLUSIONS

Although most patients with CHB who initially are not eligible for treatment remain ineligible, almost 30% become eligible within 3 years. These findings indicate the importance of carefully following disease status in patients with CHB.

Low incidence of hepatitis B e antigen seroconversion in patients treated with oral nucleos(t)ides in routine practice

BACKGROUND AND AIM

Treatment end-point of therapy for patients with hepatitis B e antigen (HBeAg)-positive chronic hepatitis B (CHB) includes HBeAg seroconversion, which ranges from 15% to 22% after 1 year of oral nucleos(t)ides according to clinical trials. Our goal was to determine the incidence and predictors of HBeAg seroconversion in such patients in routine clinical practice because they may differ than reported rates.

METHODS

We conducted a retrospective cohort study of 333 consecutive treatment-naïve HBeAg-positive patients who were treated for CHB between 1/2000 and 6/2010 at three gastroenterology and liver clinics in the USA. Primary study end-point was HBeAg seroconversion-loss of HBeAg and antibody to HBeAg (anti-HBe) development.

RESULTS

The majority of patients were Asian (96%). Median treatment duration prior to HBeAg seroconversion was 50 (range 26-52) weeks. Of the 333 study patients, 25% received lamivudine, 16% adefovir, 51% entecavir, and 8% tenofovir. HBeAg seroconversion at month 12 was 8.2%. On multivariate analysis inclusive of age, gender, and antiviral agents, independent predictors for HBeAg seroconversion at month 12 were hepatitis B virus DNA < 7.5 log10  IU/mL (hazard ratio [HR] = 2.59 [1.04-6.44]), P = 0.041) and alanine transaminase (ALT) > 1.5 × upper normal limit (HR = 2.86 [1.05-7.81], P = 0.040), but not the choice of nucleos(t)ides.

CONCLUSIONS

The HBeAg seroconversion rate seen in clinical settings for oral nucleos(t)ides appears much lower than those reported in pivotal trials, especially in patients with lower ALT and higher HBV DNA levels. HBeAg-positive patients should be counseled about the high possibility of the long treatment duration required to achieve recommended treatment end-points.

Precore and basal core promoter mutations in Asian American patients with hepatitis B e antigen-positive chronic hepatitis B

BACKGROUND

Prior studies have shown that precore mutations abolish and basal core promoter (BCP) mutations down-regulate hepatitis B e antigen (HBeAg) production. Thus, the presence of precore and BCP mutations in HBeAg-positive patients indicates an infection with a mixed viral population of wild-type and precore and/or BCP mutant hepatitis B virus (HBV). To date, there has been limited study of the prevalence and clinical significance of precore and BCP mutations in patients with HBeAg-positive chronic hepatitis B.

AIM

To determine the prevalence, predictors and clinical characteristics of mixed wild-type and precore/BCP HBV infection, through a cross-sectional study, in a US cohort of patients with chronic hepatitis B.

METHODS

We conducted a retrospective study of 828 chronic hepatitis B patients with HBV genotype and mutation panel testing seen at three US gastroenterology and liver clinics from June 2005 to September 2009.

RESULTS

A majority of our patients (92.3%) were either Vietnamese or Chinese American. In the HBeAg-positive cohort, 17% of patients had precore mutations only, 28% had BCP mutations only and 5% had both BCP and precore mutations. On multivariate analyses, HBV genotype C, increasing age, lower HBV DNA level and an ALT quotient >2 were independent predictors for the presence of precore and/or BCP mutations.

CONCLUSIONS

The current distinction and management recommendations for HBeAg-positive vs. HBeAg-negative patients with chronic hepatitis B should be reassessed. Additional biomarkers and treatment endpoints should be studied for their usefulness in predicting continued viral suppression after treatment discontinuation.

Undertreatment of Asian chronic hepatitis B patients on the basis of standard guidelines: a community-based study

BACKGROUND AND OBJECTIVES

Previous studies have found that a major proportion of patients with chronic hepatitis B (CHB) do not receive antiviral therapy. The objective of this study was to characterize treatment eligibility on the basis of current guidelines, determine whether eligible patients actually receive treatment, and examine associated predictors.

METHODS

We conducted a retrospective study of patients who were evaluated for CHB at two community gastroenterology clinics between April 2007 and February 2009. Using criteria published by the American Association for the Study of Liver Diseases (AASLD) in 2007-2009 and by a panel of US hepatologists (US Panel) in 2006-2008, treatment eligibility was determined for the patients.

