Combination treatment of pegylated interferon and tenofovir versus tenofovir for people with chronic hepatitis B

Objectives

This is a protocol for a Cochrane Review (intervention). The objectives are as follows:

To evaluate the benefits and harms of pegylated interferon combined with tenofovir versus tenofovir monotherapy in adults with chronic hepatitis B.

Background

Description of the condition

Hepatitis B virus (HBV) is a small DNA virus, with ten known genotypes (designated A through J), and numerous subtypes (Lin 2011). HBV enters the cells of the main parenchymal tissue of the liver (i.e. hepatocytes (Block 2021; Kramvis 2022; Yan 2012)). Hepatocytes make up to 80% of the liver mass (Godoy 2013). The presence of hepatitis B surface antigen (HBsAg) in human blood serum indicates acute or chronic liver infection. HBV infection is considered chronic if HBsAg persists beyond six months (Terrault 2018).

According to the World Health Organization (WHO), around 1.5 million individuals were newly infected with chronic HBV, and 0.82 million people died of HBV infection in 2020 (WHO 2021). WHO set a goal of HBV elimination by 2030 (Revill 2019). Once people are infected with HBV, both anti‐HBV‐specific humoral and cellular immunity are activated, which results in hepatocyte damage and inflammation, and sometimes necrosis (Tang 2018). Persistent inflammation and necrosis increase the risk of developing liver cirrhosis and hepatocellular carcinoma (HCC (Cao 2022)). Almost 40% of people with HCC have a history of chronic HBV infection (Stanaway 2016). High HBV DNA level is a predictor for liver cirrhosis and HCC (Chen 2006; Iloeje 2006).

The European Association for the Study of the Liver (EASL), American Association for the Study of Liver Diseases (AASLD), and Chinese Medical Association practice guidelines suggest that chronic HBV infection should be classified into four major phases: hepatitis Be antigen (HBeAg)‐positive chronic HBV infection, HBeAg‐positive chronic hepatitis B, HBeAg‐negative chronic HBV infection, and HBeAg‐negative chronic hepatitis B, according to the viral replication and host immune response. In the HBeAg‐positive chronic HBV infection phase (the immune tolerant phase), HBV DNA levels are often very high, alanine aminotransferase (ALT) levels are normal, and there is minimal or no liver inflammation or fibrosis. In this phase, people are highly contagious because they have high levels of HBV DNA. In the HBeAg‐positive chronic hepatitis B phase (the immune active phase), HBV DNA and ALT levels are elevated, and there is liver inflammation and fibrosis. In this phase, people can achieve both HBeAg seroconversion and HBV DNA suppression. In the HBeAg‐negative chronic HBV infection phase (the inactive phase), ALT levels are normal, HBsAg and HBV DNA levels are low, and there is minimal liver inflammation and fibrosis; the rate of spontaneous HBsAg loss is 1% to 3% per year. In the HBeAg‐negative chronic hepatitis B phase (the immune reactivation phase), ALT and HBV DNA levels are elevated, and there is liver inflammation and fibrosis (Chinese Medical Association 2019; EASL 2017; Terrault 2018).

For people with HBeAg‐positive or ‐negative chronic hepatitis B, clinicians should consider the levels of ALT and HBV DNA, and the severity of the liver disease when deciding to initiate antiviral therapy (Chinese Medical Association 2019; EASL 2017). Anti‐HBV treatment is recommended in people with high HBV DNA levels and liver inflammation (Fanning 2019). Regardless of the degree of fibrosis, antiviral treatment should be started in people with HBV DNA levels of more than 20,000 IU/mL and ALT levels of more than twice the upper limit of normal (EASL 2017). Antiviral treatment should be started immediately in people with compensated cirrhosis, and a detectable level of serum HBV DNA (Chinese Medical Association 2019).

The goal of chronic hepatitis B treatment is to improve a person's survival, without the risk of virological relapse or progression of the liver disease after discontinuing antiviral treatment (EASL 2017). The 'cure' for chronic hepatitis B has been categorised into complete sterilising cure, functional cure, and partial cure. Complete sterilising cure is defined as the eradication of HBV DNA, including covalently closed circular DNA (cccDNA), and negative serum HBsAg (Tang 2018). However, currently available treatment options cannot completely eliminate cccDNA from hepatocytes. Therefore, it is difficult to achieve a complete sterilising cure. The most updated practice guidelines recommend functional cure, which they define as undetectable levels of serum HBsAg and HBV DNA, and the ideal goal of chronic hepatitis B treatment (Chinese Medical Association 2019; EASL 2017; Terrault 2018). HBsAg clearance is significantly associated with a reduced risk of cirrhosis and HCC (Anderson 2021; Lee 2013). The rate of viral relapse after the discontinuation of nucleos(t)ide analogue treatment is high, so it is often recommended that antiviral treatment be continued in people with HBeAg‐negative chronic hepatitis B until HBsAg loss is achieved (Kim 2014; Seto 2015).

