When to Monitor CD4 Cell Count and HIV RNA to Reduce Mortality and AIDS-Defining Illness in Virologically Suppressed HIV-Positive Persons on Antiretroviral Therapy in High-Income Countries: A Prospective Observational Study

Target Trial Emulation to Improve Causal Inference from Observational Data: What, Why, and How?

ABSTRACT

Target trial emulation has drastically improved the quality of observational studies investigating the effects of interventions. Its ability to prevent avoidable biases that have plagued many observational analyses has contributed to its recent popularity. This review explains what target trial emulation is, why it should be the standard approach for causal observational studies that investigate interventions, and how to do a target trial emulation analysis. We discuss the merits of target trial emulation compared with often used, but biased analyses, as well as potential caveats, and provide clinicians and researchers with the tools to better interpret results from observational studies investigating the effects of interventions.

Comparative effectiveness of urine drug screening strategies alongside opioid agonist treatment in British Columbia, Canada: a population-based observational study protocol

INTRODUCTION

Urine drug tests (UDTs) are commonly used for monitoring opioid agonist treatment (OAT) responses, supporting the clinical decision for take-home doses and monitoring potential diversion. However, there is limited evidence supporting the utility of mandatory UDTs-particularly the impact of UDT frequency on OAT retention. Real-world evidence can inform patient-centred approaches to OAT and improve current strategies to address the ongoing opioid public health emergency. Our objective is to determine the safety and comparative effectiveness of alternative UDT monitoring strategies as observed in clinical practice among OAT clients in British Columbia, Canada from 2010 to 2020.

METHODS AND ANALYSIS

We propose a population-level retrospective cohort study of all individuals 18 years of age or older who initiated OAT from 1 January 2010 to 17 March 2020. The study will draw on eight linked health administrative databases from British Columbia. Our primary outcomes include OAT discontinuation and all-cause mortality. To determine the effectiveness of the intervention, we will emulate a 'per-protocol' target trial using a clone censoring approach to compare fixed and dynamic UDT monitoring strategies. A range of sensitivity analyses will be executed to determine the robustness of our results.

ETHICS AND DISSEMINATION

The protocol, cohort creation and analysis plan have been classified and approved as a quality improvement initiative by Providence Health Care Research Ethics Board and the Simon Fraser University Office of Research Ethics. Results will be disseminated to local advocacy groups and decision-makers, national and international clinical guideline developers, presented at international conferences and published in peer-reviewed journals electronically and in print.

Causal analyses with target trial emulation for real-world evidence removed large self-inflicted biases: systematic bias assessment of ovarian cancer treatment effectiveness

BACKGROUND AND OBJECTIVES

Drawing causal conclusions from real-world data (RWD) poses methodological challenges and risk of bias. We aimed to systematically assess the type and impact of potential biases that may occur when analyzing RWD using the case of progressive ovarian cancer.

METHODS

We retrospectively compared overall survival with and without second-line chemotherapy (LOT2) using electronic medical records. Potential biases were determined using directed acyclic graphs. We followed a stepwise analytic approach ranging from crude analysis and multivariable-adjusted Cox model up to a full causal analysis using a marginal structural Cox model with replicates emulating a reference randomized controlled trial (RCT). To assess biases, we compared effect estimates (hazard ratios [HRs]) of each approach to the HR of the reference trial.

RESULTS

The reference trial showed an HR for second line vs. delayed therapy of 1.01 (95% confidence interval [95% CI]: 0.82-1.25). The corresponding HRs from the RWD analysis ranged from 0.51 for simple baseline adjustments to 1.41 (95% CI: 1.22-1.64) accounting for immortal time bias with time-varying covariates. Causal trial emulation yielded an HR of 1.12 (95% CI: 0.96-1.28).

CONCLUSION

Our study, using ovarian cancer as an example, shows the importance of a thorough causal design and analysis if one is expecting RWD to emulate clinical trial results.

The Future of Causal Inference

The past several decades have seen exponential growth in causal inference approaches and their applications. In this commentary, we provide our top-10 list of emerging and exciting areas of research in causal inference. These include methods for high-dimensional data and precision medicine, causal machine learning, causal discovery, and others. These methods are not meant to be an exhaustive list; instead, we hope that this list will serve as a springboard for stimulating the development of new research.