RESULTS

Of 612 consecutive CHB patients included, mean age was 44 ± 13 years, 54 % were male, and 99 % were Asian. Half (51 %) were eligible for treatment on the basis of the US Panel algorithm and 47 % of these patients also met AASLD treatment criteria. Overall, antiviral therapy was initiated for 50 % of eligible patients: 72 % of AASLD-eligible patients and 29 % of patients who were US Panel-eligible only. Independent predictors for actual treatment initiation were higher ALT for AASLD-eligible patients and higher ALT and older age for patients who were US Panel-eligible only. The leading reasons for nontreatment were further observation recommended by the physician, followed by loss of follow-up and patient refusal.

CONCLUSIONS

Approximately half of the CHB patients evaluated at community referral clinics met treatment criteria of at least one guideline; however, only about half received antiviral therapy within 12 months of presentation. Further studies are needed to optimize treatment of eligible CHB patients.

Liver disease in Viet Nam: screening, surveillance, management and education: a 5-year plan and call to action

Despite a high prevalence of liver disease in Viet Nam, there has been no nationwide approach to the disease and no systematic screening of at-risk individuals. Risk factors include chronic hepatitis B (estimated prevalence of 12%), chronic hepatitis C (at least 2% prevalence), and heavy consumption of alcohol among men. This combination of factors has resulted in liver cancer being the most common cause of cancer death in Viet Nam. There is a general lack of understanding by both the general public and health-care providers about the major risk to health that liver disease represents. We report here the initial steps taken as part of a comprehensive approach to liver disease that will ultimately include nationwide education for health-care providers, health educators, and the public; expansion of nationwide screening for hepatitis B and C followed by hepatitis B virus vaccination or treatment of chronic hepatitis B and/or hepatitis C; education about alcoholic liver disease; long-term surveillance for liver cancer; reduction of infection transmission related to medical, commercial, and personal re-use of contaminated needles, syringes, sharp instruments, razors, and inadequately sterilized medical equipment; and ongoing collection and analysis of data about the prevalence of all forms of liver disease and the results of the expanded screening, vaccination, and treatment programs. We report the beginning results of our pilot hepatitis B screening program. We believe that this comprehensive nationwide approach could substantially reduce the morbidity and mortality from liver disease and greatly lessen the burden in terms of both lives lost and health-care costs.

The efficacy of entecavir therapy in chronic hepatitis B patients with suboptimal response to adevofir

BACKGROUND

An increasing number of patients with chronic hepatitis B (CHB) have experienced treatment failure to adefovir (ADV) and their management poses a growing challenge. Very limited data are available on the efficacy of entecavir (ETV) in patients previously treated with ADV.

AIM

To examine the effect of ETV monotherapy on HBV DNA and ALT levels in CHB patients previously treated with ADV, but switched to ETV due to suboptimal response.

METHODS

Study candidates were enrolled from five community gastroenterology clinics in the U.S. Each completed at least 12 months of ETV treatment after being previously treated with ADV and experiencing suboptimal response. Primary and secondary outcome measurements were complete viral suppression (CVS, HBV DNA <100 IU/mL) and biochemical response (BR, ALT < 40 U/L), respectively.

RESULTS

A total of 60 patients were included in this analysis. Twelve were lamivudine (LAM)-experienced and none were LAM-resistant. At time of switch to ETV, no patients had experienced CVS. The CVS rate was 68% after 12 months of ETV therapy. The BR rate was 67% at switch to ETV and 80% after 12 months. There was no significant difference in response rates between LAM-experienced and naïve patients. Among the eight patients with ADV resistance, each achieved CVS after 12 months of ETV therapy and seven achieved BR.

CONCLUSIONS

In patients with suboptimal response to adefovir, complete viral suppression and biochemical response can be achieved in the majority by 12 months after switching to entecavir, including patients with prior exposure to lamivudine and those with adefovir resistance.

Medication nonadherence with long-term management of patients with hepatitis B e antigen-negative chronic hepatitis B

BACKGROUND AND AIMS

Antiviral treatment responses for patients with hepatitis B e antigen (HBeAg)-negative chronic hepatitis B (CHB) are well-defined by data from registration trials but may differ from patients seen in community settings where medical adherence is usually not as strictly monitored. The goal of this study was to examine the long-term outcomes of HBeAg-negative patients in a community clinical setting.