Description of the intervention

Tenofovir is one of the mainstay drugs for chronic HBV infection (Lok 2017; Seto 2018). Both tenofovir disoproxil fumarate and tenofovir alafenamide are prodrugs of tenofovir. The US Food and Drug Administration (FDA) approved tenofovir disoproxil fumarate in 2008, and tenofovir alafenamide in 2016 for the treatment of HBV infection. The daily dose of tenofovir disoproxil fumarate is 300 mg; tenofovir alafenamide is 25 mg. Tenofovir carries a risk of drug resistance and causes adverse events (Abdul 2017).

Pegylated interferon is another first‐line treatment choice for chronic HBV infection (Seto 2018). Pegylated interferon was approved for the treatment of HBV infection in 2002 (Abdul 2017). The pegylated interferon dose is 180 μg, by subcutaneous injection, once a week. However, administration by injection may be inconvenient, and can frequently cause adverse events (WHO 2015). Contraindications include decompensated liver cirrhosis, severe psychiatric disorders, epilepsy, autoimmune disease, severe cardiac disease, and pregnancy (Terrault 2018). However, pegylated interferon results in higher rates of HBeAg and HBsAg loss than tenofovir (WHO 2015). A Chinese cost‐effectiveness analysis found that the cost per person to achieve HBsAg seroclearance was USD 42,315 for tenofovir disoproxil fumarate, USD 57,566 for tenofovir alafenamide, and USD 42,335 for pegylated interferon (Dai 2022). For those who are HBeAg‐positive, pegylated interferon is more cost‐effective than tenofovir to achieve HBeAg and HBsAg loss (Dai 2022).

Current combination regimens for pegylated interferon plus tenofovir include: de novo combination, pegylated interferon with add‐on tenofovir, and tenofovir with add‐on pegylated interferon (Ning 2019). A de novo combination regimen refers to the simultaneous initiation of pegylated interferon and tenofovir; add‐on combination regimen is defined as a prescription of pegylated interferon after the initiation of tenofovir, or that of tenofovir after the initiation of pegylated interferon.

How the intervention might work

Tenofovir suppresses the HBV replication pathway by inhibiting reverse transcription, and terminating DNA chain elongation (Liang 2015). Tenofovir monotherapy can have high rates of HBV DNA suppression and ALT normalisation, but its ability to achieve functional cure is still unsatisfactory (Buti 2020). In 48‐week tenofovir disoproxil fumarate monotherapy trials, the rate of HBsAg loss was 0% to 3% (Abdul 2017; Hu 2021; Lampertico 2020; Marcellin 2008; Yang 2021). By comparison, tenofovir combined with pegylated interferon inhibits the transcription of cccDNA and improves the initial response (Wursthorn 2006), probably because pegylated interferon has both antiviral and immunomodulatory effects, which affect both HBV replication and transcription (Revill 2019). It has been demonstrated that a combination of tenofovir disoproxil fumarate and pegylated interferon for 48 weeks can improve the virological response in people with chronic hepatitis B more than tenofovir disoproxil fumarate alone (Bahardoust 2020; Hu 2021; Liu 2020; Marcellin 2016; Qiu 2018; Zheng 2019). Because tenofovir and pegylated interferon affect immune response differently, their combination should improve the functional cure of chronic hepatitis B (Liang 2015).

Why it is important to do this review

The most current practice guidelines recommend entecavir, tenofovir disoproxil fumarate, tenofovir alafenamide, and pegylated interferon as the preferred choices of approved antiviral therapies for chronic hepatitis B, but there is no consensus about the use of combination regimens of tenofovir and pegylated interferon for chronic hepatitis B (Chinese Medical Association 2019; EASL 2017; Terrault 2018). To the best of our knowledge, there are two published meta‐analyses on this topic, but they have some limitations (Liu 2020; Qiu 2018).

• One meta‐analysis, published in 2018, included 24 studies, but reported the pooled rate of HBsAg clearance, rather than statistically comparing the clearance rate of combination therapy and monotherapy (Qiu 2018).

• A second meta‐analysis, published in 2020, included 49 studies and analysed both pegylated interferon and interferon‐α, which increased the heterogeneity of the treatment effect; different combination regimens were not statistically compared (Liu 2020).

• Both meta‐analyses evaluated heterogeneous nucleos(t)ide analogues, including lamivudine, telbivudine, adefovir, entecavir, and tenofovir disoproxil fumarate (Liu 2020; Qiu 2018). However, most updated practice guidelines do not recommend lamivudine, telbivudine, or adefovir, which have low barriers to resistance, as the preferred nucleos(t)ide analogues for chronic hepatitis B (Chinese Medical Association 2019; EASL 2017; Terrault 2018).

• Both meta‐analyses included observational studies, which potentially increase the risk of bias.

• Neither meta‐analysis analysed adverse events.

New evidence is available from recently published randomised clinical trials regarding combination treatment of pegylated interferon and tenofovir (Ahn 2018; Al Ashgar 2017; Bahardoust 2020; Broquetas 2020; Chi 2017; Lian 2022). Therefore, a Cochrane Review with meta‐analysis of only randomised clinical trials is needed to evaluate the benefits and harms of combination strategies versus tenofovir monotherapy.

Objectives

To evaluate the benefits and harms of pegylated interferon combined with tenofovir versus tenofovir monotherapy in adults with chronic hepatitis B.