A Two-stage Approach for Rapid Assessment of the Proportion Achieving Viral Suppression Using Routine Clinical Data

BACKGROUND

Improving viral suppression among people with HIV reduces morbidity, mortality, and transmission. Accordingly, monitoring the proportion of patients with a suppressed viral load is important to optimizing HIV care and treatment programs. But viral load data are often incomplete in clinical records. We illustrate a two-stage approach to estimate the proportion of treated people with HIV who have a suppressed viral load in the Dominican Republic.

METHODS

Routinely collected data on viral load and patient characteristics were recorded in a national database, but 74% of patients on treatment at the time of the study did not have a recent viral load measurement. We recruited a subset of these patients for a rapid assessment that obtained additional viral load measurements. We combined results from the rapid assessment and main database using a two-stage weighting approach and compared results to estimates obtained using standard approaches to account for missing data.

RESULTS

Of patients with recent routinely collected viral load data, 60% had a suppressed viral load. Results were similar after applying standard approaches to account for missing data. Using the two-stage approach, we estimated that 77% (95% confidence interval [CI] = 74, 80) of those on treatment had a suppressed viral load.

CONCLUSIONS

When assessing the proportion of people on treatment with a suppressed viral load using routinely collected data, applying standard approaches to handle missing data may be inadequate. In these settings, augmenting routinely collected data with data collected through sampling-based approaches could allow more accurate and efficient monitoring of HIV treatment program effectiveness.

Comparative Effectiveness of Opioid Tapering or Abrupt Discontinuation vs No Dosage Change for Opioid Overdose or Suicide for Patients Receiving Stable Long-term Opioid Therapy

IMPORTANCE

Opioid dosage tapering has emerged as a strategy to reduce harms associated with long-term opioid therapy; however, evidence supporting this approach is limited.

OBJECTIVE

To identify the association of opioid tapering or abrupt discontinuation with opioid overdose and suicide events among patients receiving stable long-term opioid therapy without evidence of opioid misuse.

DESIGN, SETTING, AND PARTICIPANTS

This comparative effectiveness study with a trial emulation approach used a large US claims data set of individuals with commercial insurance or Medicare Advantage who were aged 18 years or older and receiving stable long-term opioid therapy without evidence of opioid misuse between January 1, 2010, and December 31, 2018. Statistical analysis was performed from January 17, 2020, through November 12, 2021.

INTERVENTIONS

Three opioid dosage strategies: stable dosage, tapering (dosage reduction ≥15%), or abrupt discontinuation.

MAIN OUTCOMES AND MEASURES

Time to opioid overdose or suicide event identified from International Classification of Diseases, Ninth Revision and International Statistical Classification of Diseases and Related Health Problems, Tenth Revision diagnosis codes in medical claims over 11 months of follow-up. Inverse probability weighting was used to adjust for baseline confounders. The primary analysis used an intention-to-treat approach; follow-up after assignment regardless of changes in opioid dose was included. A per-protocol analysis was also conducted, in which episodes were censored for lack of adherence to assigned treatment.

RESULTS

A cohort of 199 836 individuals (45.1% men; mean [SD] age, 56.9 [12.4] years; and 57.6% aged 45-64 years) had 415 123 qualifying, long-term opioid therapy episodes; 87.1% of episodes were considered stable, 11.1% were considered a taper, and 1.8% were considered abrupt discontinuation. The adjusted cumulative incidence of opioid overdose or suicide events 11 months after baseline was 0.96% (95% CI, 0.92%-0.99%) with a stable dosage strategy, 1.10% (95% CI, 0.99%-1.22%) with a tapered dosage strategy, and 1.28% (95% CI, 0.93%-1.38%) with an abrupt discontinuation strategy. The risk difference between a taper and a stable dosage was 0.15% (95% CI, 0.03%-0.26%), and the risk difference between abrupt discontinuation and a stable dosage was 0.33% (95% CI, -0.03% to 0.74%). Results were similar using the per-protocol approach.