METHODS

We performed a cohort study of 189 consecutive treatment-naïve patients with CHB who were treated with either entecavir (ETV) 0.5 mg daily (n=107) or adefovir dipivoxil (ADV) 10 mg daily (n=82) from 2002 to 2009 at two community clinics.

RESULTS

All patients were Asians. Both ETV and ADV cohorts had similar median baseline ALT and HBV DNA levels. By year 4, a similar proportion of ETV and ADV patients who remained on monotherapy achieved complete viral suppression (91-96%); however, more patients in the ADV cohort required alternative therapy (27 vs. 5%). No patients in the ETV cohort developed resistance while 18% of the ADV cohort did. Cumulative nonadherence rates were 10 and 12% in ADV and ETV cohorts, respectively.

CONCLUSIONS

Failure to monotherapy in a community clinical setting is due to both antiviral resistance and patient nonadherence. Medication nonadherence is likely to be a more important contributor to treatment failure than antiviral resistance, especially with new anti-HBV agents such as ETV and tenofovir.

Ethnic differences in viral dominance patterns in patients with hepatitis B virus and hepatitis C virus dual infection

Studies of hepatitis B virus (HBV)/hepatitis C virus (HCV) dual infection are limited. Most are small, conducted outside the United States, and compare dual infection with HCV monoinfection. The goal of this study was to characterize HBV/HCV dual infection in a large multiethnic, matched, case-control study of dual-infected and HBV-monoinfected patients at two United States centers. Using an International Classification of Disease Version 9 electronic query and chart review, we identified 115 HBV/HCV dual-infected patients with serial HBV DNA, HCV RNA, and alanine aminotransferase (ALT) levels. As a control, 115 HBV-monoinfected patients were chosen randomly and matched with cases by age ±10 years, sex, Asian versus non-Asian ethnicity, and study site. Both groups had similar sex, ethnic, and age distributions (68% male, 83% Asian, age 52 ± 14 years). The median follow-up times were 33 and 38 months for the dual-infected and monoinfected groups, respectively. More monoinfected patients received HBV antiviral therapy than dual-infected patients (43% versus 24%; P = 0.002). No significant difference was detected between the proportion of monoinfected versus dual-infected patients with ALT above 40 U/L at presentation or during follow-up. Dual infection patients exhibited very little HBV/HCV codominance at baseline and throughout follow-up: patients had either HBV viremia with low or absent HCV RNA or detectable HCV RNA with low or absent HBV DNA. Asian ethnicity was predictive of HBV dominance after adjusting for sex, age, and baseline ALT elevation (odds ratio 7.35; P = 0.01).

CONCLUSION

HBV/HCV dual-infected and HBV-monoinfected patients had similar clinical characteristics. Asian ethnicity is a major independent predictor of HBV-dominant disease, and HCV dominance with undetectable HBV DNA is more common in non-Asian individuals. Larger studies are needed to further characterize the natural history of HBV/HCV dual infection in Asian and non-Asian individuals.

Randomized controlled trial of pegylated interferon-alfa 2a and ribavirin in treatment-naive chronic hepatitis C genotype 6

Hepatitis C virus (HCV) genotype is an important criteria in determining duration of therapy and predictor of sustained virologic response (SVR) to pegylated interferon (PEG IFN) and ribavirin (RBV) therapy. Optimal duration of therapy for patients with HCV genotype 6 is not known. We conducted a multicenter, open-label randomized controlled trial of patients with HCV genotype 6 at five gastroenterology clinics in the western U.S. Patients were stratified by viral load and histologic stage and assigned to receive PEG IFN-α2a 180 μg subcutaneously weekly and weight-based oral RBV 800 to 1,200 mg daily for 24 or 48 weeks. Primary outcome measurement was SVR rate by intention-to-treat analysis. From February 2005 to October 2007 a total of 60 patients (age 51 ± 10 years, 47% male, log HCVRNA 6.3 ± 1.1 IU/mL) were enrolled: 27 patients to 24 weeks and 33 patients to 48 weeks of therapy. In the 24-week and 48-week groups, 96% and 97% achieved early virologic response (P = 0.90); 89% versus 94% achieved end of therapy virologic response (P = 0.48). SVR was achieved in 70% versus 79% of patients assigned to 24 weeks versus 48 weeks (P = 0.45). Rapid virologic response (RVR) was a significant predictor of SVR in the 48-week group and trending towards significance in the 24-week group: 82% and 83% of those with RVR achieved SVR versus 33% and 29% for the 24-week and 48-week groups, respectively (P = 0.07 and P = 0.02).