Methods

Criteria for considering studies for this review

Types of studies

We will only include randomised clinical trials, with any trial design, that assess pegylated interferon combined with tenofovir versus tenofovir alone, in adults with chronic hepatitis B virus (HBV) infection. We will include trials regardless of whether they report the outcomes specified in our review. We will include trials regardless of the format, date, or language of publication. We will include data from sources of unpublished trials, if found.

We will exclude quasi‐randomised studies, as the method of their allocation is not truly random, and observational studies (e.g. case reports, case series, cross‐sectional studies, case‐control studies, and cohort studies).

Types of participants

We will include adults (at least 18 years old) with chronic HBV infection, regardless of the HBV genotype and subtype, HBeAg status (positive or negative), or history of treatment (treatment‐naïve or previous treatment).

Chronic HBV infection is characterised by the persistence of HBsAg in serum for at least six months. HBeAg‐positive is characterised by the persistence of HBeAg in serum. HBeAg‐negative is defined as loss of HBeAg with or without anti‐HBe antibodies in serum.

We will exclude participants with hepatitis C virus, hepatitis D virus, or HIV co‐infections; pregnant women; and participants with decompensated liver cirrhosis, chronic kidney disease, or transplanted organs.

Types of interventions

Experimental intervention

• pegylated interferon combined with tenofovir (tenofovir disoproxil fumarate or tenofovir alafenamide), regardless of dose, regimen, or route of administration; tenofovir should have been administered for at least 24 weeks

Control intervention

• tenofovir monotherapy

We will allow co‐interventions if administered in the same way to the participants in all trial groups, fulfilling the inclusion criteria of our review.

Types of outcome measures

We will use the outcome data from the longest follow‐up for our primary analysis.

We will include outcomes that are only reported in a single trial.

Primary outcomes

• All‐cause mortality, and proportion of participants with hepatitis B‐related morbidity (number of participants who developed cirrhosis, ascites, variceal bleeding, hepatorenal syndrome, hepatocellular carcinoma, or hepatic encephalopathy, but did not die). We will test these outcomes as a composite outcome, as well as individually (mortality or morbidity).

• Health‐related quality of life. We will accept any validated scale used in the trials, such as the Chronic Liver Disease Questionnaire (CLDQ), World Health Organization Quality of Life (WHOQOL), EuroQoL Group Quality of Life Questionnaire based on five dimensions (EQ‐5D), 36‐item Short Form Health Survey (SF‐36), General Well‐Being Scale, Subjective Quality of Life Scale (SQOL), and the Perceived Quality of Life Scale (PQOL). If a trial includes multiple scales in its outcome reporting, we will select the one most frequently used across the included trials.

• Proportion of participants with serious adverse events (defined according to the International Conference on Harmonisation Guidelines for Good Clinical Practice as any untoward medical occurrence that results in death, is life‐threatening (i.e. hepatic decompensation), requires inpatient hospitalisation or prolongation of existing hospitalisation (i.e. depression), results in persistent or significant disability or incapacity, or is a congenital anomaly/birth defect (ICH‐GCP 2016)).

Secondary outcomes

• Mortality due to hepatitis B‐related liver disease

• Proportion of participants with adverse events considered non‐serious (any untoward medical occurrence that does not meet the above criteria for a serious adverse event)

• Proportion of participants without histological improvement

• Proportion of participants with detectable HBV‐DNA in serum or plasma

• Proportion of participants with detectable HBsAg in serum or plasma

• Proportion of participants with detectable HBeAg in serum or plasma (only relevant for HBeAg‐positive participants)

• Proportion of participants without HBeAg seroconversion in serum or plasma (only relevant for HBeAg‐positive participants)

• Proportion of participants without normalisation of transaminases (i.e. biochemical response)

Search methods for identification of studies

To minimise bias in our search results, we will follow the guidance in Chapter 4 of the Cochrane Handbook for Systematic Reviews of Interventions (Lefebvre 2022a), and in PRISMA‐S (Rethlefsen 2021), to plan and describe the search process for the review. We will complete the search strategies and the literature retrieval with the guidance of the Cochrane Hepato‐Biliary Group's information specialist. We will not set any restrictions on the publication language, year, or status.

Electronic searches

We will search the Cochrane Hepato‐Biliary Group Controlled Trials Register, which will be searched internally by the Cochrane Hepato‐Biliary Group information specialist, via the Cochrane Register of Studies‐Web (CRS‐Web). We will also search the Cochrane Central Register of Controlled Trials (CENTRAL) in the Cochrane Library, MEDLINE Ovid, Embase Ovid (Excerpta Medica Database), LILACS (Latin American and Caribbean Health Science Information database; VHL Regional Portal), Science Citation Index Expanded, and Conference Proceedings Citation Index ‐ Science. The latter two will be searched simultaneously through the Web of Science.

Appendix 1 provides the search strategies for the respective databases, with the expected date range of the searches. We will provide the actual date of the electronic searches at the review stage.