CONCLUSIONS AND RELEVANCE

This study identified a small absolute increase in risk of harms associated with opioid tapering compared with a stable opioid dosage. These results do not suggest that policies of mandatory dosage tapering for individuals receiving a stable long-term opioid dosage without evidence of opioid misuse will reduce short-term harm via suicide and overdose.

A comparative analysis and review of how national guidelines for chronic disease monitoring are made in low- and middle-income compared to high-income countries

Background

Understanding how clinical practice guidelines and recommendations are adopted in high-income and low-income settings will help contextualise the value and validity of recommendations in different settings. We investigate how major guidelines and recommendations are developed for management and monitoring of post-diagnosis treatment for three important chronic diseases: HIV, hypertension and type 2 diabetes mellitus (T2DM).

Methods

Eligible guidelines were searched for using PubMed, Google, and health ministry websites for all three conditions. Only guidelines published from 2010 to 2020 were included. The source of the guidelines, year of most recent guideline, and basis of the guidelines were assessed. Additionally, recommendations, the strength of the recommendation and the quality of the evidence for treatment goals of non-pregnant adults and the frequency of monitoring were also extracted and assessed.

Results

Of the 42 countries searched 90%, 71% and 60% had T2DM, hypertension and HIV guidelines outlining targets for long-term management, respectively. Most T2DM guidelines recommend an HbA1c target of ≤7.0% (68%) or ≤6.5% (24%) as the ideal glycaemic target for most non-pregnant adults, while hypertension guidelines recommend blood pressure (systolic blood pressure/diastolic blood pressure) targets of <140/90 mm Hg (94%) and <130/80 mm Hg (6%). Of the identified HIV guidelines, 67% define virological failure as a viral load >1000 copies/mL, with 26%, mostly HICs, defining virological failure as a viral load >200 copies/mL. Recommendations for the frequency of monitoring for any diagnosed patients were available in 18 (55%) of the hypertension guidelines, 25 (93%) of HIV guidelines, and 27 (73%) of the T2DM guidelines. Only a few of the guidelines provide the strength of the recommendation and the quality of the evidence.

Conclusions

Most guidelines from LMICs are adopted or adapted from existing HIC guidelines or international and regional organisation guidelines with little consideration for resource availability, contextual factors, logistical issues and general feasibility.

Exploiting nonsystematic covariate monitoring to broaden the scope of evidence about the causal effects of adaptive treatment strategies

In studies based on electronic health records (EHR), the frequency of covariate monitoring can vary by covariate type, across patients, and over time, which can limit the generalizability of inferences about the effects of adaptive treatment strategies. In addition, monitoring is a health intervention in itself with costs and benefits, and stakeholders may be interested in the effect of monitoring when adopting adaptive treatment strategies. This paper demonstrates how to exploit nonsystematic covariate monitoring in EHR-based studies to both improve the generalizability of causal inferences and to evaluate the health impact of monitoring when evaluating adaptive treatment strategies. Using a real world, EHR-based, comparative effectiveness research (CER) study of patients with type II diabetes mellitus, we illustrate how the evaluation of joint dynamic treatment and static monitoring interventions can improve CER evidence and describe two alternate estimation approaches based on inverse probability weighting (IPW). First, we demonstrate the poor performance of the standard estimator of the effects of joint treatment-monitoring interventions, due to a large decrease in data support and concerns over finite-sample bias from near-violations of the positivity assumption (PA) for the monitoring process. Second, we detail an alternate IPW estimator using a no direct effect assumption. We demonstrate that this estimator can improve efficiency but at the potential cost of increase in bias from violations of the PA for the treatment process.

Adherence to antiretroviral therapy among HIV infected pregnant women in public health sectors: a pilot of Chilenje level one Hospital Lusaka, Zambia

Introduction

regular use of Antiretroviral Therapy (ART) in pregnancy and breastfeeding reduces the odds of Mother-to-Child HIV Transmission (MTCT). However, adherence to ART is critical for MTCT to be successful. The present study investigated factors that influence adherence to ART among HIV infected pregnant women in Zambia.