CONCLUSION

There was no significant difference in SVR rates in patients with HCV genotype 6 treated with PEG IFN-α2a and RBV for 24 versus 48 weeks.

Prevalence of hepatitis B virus DNA polymerase mutations in treatment-naïve patients with chronic hepatitis B

BACKGROUND

One of the most important factors in treatment failure using nucleos(t)ide analogues in chronic hepatitis B is anti-viral resistance. Primary drug resistance refers to amino acid changes in the hepatitis B virus polymerase/reverse transcriptase (rt) that result in reduced susceptibility to anti-viral agents. Pre-existing drug resistance mutations may occur in untreated patients and may affect their treatment outcomes.

AIM

To determine the prevalence of hepatitis B DNA polymerase mutations in treatment-naïve patients.

METHODS

We used a direct PCR sequencing test to detect DNA polymerase mutations in 472 consecutive treatment-naïve patients at two community gastroenterology clinics in Northern California.

RESULTS

A majority of patients were Asians (>95%), had either genotype B or C (95%) and had no evidence of cirrhosis or liver cancer (94%). Mean age was 45 +/- 13 and mean hepatitis B virus DNA was 5.3 +/- 1.8 log(10) IU/mL. Most patients did not have any detectable mutations (82.4%). Some (16.7%) had mutations of unknown clinical significance (rtV207M/L/I) and only 4 patients had rtA181A/S, rtA194S or M250I.

CONCLUSIONS

No rtM204V/I or rtN236T mutations were observed in our study. Less than 1% of our patients had mutations that can be associated with primary resistance to existing anti-viral therapies for hepatitis B virus.

Renal dysfunction in chronic hepatitis B patients treated with adefovir dipivoxil

Renal dysfunction has been reported in patients treated with adefovir dipivoxil (ADV); however, its incidence and clinical importance may be underappreciated given the lack of long-term follow-up and data outside of a clinical trial setting. Our goal was to examine the severity and incidence of renal dysfunction in a real-life setting for patients treated with ADV and whose baseline estimated glomerular filtration rate (eGFR) was >50 mL/minute. We performed a cohort study of 290 chronic hepatitis B patients: 145 patients treated with 10 mg ADV and 145 patients unexposed to ADV at two community clinics, who were matched for age (+/-10 years), sex, and baseline eGFR. The exposed and unexposed populations were well-matched with a similar mean age (46-47 years), proportion of male patients (76.5%), baseline serum creatinine (0.97-0.99 mg/dL), and baseline creatinine clearance (85.0-85.4 mL/minute). The incidence density for renal dysfunction defined by treatment termination and/or development of eGFR < or =50 mL/minute was five cases per 100 patient-years in the exposed group compared with 1.36 cases per 100 patient-years in the unexposed group (P = 0.02). The relative risk of exposed to unexposed was 3.68 (95% confidence interval 1.1-19.3). On Cox proportional hazard analysis also inclusive of sex, ADV was a significant predictor of significant renal dysfunction (hazard ratio [HR] 3.94, P = 0.03). There were also significant trends for age >50 years (HR 3.49, P = 0.087), mild renal impairment at baseline (HR 4.49, P = 0.073), and hypertension and/or diabetes mellitus (HR 2.36, P = 0.074).

CONCLUSION

ADV is an independent predictor for significant deterioration of renal function. Patients on ADV should be monitored, especially patients who are older, have baseline renal insufficiency, or have hypertension and/or diabetes mellitus.

Histological disease in Asian-Americans with chronic hepatitis B, high hepatitis B virus DNA, and normal alanine aminotransferase levels

OBJECTIVES

At present there is no clear consensus on how patients with chronic hepatitis B (CHB), high serum hepatitis B virus (HBV) DNA, and normal alanine aminotransferase (NLALT) levels should be managed. This study hypothesizes that a significant proportion of such patients may have histological disease.