Searching other resources

We will search online trial registries, such as the US National Institutes of Health Ongoing Trials Register ClinicalTrials.gov (clinicaltrials.gov), European Medicines Agency (www.ema.europa.eu), World Health Organization International Clinical Trials Registry Platform (www.who.int/ictrp), US Food and Drug Administration (www.fda.gov), and pharmaceutical company sources, for ongoing or unpublished trials (Lefebvre 2022a).

We will use the PubMed/MEDLINE 'similar articles search' tool on all included studies. We will manually check citations and reference lists of the included studies, and any relevant systematic reviews identified in the database search.

We will search for relevant grey literature sources, such as reports, dissertations, theses, and conference abstracts, e.g. in Google Scholar.

We will also contact authors of identified trials for additional published or unpublished trials.

We will check if there are retraction statements and errata of information for eligible trials, as errata can reflect limitations or even fatal flaws (Lefebvre 2022b).

We will provide the actual date of searching other sources at the review stage. We will use items relevant to our review items from the PRISMA‐S checklist to ensure that we have reported and documented our searches as advised (PRISMA-S Checklist; Rethlefsen 2021).

Data collection and analysis

We will conduct the review in accordance to the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2022a). We will perform the analyses using Review Manager Web (RevMan Web 2023). We will use Trial Sequential Analysis software to conduct sensitivity analysis of the assessment of imprecision with GRADE (Thorlund 2017; TSA 2021).

Selection of studies

Two review authors (HL, CW) will independently screen the titles and abstracts. We will record reports as 'retrieve' (eligible, potentially eligible, or unclear) or 'do not retrieve'. We will independently screen the full texts of potentially eligible trials for inclusion or exclusion, and we will record the reasons for exclusion of the ineligible trials. We will resolve disagreements through discussion, or if needed, we will consult a third review author (LC). We will exclude duplicates with EndNote software (EndNote 2018). We will record the selection process in sufficient detail to complete a PRISMA flow diagram (Page 2021a; Page 2021b).

If, during the selection of trials obtained through our searches for randomised clinical trials, we identify controlled (quasi‐randomised or controlled studies) or observational studies (cohort studies or case reports) on the topic of our review that reported adverse events during the study period, we will include them for a review of the reported adverse events only. We will present these data separately in a table, with a few lines at the end of the Results section, or in the Discussion. We will not run a systematic search for controlled or observational studies for inclusion in this review, which is a limitation. We are aware that by not looking for all controlled or observational studies on adverse events, we allow the risks of putting more weight on potential benefits than on potential harms, and of overlooking uncommon and late adverse events (Storebø 2018).

Data extraction and management

We will use a pre‐piloted data collection form to record study characteristics and outcomes. Two review authors (HL, CW) will independently extract data required for the performance of our review, from the included trials. A summary of the data is presented below.

• Methods: trial design, total treatment duration, number of trial centres and location, and number of withdrawals/dropouts

• Participants: number, mean age, sex, diagnostic criteria, previous antiviral treatment, baseline data, i.e. HBsAg level, HBV DNA level, and HBeAg status, HBV genotype and variants, inclusion criteria, and exclusion criteria

• Interventions: combination regimen (i.e. de novo combination, pegylated interferon with add‐on tenofovir, and tenofovir with add‐on pegylated interferon), dosage, route of administration, duration of treatment, and follow‐up duration

• Comparators: tenofovir monotherapy, dosage, route of administration, duration of treatment, and duration of follow‐up

• Outcomes and time: primary and secondary outcomes specified and collected, and their time points reported

• Notes: dates of trial authors contacted and dates of replies received, source of funding, conflicts of interest of trial authors, clinical trial registration number, a priori sample size estimation, and ethics committee approval (for trials launched after 2005)

In the characteristics of included studies table, we will record whether outcome data were reported in a usable way. We will resolve disagreements through discussion with all review authors. One review author (HL) will enter the data into the characteristics of included studies table in Review Manager Web (RevMan Web 2023). CW will check the data for accuracy.

We will use Plot Digitizer software to extract data from the figures, if they are only presented in figures (Plot Digitizer 2015).

Assessment of risk of bias in included studies

Two review authors (HL, CW) will independently assess the risk of bias using the RoB 2 tool, and follow the guidance in the Cochrane Handbook for Systematic Reviews of Intervention (Higgins 2022b; Sterne 2019). We will resolve disagreements through discussion with a third review author (LC).

We will assess the effect of assignment to the intervention based on the intention‐to‐treat principle, which includes all randomised participants regardless of the interventions that they actually received.

We will use the following five domains to assess the risk of bias in the trials.

• Bias from the randomisation process

• Bias due to deviations from intended interventions

• Bias due to missing outcome data

• Bias in measurement of the outcome

• Bias in selection of the reported results

We will use the signalling questions of each domain to judge the risk of bias. The options for the signalling questions are as follows:

• Yes;

• Probably yes;

• No;

• Probably no;

• No information.

The judgement options include low risk of bias, some concerns, and high risk of bias (Higgins 2022b; Sterne 2019).

• Low risk of bias: the study is judged at low risk of bias in all domains for this outcome result.

• Some concerns: the study is judged to have some concerns in at least one domain for this outcome result, but is not at high risk of bias in any of the remaining domains.