Methods

a cross-sectional study design was conducted involving 71 HIV infected pregnant women who were advised to join the Prevention of Mother-to-Child HIV Transmission (PMTCT) program during their routine Antenatal clinic (ANC) visit and were on ART for more than six months. We used the Medication Possession Ratio (MPR) to quantify adherence levels. We used logistic regression to establish factors that influence adherence to ART.

Results

a total of 71 HIV infected pregnant women with a median age of 27years (IQR, 25-30) were enrolled in the study. There was evidence of a difference in adherence levels between pregnant women above 30 years and ones between 15 years and 30 years (P<0.001). Median adherence levels in this group were found to be at 96%(IQR 89-97). The main predictor of adherence in this population was marital status (being on separation) and age. The women who were on separation were 0.14 times less likely to adhere to option B+ compared to married women.

Conclusion

adherence to option B+ among pregnant women is low. Adherence was significantly influenced by marital status (being on separation) and age. Efforts to improve adherence should be directed towards women on separation and young adults (< 30 years of age).

Associations between baseline characteristics, CD4 cell count response and virological failure on first-line efavirenz + tenofovir + emtricitabine for HIV

OBJECTIVES

The aim of this study was to investigate associations between baseline characteristics and CD4 cell count response on first-line antiretroviral therapy and risk of virological failure (VF) with or without drug resistance.

METHODS

We conducted an analysis of UK Collaborative HIV Cohort data linked to the UK HIV Drug Resistance Database. Inclusion criteria were viral sequence showing no resistance prior to initiation of first-line efavirenz + tenofovir disoproxil fumarate + emtricitabine and virological suppression within 6 months. Outcomes of VF (≥200 copies/mL) with or without drug resistance were assessed using a competing risks approach fitted jointly with a model for CD4 cell count recovery. Hazard ratios for each VF outcome were estimated for baseline CD4 cell count and viral load and characteristics of CD4 cell count response using latent variables on a standard normal scale.

RESULTS

A total of 3640 people were included with 338 VF events; corresponding viral sequences were available in 134 with ≥1 resistance mutation in 36. VF with resistance was associated with lower baseline CD4 (0.30, 0.09-0.62), lower CD4 recovery (0.04, 0.00-0.17) and higher CD4 variability (4.40, 1.22-12.68). A different pattern of associations was observed for VF without resistance, but the strength of these results was less consistent across sensitivity analyses. Cumulative incidence of VF with resistance was estimated to be <2% at 3 years for baseline CD4 ≥350 cells/μL.

CONCLUSION

Lower baseline CD4 cell count and suboptimal CD4 recovery are associated with VF with drug resistance. People with low CD4 cell count before ART or with suboptimal CD4 recovery on treatment should be a priority for regimens with high genetic barrier to resistance.

Effectiveness of Transmitted Drug Resistance Testing Before Initiation of Antiretroviral Therapy in HIV-Positive Individuals

BACKGROUND

For people living with HIV, major guidelines in high-income countries recommend testing for transmitted drug resistance (TDR) to guide the choice of first-line antiretroviral therapy (ART). However, individuals who fail a first-line regimen can now be switched to one of several effective regimens. Therefore, the virological and clinical benefit of TDR testing needs to be evaluated.

METHODS

We included individuals from the HIV-CAUSAL Collaboration who enrolled <6 months of HIV diagnosis between 2006 and 2015, were ART-naive, and had measured CD4 count and HIV-RNA. Follow-up started at the date when all inclusion criteria were first met (baseline). We compared 2 strategies: (1) TDR testing within 3 months of baseline versus (2) no TDR testing. We used inverse probability weighting to estimate the 5-year proportion and hazard ratios (HRs) of virological suppression (confirmed HIV-RNA <50 copies/mL), and of AIDS or death under both strategies.

RESULTS

Of 25,672 eligible individuals (82% males, 52% diagnosed in 2010 or later), 17,189 (67%) were tested for TDR within 3 months of baseline. Of these, 6% had intermediate- or high-level TDR to any antiretroviral drug. The estimated 5-year proportion virologically suppressed was 77% under TDR testing and 74% under no TDR testing; HR 1.06 (95% confidence interval: 1.03 to 1.19). The estimated 5-year risk of AIDS or death was 6% under both strategies; HR 1.03 (95% confidence interval: 0.95 to 1.12).