METHODS

We carried out a retrospective study of 101 consecutive treatment-naive patients with CHB who underwent liver biopsies at a community gastroenterology clinic and had high HBV DNA and NLALT (< or = 40 U/l) levels at the time of biopsy. All patients were Asians. ALT levels were observed for a period of time before liver biopsy and were used to classify patients into two groups, namely those with only NLALT levels and those with fluctuating ALT (FLALT) levels. All patients had at least two ALT measurements during this period of time. Significant histology was defined as stage > or = 2 fibrosis or stage 1 fibrosis plus grade > or = 2 inflammation using the Batts-Ludwig scoring system.

RESULTS

In patients with NLALT levels, the proportions of those with significant histology were 0, 22, and 45% for age < or = 35, 36-50, and >50 years, respectively (n=11, n=27, n=19; P=0.033). In patients who had FLALT levels, the corresponding proportions were 22, 42, and 69% (n=9, n=22, n=13; P=0.091). After adjustments for gender, hepatitis B e antigen (HBeAg) status, and mean pre-biopsy HBV DNA levels, significant predictors of histological disease were older age (odds ratio (OR)=6.2 for age 36-50 years and OR=17.6 for age >50 years compared with age < or = 35 years, P=0.041 and P=0.003, respectively) and FLALT levels (OR=3.6, P=0.008). Sub-analysis of patients with NLALT levels using lower cutoffs (30 U/l for men and 19 U/l for women) showed similar trends.

CONCLUSIONS

Patients with CHB, high HBV DNA, and NLALT levels and aged more than 35 years or those with FLALT levels may have significant histological disease (22-70%).

Prevalence of hepatitis B virus genotype B in Vietnamese patients with chronic hepatitis B

PURPOSE

Hepatitis B virus (HBV) genotypes can affect treatment response to interferon-based therapy and disease outcomes in patients with chronic hepatitis B (CHB). Little data exist to characterize HBV genotypes in Vietnamese, one of the largest minority groups in the United States and also one with one of the highest CHB and liver cancer disease burdens. The goal of this study was to compare the distribution of HBV genotypes in Vietnamese and Chinese patients.

METHODS

We performed a cross-sectional study of 567 consecutive patients of Vietnamese (n = 478) or Chinese (n = 89) descent, with HBV genotype mutation analysis performed between 7/2,005 and 6/2,008 at a community gastroenterology clinic and a university-affiliated liver clinic in the United States.

RESULTS

There were no significant differences between the Vietnamese and Chinese groups in mean age (45 and 44 years), gender (58% and 61% male), HBeAg status (64% and 65% negative), median alanine aminotransferase (33 and 41 U/L), and log(10) HBV DNA (4.9 and 5.0 log(10) IU/ml), or the prevalence of precore/basic core promoter mutations (72% and 71%), respectively. Vietnamese patients had a much higher prevalence of HBV genotype B and a lower prevalence of genotype C than Chinese patients: 74% and 25% vs. 55% and 43% (P = 0.001).

CONCLUSIONS

Chinese patients with CHB often carry either B or C genotype. Vietnamese patients with CHB mostly have HBV genotype B. Additional studies are needed to further characterize the clinical significance of HBV genotype in the natural history and treatment outcomes of CHB in Vietnamese patients.

Higher rate of sustained virologic response in chronic hepatitis C genotype 6 treated with 48 weeks versus 24 weeks of peginterferon plus ribavirin

OBJECTIVES

Infection with hepatitis C virus (HCV) genotype 6 is common in patients from parts of China and Southeast Asia. No study to date has examined the treatment response to peginterferon and ribavirin (PEG IFN + RBV) in these patients, or the effects of treatment duration on sustained virologic response (SVR) rates.

METHODS

We performed a retrospective study of 190 consecutive Asian-American patients who were diagnosed with HCV genotype 6 at a gastroenterology clinic in northern California between 2001 and 2004, 66 of whom were treatment-naïve and subsequently completed 24 wk of IFN + RBV or PEG IFN + RBV or 48 wk of PEG IFN + RBV therapy. The primary outcome was SVR.

RESULTS

There was no statistical difference in SVR of 31 patients treated with 24 wk of IFN + RBV and in 23 patients treated with 24 wk of PEG IFN + RBV (51.6%vs 39%, P= 0.363). The SVR in 12 patients treated with 48 wk of PEG IFN + RBV was significantly higher than that in those treated for only 24 wk (75%vs 39%, P= 0.044).