• High risk of bias: the study is judged at high risk of bias in at least one domain for this outcome result, or the study is judged to have some concerns for multiple domains in a way that substantially lowers confidence in the result.

We will use the most recent RoB 2 Excel tool, which is available from www.riskofbias.info, to record the answers to the signalling questions and risk of bias judgements (Sterne 2019). The outcomes will be extracted directly to the risk of bias table. We will present a summary of the risk of bias assessments with the results of each trial included in a meta‐analysis in the forest plot, which will give a visual impression of each trial’s contribution at different levels of risk of bias, especially when considered in combination with each trial’s weight (Boutron 2022). These data will be presented at the review stage as supplementary material in the Open Science Framework platform (www.osf.io). When assessing cluster‐randomised trials, we will use the most recent guidance at www.riskofbias.info/welcome/rob-2-0-tool/rob-2-for-cluster-randomized-trials. We will assess the risk of bias trials in cross‐over trials as in trials with parallel group design, as we will use the data from the first period only, i.e. before the cross‐over (Higgins 2022c).

The risk of bias assessment will feed into one domain of the GRADE approach for assessing the certainty of a body of evidence (Schünemann 2022a).

We will assess the risk of bias of the three primary outcomes: all‐cause mortality and proportion of participants with hepatitis B‐related morbidity, quality of life, and proportion of participants with serious adverse events, at the longest follow‐up. When assessing the risk of bias in measurement of the outcome for quality of life and proportion of participants with serious adverse events, we will consider who the outcome assessor was, and judge the implications for risk of bias if the outcome assessor was aware of the intervention assignment.

We will present the three outcomes in a summary of findings table, as these outcomes are the most clinically relevant for clinical practice and people with chronic hepatitis B.

Assessment of bias in conducting the systematic review

We will conduct the review according to this published protocol, and report the differences between this published protocol and a completed review.

Measures of treatment effect

We will use Review Manager Web to analyse data (RevMan Web 2023). We will calculate the risk ratio (RR) with 95% confidence intervals (CIs) for dichotomous data (i.e. adverse events). If the data are reported as count data (incidence rate), we will report the events with rate ratio and 95% CI. If the trials used the same measurement scales for continuous data, we will calculate the mean difference (MD) with 95% CIs; and if the trials used different measurement scales (e.g. for health‐related quality of life), we will calculate the standard mean difference (SMD) with 95% CIs. The interpretation of SMD is as follows (Schünemann 2022b):

• SMD less than 0.40 for small intervention effects;

• SMD between 0.40 and 0.70 for moderate intervention effects;

• SMD greater than 0.70 for large intervention effects.

In some scales, the score increases with disease severity (e.g. a higher score indicates a more severe condition), and in others, the score behaves in the opposite direction (e.g. a higher score indicates a less severe condition). As the SMD method does not correct for differences in the direction of the scale, if necessary, we will multiply the mean values from one set of studies by ‐1 (or subtract the mean from the maximum possible value for the scale) to ensure that all the scales point in the same direction before standardisation (Higgins 2022d).

We will describe skewed data in a narrative format. We will use intention‐to‐treat analyses, instead of per‐protocol analyses, if possible. When only per‐protocol analyses are reported, we will use and record them in the review. If neither intention‐to‐treat analyses nor per‐protocol analyses can be used, we will use the available data in the original trials. If data are not reported in a format that we can use, we will attempt to convert the data to the required format, following the guidance in Chapter 6 of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2022d).

Unit of analysis issues

The unit of analysis is the participant with chronic HBV infection randomised to the parallel groups. We will record how trials presented outcome data (i.e. the total number of participants with an event). For dichotomous outcomes (i.e. adverse events), we will use participants as the unit of analysis, instead of events (i.e. number of participants with adverse events (Higgins 2022c)). However, if adverse events are reported as count data (incidence rate), we will analyse the rate ratios based on events instead of participants (Higgins 2022d). We will report situations in which multiple events in a participant were incorrectly treated as independent, without considering the interdependence of the events (Higgins 2022d).

If a trial has multiple experimental groups, we will only include the data from the experimental group(s) relevant to the objective of our review. We will separately compare each of the relevant experimental groups with each half of the control group if within the same comparison, to avoid double‐counting (Higgins 2022c). For example, in the case of experimental group 1 versus experimental group 2 versus control group, we will halve the control group. We will list all experimental group(s) in the characteristics of included studies table, even if we do not use them in the review.

In cluster‐randomised trials, the unit of analysis is a group of participants as randomised (e.g. schools, villages, medical practices, or families (Deeks 2022)). In cross‐over trials, we will only include data from the first phase to avoid period effect or carry‐over effect (Higgins 2022d).

Dealing with missing data

We will contact authors by email for missing data or information that was unclear in the original studies. If possible, we will use intention‐to‐treat data for analysis. Otherwise, we will use the available data in the original trials. If some participants have missing data for the primary outcomes, we will assume that the data are missing at random, or as a poor outcome (Heymans 2022). We will follow the guidance of the Cochrane Handbook for Systematic Reviews of Interventions to assess the risk of bias due to missing outcome data (Deeks 2022). We will take the worst case and best case analyses into account for the extreme boundaries (Hollis 1999).