CONCLUSIONS

TDR prevalence was low. Although TDR testing improved virological response, we found no evidence that it reduced the incidence of AIDS or death in first 5 years after diagnosis.

Is it Safe and Cost Saving to Defer the CD4+ Cell Count Monitoring in Stable Patients on Art with More than 350 or 500 cells/μl?

Background

CD4+ lymphocyte cell count represents the main immunological marker used to monitor HIV infection. However, frequent monitoring may be unnecessary, could cause anxiety to the patient as well as burdening healthcare with extra expenses.

Objectives and methods

A two-step retrospective (safety and cost-saving) analysis was performed to evaluate the probability of maintaining a safe number of more than 350 CD4+ cells/μl in HIV-positive subjects under treatment during a three-year follow up and secondarily to estimate in real life the cost of the CD4+ determinations in a 3 years period, speculating on possible cost-saving strategies. The safety analyses was conducted with Kaplan-Meyer method considering: 1) all patients independently from their viral load (VL); 2) patients with 500 > CD4+ ≥ 350 cells/μl versus (vs) CD4+ ≥ 500 cells/μl at baseline; 3) patients with VL < 20 copies/ml vs VL > 20 copies/ml. The cost-saving analysis measuring the costs of CD4+ determinations was calculated from April 1, 2013, to March 31, 2016.

Results

In the safety analysis, 253 subjects were enrolled. The median CD4+ count was 623 (489–805) cells/μl. Subjects maintaining ≥ 350 cells/μl in the first, second, and third year were respectively 238 (94.1%), 229 (90.5%), and 226 (89.3%), independently from VL. Within subjects with ≥ 350 CD4+/μl vs. ≥ 500 CD4+/μl at baseline, those who maintained ≥ 350 cells/μl until the third year were respectively 241 (95.3%) and 158 (98.1%). The probability of maintaining these values in the third year was 89.3% for those who had CD4+ ≥ 350/μl at baseline and 98.1% for those who had CD4+ ≥ 500/μl. This probability was around 90% vs. 99% for subjects with HIV-RNA above or below 20 copies/ml. In the real-life cost saving analysis, we evaluated subjects with a stable value or more than 500 CD4+ (respectively 343, 364 and 383 in the first, second and third period). We observed mean value of about two determinations patient/year (2.41 in 2013/2014; 2.32 in 2014/2015; 2.18 in 2015/2016), with a significant decrease between the first and the last period (p<0.001). The mean cost patient/year was €101.51 in the first year, €97.61 in the second, €92.00 in the third (p<0,001). Assuming to extend these procedures to all our patients with stable CD4+ cells/μl and monitoring CD4+ cell count once in a year, we were able to obtain an overall saving of €19,152/year.

Conclusions

A very high percentage of subjects maintained a high and safe number of CD4+ cells (>350 cells/μl) during a three-year follow-up. It could be possible to save up to 66% of the costs by reducing the number of CD4+ count determinations in a year, to have other favorable consequences as well, releasing new resources for patient management.

Emulating a trial of joint dynamic strategies: An application to monitoring and treatment of HIV-positive individuals

Decisions about when to start or switch a therapy often depend on the frequency with which individuals are monitored or tested. For example, the optimal time to switch antiretroviral therapy depends on the frequency with which HIV-positive individuals have HIV RNA measured. This paper describes an approach to use observational data for the comparison of joint monitoring and treatment strategies and applies the method to a clinically relevant question in HIV research: when can monitoring frequency be decreased and when should individuals switch from a first-line treatment regimen to a new regimen? We outline the target trial that would compare the dynamic strategies of interest and then describe how to emulate it using data from HIV-positive individuals included in the HIV-CAUSAL Collaboration and the Centers for AIDS Research Network of Integrated Clinical Systems. When, as in our example, few individuals follow the dynamic strategies of interest over long periods of follow-up, we describe how to leverage an additional assumption: no direct effect of monitoring on the outcome of interest. We compare our results with and without the "no direct effect" assumption. We found little differences on survival and AIDS-free survival between strategies where monitoring frequency was decreased at a CD4 threshold of 350 cells/μl compared with 500 cells/μl and where treatment was switched at an HIV-RNA threshold of 1000 copies/ml compared with 200 copies/ml. The "no direct effect" assumption resulted in efficiency improvements for the risk difference estimates ranging from an 7- to 53-fold increase in the effective sample size.