CONCLUSIONS

Treatment-eligible patients with HCV genotype 6 should be treated with a full course of 48 wk as tolerated. Larger prospective studies of patients with HCV genotype 6 are needed to confirm the optimal treatment duration with PEG IFN + RBV.

Unsedated ultrathin EGD is well accepted when compared with conventional sedated EGD: a multicenter randomized trial

BACKGROUND & AIMS

In the United States, upper gastrointestinal endoscopy is usually performed using intravenous sedation. Sedation increases the rate of both complications and costs of endoscopy. Unsedated esophagogastroduodenoscopy (EGD) using conventional 8-11-mm endoscopes is an alternative to sedated endoscopy but is generally perceived as unacceptable to many American patients. Unsedated EGD using ultrathin 5-6-mm endoscopes is better tolerated. A randomized trial comparing unsedated ultrathin EGD (UT-EGD) with sedated conventional EGD (C-EGD) in a diverse American population is needed.

METHODS

In this multicenter, randomized, controlled trial, 80 patients scheduled to undergo elective outpatient EGD were randomized to unsedated UT-EGD or sedated C-EGD. The study was carried out at San Francisco General Hospital, San Francisco Veterans Affairs Medical Center, and the Liver and Digestive Health Medical Clinic, San Jose.

RESULTS

Baseline characteristics of patients randomized to unsedated UT-EGD and sedated C-EGD were similar. Moreover, there were no significant differences in overall patient satisfaction and willingness to repeat endoscopy in the same manner among the 2 study groups. There was, however, a significant difference in median total procedure time between the 2 study groups of 1.5 hours (P < 0.0001). The mean (+/- SD) total procedure cost was 512.4 US dollars (+/- 100.8 US dollars) for sedated C-EGD and 328.6 US dollars (+/- 70.3 US dollars) for unsedated UT-EGD (P < 0.0001).

CONCLUSIONS

Patients undergoing unsedated UT-EGD are as satisfied as patients undergoing sedated C-EGD and are just as willing to repeat an unsedated UT-EGD. Unsedated UT-EGD was also faster, less costly, and may allow greater accessibility to this procedure.

Heterogeneity of NH+4 transport in mouse inner medullary collecting duct cells

Previous studies from our laboratory have demonstrated that NH+4 substitutes for K+ on the Na(+)-K(+)-adenosinetriphosphatase (Na(+)-K(+)-ATPase) in rat terminal inner medullary collecting duct cells (tIMCD). To examine other NH+4 transport pathways, a transgenic mouse cell line, mIMCD-3, was employed. 86Rb+ was used as a K+ congener to explore NH+4/Rb+ (K+) competition on the extracellular K+ binding site of the Na(+)-K(+)-2Cl- cotransporter and the Na(+)-K(+)-ATPase. Addition of K+ or NH+4 reduced both bumetanide- and ouabain-sensitive Rb+ uptake. This reduction in Rb+ uptake with NH+4 addition was not due to intracellular pH-mediated changes in transporter activity. K+ and NH+4 are competitive inhibitors on both transporters. On the Na(+)-K(+)-2Cl- cotransporter, the Michaelis constant (Km) for K+ was 4.6 +/- 0.5 mM with an inhibitory constant (Ki) for NH+4 of 2.8 mM. In contrast, on the Na(+)-K(+)-ATPase, the apparent affinity for K+ was greater than for NH+4. To test Na(+)-K(+)-2Cl- cotransport-mediated NH+4 flux, bumetanide-sensitive NH+4/Rb+ exchange was measured. Bumetanide-sensitive Rb+ efflux was greater with extracellular K+ or NH+4 present relative to efflux with extracellular N-methyl-D-glucamine. This demonstrates both K+/Rb+ and NH+4/Rb+ countertransport by the Na(+)-K(+)-2Cl- cotransporter. In conclusion, NH+4 is transported in a bumetanide-sensitive Na(+)-NH+4-Cl- mode, and both NH+4 and Rb+ (K+) are competitive inhibitors for the extracellular K+ binding site. However, the kinetics of Na(+)-K(+)-2Cl(-)-mediated NH+4 transport differ from other K+ transport-mediated NH+4 pathways, such as the Na(+)-K(+)-ATPase.