• Best‐worst case scenario: in the experimental group, there are no dropouts/participants lost, but all the dropouts/participants lost from the control group have outcome data. This assumption favours the experimental intervention.

• Worst‐best case scenario: all the dropouts/participants lost are from the experimental group, but none in the control group have missing outcome data. This assumption favours the control intervention.

We will perform sensitivity analysis to examine the extent of uncertainty due to attrition bias (i.e. dropouts, losses to follow‐up, and withdrawals). If the data are likely to be normally distributed, we will use the median when the mean is not available (Higgins 2022d). If standard deviations (SD) are missing for continuous data, we will ask the trial authors about the availability of data by email. We will not impute missing SDs. If the impact of missing data is significant, we will record it in the review.

Assessment of heterogeneity

We will take all possible heterogeneity into account, including clinical, methodological, and statistical heterogeneity. We will assess the clinical and methodological heterogeneity according to the study characteristics. We will visually inspect forest plot graphs to investigate the possibility of statistical heterogeneity. We will use a P value of less than 0.10 to indicate statistical heterogeneity; we will further quantify the heterogeneity using the I² statistic, when the P value is less than 0.10 (Deeks 2022).

We will use the I² statistic to assess the statistical heterogeneity according to Cochrane Handbook guidance (Deeks 2022).

• 0% to 40%: might not be important

• 30% to 60%: may represent moderate heterogeneity

• 50% to 90%: may represent substantial heterogeneity

• 75% to 100%: considerable heterogeneity

If we find substantial heterogeneity, i.e. I² > 50%, we will record it and explore the possible reasons by performing subgroup analyses.

We will not use the simple thresholds to interpret statistical heterogeneity, because there is uncertainty around the I² statistic when there are few trials (Deeks 2022). We will use the I² statistic and the Chi² test P value to assess statistical heterogeneity.

Assessment of reporting biases

We will create a funnel plot to assess possible small‐study effects and publication bias if there are more than 10 trials in a meta‐analysis (Deeks 2022). We will perform Egger's test to assess the asymmetry (Egger 1997).

Data synthesis

If there are at least two trials with similar clinical characteristics (i.e. participants, interventions, comparisons, and outcomes), we will perform meta‐analysis to assess the results, using Review Manager Web (RevMan Web 2023). We will not limit our primary analysis to trials at overall low risk of bias, but we will use sensitivity analyses to present data only from trials at low risk of bias. We will use a random‐effects model for our main analysis and a fixed‐effect model for a sensitivity analysis. If there is a significant difference between the results produced by the two models, we will report it. According to the Cochrane Handbook for Systematic Reviews of Interventions, we will perform quantitative synthesis and illustrate the results by forest plots (Deeks 2022). We will present all results with 95% CIs.

If the included trials are not suitable for meta‐analysis, or there are not enough data for meta‐analysis, we will present the outcome data in a descriptive format, according to the Cochrane Handbook for Systematic Reviews of Interventions (McKenzie 2022).

Subgroup analysis and investigation of heterogeneity

Based on the information in the background of our review, we will carry out the following subgroup analyses, if there are at least five trials providing data for an outcome.

• Trials at low risk of bias, or at low risk of bias, or with some concerns compared to trials at high risk of bias, because trials at high risk of bias may overestimate beneficial intervention effects or underestimate harmful intervention effects (Boutron 2022);

• Trials without for‐profit funding compared to trials with some concerns or at risk of for‐profit funding, because conflicts of interest can introduce bias, including publication bias (Lundh 2017)

• Comparing combination regimens, i.e. de novo combination compared to add‐on strategy, because a previous meta‐analysis showed that possibly more participants receiving the add‐on combination strategy would achieve a HBsAg loss compared with the de novo combination (Qiu 2018)

• HBeAg status, i.e. HBeAg‐positive compared to HBeAg‐negative participants, because the levels of HBsAg and HBV DNA are different between HBeAg‐positive and HBeAg‐negative participants (Lok 2017)

If necessary, we will perform meta‐regression analyses to investigate the source of heterogeneity. We will test subgroup interactions in Review Manager Web (RevMan Web 2023).

Sensitivity analysis

We will carry out the following sensitivity analyses to assess the robustness of results.

• Excluding trials having some concerns or those at high risk of bias

• Best‐worse case scenario analysis, described in Dealing with missing data

• Worse‐best case scenario analysis, described in Dealing with missing data

• Excluding trials with missing data, as defined in Dealing with missing data

• Assessment of imprecision with Trial Sequential Analysis

Trial Sequential Analysis

We will use Trial Sequential Analysis to calculate the diversity‐adjusted required information size (DARIS) to make a firm conclusion, and to control random errors in our meta‐analyses (Brok 2008; Brok 2009; Thorlund 2009; Thorlund 2010; Thorlund 2017; TSA 2021; Wetterslev 2008; Wetterslev 2009; Wetterslev 2017).

We will add the trials according to year of publication. If more than one trial is published during the same year, we will add trials alphabetically according to the last name of the first author. We will construct trial sequential monitoring boundaries on the basis of the required information size (Jakobsen 2014; Thorlund 2017). These boundaries determine the statistical inference that one may draw regarding the cumulative meta‐analysis that has not reached the DARIS; if the trial sequential monitoring boundary is crossed before the required information size is reached, firm evidence may be established, and further trials may be superfluous. In contrast, if the boundary is not surpassed, it is most likely necessary to continue conducting trials to detect or reject a certain intervention effect. This can be determined by assessing whether the cumulative Z‐curve crosses the trial sequential monitoring boundary for futility.

For dichotomous outcomes, we will calculate the required information size based on: the event proportion in the control group of the included trials; the assumption of a plausible risk ratio reduction of 20%; a risk of type I error of 2.5%, due to the three primary outcomes (Jakobsen 2014); a risk of type II error of 10%; and the diversity of the included trials in the meta‐analysis. For the continuous outcome, health‐related quality of life, we will calculate the required information size using a minimal relevant difference of half the SD of the meta‐analysis; type I error of 2.5%, due to the three primary outcomes (Jakobsen 2014); type II error of 10%; and diversity of 10% (Wetterslev 2009). We will use the random‐effects model for the meta‐analysis.

We will not perform Trial Sequential Analysis on the secondary outcomes of our review.

In Trial Sequential Analysis, if the accrued number of participants is below 50% of the DARIS, we will downgrade the assessment of imprecision by two levels; if the accrued number of participants is 50% to 100% of the DARIS, we will downgrade the assessment of imprecision by one level; and if the futility or DARIS is reached, we will not downgrade the assessment of imprecision. We will perform this analysis with Trial Sequential Analysis software, version 0.9.5.10 beta (TSA 2021).

Summary of findings and assessment of the certainty of the evidence

According to the recommendations of the Cochrane Handbook for Systematic Reviews of Interventions, we will use the online GRADEpro GDP software to construct one summary of findings table for the combination of tenofovir and pegylated interferon compared to tenofovir monotherapy (GRADEpro GDT; Schünemann 2022a).

We will present the certainty of evidence of the outcome results of all‐cause mortality and proportion of participants with hepatitis B‐related morbidity, health‐related quality of life, and proportion of participants with serious adverse events, at the longest follow‐up, providing the median or mean, and the range of follow‐up in the trials.

Two review authors (HL, CW) will independently assess the certainty of the evidence using the GRADE approach. The GRADE domains encompass risk of bias, inconsistency of results, indirectness of evidence, imprecision of results, and publication bias (Schünemann 2013). We will justify all decisions to downgrade the trial results using footnotes and comments whenever needed, to help the reader understand our assessments.

We will use the overall judgement for an outcome result for risk of bias. We will resolve any discrepancies by discussion with a third review author (LC), and a consensus will be reached with the corresponding author (XQ). There are four levels of certainty of the evidence.

• High certainty: we are very confident that the true effect lies close to that of the estimate of the effect

• Moderate certainty: we are moderately confident in the effect estimate; the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different

• Low certainty: our confidence in the effect estimate is limited; the true effect may be substantially different from the estimate of the effect

• Very low certainty: we have very little confidence in the effect estimate; the true effect is likely to be substantially different from the estimate of effect

Appendices

Appendix 1. Search strategies

Database	Date range	Search strategy
The Cochrane Hepato‐Biliary Group Controlled Trials Register (via the Cochrane Register of Studies Web)	Date of search will be given at review stage	(tenofovir or viread or vemlidy or Tavin or tenof or hepdoze or tentide or PMPA or TDF or TAF) and (Interferon* or intron or roferon or pegas*s or pegintron or viraferonpeg or peginterferon or peg‐ifn or interferon‐alpha) and ((chronic and (hepatitis b or hep b or hbv)) or HBsAg or HBeAg)
Cochrane Central Register of Controlled Trials in the Cochrane Library	Latest issue	#1 MeSH descriptor: [Tenofovir] explode all trees #2 (tenofovir or viread or vemlidy or Tavin or tenof or hepdoze or tentide or PMPA or TDF or TAF) #3 #1 or #2 #4 MeSH descriptor: [Antiviral Agents] explode all trees #5 MeSH descriptor: [Polyethylene Glycols] explode all trees #6 (Interferon* or intron or roferon or pegas*s or pegintron or viraferonpeg or peginterferon or peg‐ifn or interferon‐alpha) #7 #4 or #5 or #6 #8 MeSH descriptor: [Hepatitis B, Chronic] this term only #9 ((chronic and (hepatitis b or hep b or hbv)) or HBsAg or HBeAg) #10 #8 or #9 #11 #3 and #7 and #10
MEDLINE Ovid	1946 to date of search	1. exp Tenofovir/ 2. (tenofovir or viread or vemlidy or Tavin or tenof or hepdoze or tentide or PMPA or TDF or TAF).mp. [mp=title, book title, abstract, original title, name of substance word, subject heading word, floating sub‐heading word, keyword heading word, organism supplementary concept word, protocol supplementary concept word, rare disease supplementary concept word, unique identifier, synonyms] 3. 1 or 2 4. exp Antiviral Agents/ 5. exp Polyethylene Glycols/ 6. (Interferon* or intron or roferon or pegas*s or pegintron or viraferonpeg or peginterferon or peg‐ifn or interferon‐alpha).mp. [mp=title, book title, abstract, original title, name of substance word, subject heading word, floating sub‐heading word, keyword heading word, organism supplementary concept word, protocol supplementary concept word, rare disease supplementary concept word, unique identifier, synonyms] 7. 4 or 5 or 6 8. Hepatitis B, Chronic/ 9. ((chronic and (hepatitis b or hep b or hbv)) or HBsAg or HBeAg).mp. [mp=title, book title, abstract, original title, name of substance word, subject heading word, floating sub‐heading word, keyword heading word, organism supplementary concept word, protocol supplementary concept word, rare disease supplementary concept word, unique identifier, synonyms] 10. 8 or 9 11. 3 and 7 and 10 12. (randomized controlled trial or controlled clinical trial or retracted publication or retraction of publication).pt. 13. random* or placebo*.ab. 14. trial.ti. 15. 12 or 13 or 14 16. 11 and 15
Embase Ovid	1974 to date of search	1. tenofovir/ 2. (tenofovir or viread or vemlidy or Tavin or tenof or hepdoze or tentide or PMPA or TDF or TAF).mp. [mp=title, abstract, heading word, drug trade name, original title, device manufacturer, drug manufacturer, device trade name, keyword heading word, floating subheading word, candidate term word] 3. 1 or 2 4. exp peginterferon/ 5. (Interferon* or intron or roferon or pegas*s or pegintron or viraferonpeg or peginterferon or peg‐ifn).mp. [mp=title, abstract, heading word, drug trade name, original title, device manufacturer, drug manufacturer, device trade name, keyword heading word, floating subheading word, candidate term word] 6. 4 or 5 7. chronic hepatitis B/ 8. ((chronic and (hepatitis b or hep b or hbv)) or HBsAg or HBeAg).mp. [mp=title, abstract, heading word, drug trade name, original title, device manufacturer, drug manufacturer, device trade name, keyword heading word, floating subheading word, candidate term word] 9. 7 or 8 10. 3 and 6 and 9 11. ‘Randomized controlled trial’ or ‘Controlled clinical study’ or ‘randomization’ or ‘intermethod comparison’ or ‘double blind procedure’ or ‘human experiment’ or ‘retracted article’ 12. (compare or compared or comparison or trial).ti. 13. ((evaluated or evaluate or evaluating or assessed or assess) and (compare or compared or comparing or comparison) and (random* or placebo*)).ab. 14. 11 or 12 or 13 15. 10 and 14
LILACS (VHL Regional Portal)	1982 to date of search	((tenofovir OR viread OR vemlidy OR tavin OR tenof OR hepdoze OR tentide OR pmpa OR tdf OR taf)) AND ((interferon* OR intron OR roferon OR pegas*s OR pegintron OR viraferonpeg OR peginterferon OR peg‐ifn)) AND (((chronic AND (hepatitis b OR hep b OR hbv)) OR hbsag OR hbeag)) AND ( db:("LILACS"))
Science Citation Index Expanded (Web of Science)	1900 to date of search	#6 #4 AND #5 #5 TI=(random* or blind* or placebo* or meta‐analys* or trial*) OR TS=(random* or blind* or placebo* or meta‐analys*) #4 #3 AND #2 AND #1 #3 TS=((chronic and (hepatitis b or hep b or hbv)) or HBsAg or HBeAg) #2 TS=(Interferon* or intron or roferon or pegas*s or pegintron or viraferonpeg or peginterferon or peg‐ifn) #1 TS=(tenofovir or viread or vemlidy or Tavin or tenof or hepdoze or tentide or PMPA or TDF or TAF)
Conference Proceedings Citation Index – Science (Web of Science)	1990 to date of search	#6 #4 AND #5 #5 TI=(random* or blind* or placebo* or meta‐analys* or trial*) OR TS=(random* or blind* or placebo* or meta‐analys*) #4 #3 AND #2 AND #1 #3 TS=((chronic and (hepatitis b or hep b or hbv)) or HBsAg or HBeAg) #2 TS=(Interferon* or intron or roferon or pegas*s or pegintron or viraferonpeg or peginterferon or peg‐ifn) #1 TS=(tenofovir or viread or vemlidy or Tavin or tenof or hepdoze or tentide or PMPA or TDF or TAF)

Contributions of authors

Conceived the protocol: Xingshun Qi

Drafted the protocol: Hui Li, Xingshun Qi

Revised the protocol: Hui Li, Cai'e Wang, Lu Chai, Xingshun Qi

All authors agreed on the current protocol version for publication.

Sources of support

Internal sources

• Department of Gastroenterology, General Hospital of Northern Theater Command, Shenyang, China

  This review was supported by Department of Gastroenterology, General Hospital of Northern Theater Command, Shenyang, China.

External sources

• Cochrane Hepato‐Biliary Group, Denmark

  Help with the protocol preparation, search strategies design, and editorial processes

Declarations of interest

LH: none known

WC: none known

CL: none known

QX: none known

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