Brief Report: Drop in CD4+ Counts Below 200 Cells/μL After Reaching (or Starting From) Values Higher than 350 Cells/μL in HIV-Infected Patients With Virological Suppression

BACKGROUND

The aim of the study was to quantify the risk of a drop in CD4 counts below 200 cells/μL after reaching values >350 cells/μL on antiretroviral therapy (ART) (or after starting ART with CD4 count >350 cells/μL) in the absence of virological failure.

SETTING

Ambulatory care services, Italy.

METHODS

Prospective cohort study of patients enrolled in the ICONA Foundation Study cohort who started ART with >350 CD4/μL or with ≤350 CD4/μL and reached values >350 cells/μL after virological suppression (VS, defined by 2 consecutive viral loads ≤50 copies/mL). The date of CD4 count >350 was the baseline for the analysis and those with ≥1 viral load and CD4 count after baseline were included. The primary end point was the cumulative risk (estimated using the Kaplan-Meier method) of a CD4 drop below 200 cells/μL over follow-up, which was censored at the date of virological failure (confirmed HIV-RNA >50 copies/mL), death, or last visit.

RESULTS

Six thousand six hundred sixty-three patients were included. A confirmed CD4 drop below 200 cells/μL was never observed over a median follow-up of 45 (Q1: 21, Q3: 89) months, as long as VS was maintained. Upper limits of the 97.5% confidence interval of rates of confirmed CD4 drop below 200 cells/μL were 0.28 and 0.38/1000 person-years of follow-up for patients with ≤350 and >350 CD4 cells/μL at starting ART.

CONCLUSIONS

In patients who started ART in Italy with >350 CD4 cells/μL or reached >350 CD4 cells/μL after VS, the risk of a CD4 drop below 200 cells/μL in those maintaining VS was negligible.

Comparison of dynamic monitoring strategies based on CD4 cell counts in virally suppressed, HIV-positive individuals on combination antiretroviral therapy in high-income countries: a prospective, observational study

BACKGROUND

Clinical guidelines vary with respect to the optimal monitoring frequency of HIV-positive individuals. We compared dynamic monitoring strategies based on time-varying CD4 cell counts in virologically suppressed HIV-positive individuals.

METHODS

In this observational study, we used data from prospective studies of HIV-positive individuals in Europe (France, Greece, the Netherlands, Spain, Switzerland, and the UK) and North and South America (Brazil, Canada, and the USA) in The HIV-CAUSAL Collaboration and The Centers for AIDS Research Network of Integrated Clinical Systems. We compared three monitoring strategies that differ in the threshold used to measure CD4 cell count and HIV RNA viral load every 3-6 months (when below the threshold) or every 9-12 months (when above the threshold). The strategies were defined by the threshold CD4 counts of 200 cells per μL, 350 cells per μL, and 500 cells per μL. Using inverse probability weighting to adjust for baseline and time-varying confounders, we estimated hazard ratios (HRs) of death and of AIDS-defining illness or death, risk ratios of virological failure, and mean differences in CD4 cell count.

FINDINGS

47 635 individuals initiated an antiretroviral therapy regimen between Jan 1, 2000, and Jan 9, 2015, and met the eligibility criteria for inclusion in our study. During follow-up, CD4 cell count was measured on average every 4·0 months and viral load every 3·8 months. 464 individuals died (107 in threshold 200 strategy, 157 in threshold 350, and 200 in threshold 500) and 1091 had AIDS-defining illnesses or died (267 in threshold 200 strategy, 365 in threshold 350, and 459 in threshold 500). Compared with threshold 500, the mortality HR was 1·05 (95% CI 0·86-1·29) for threshold 200 and 1·02 (0·91·1·14) for threshold 350. Corresponding estimates for death or AIDS-defining illness were 1·08 (0·95-1·22) for threshold 200 and 1·03 (0·96-1·12) for threshold 350. Compared with threshold 500, the 24 month risk ratios of virological failure (viral load more than 200 copies per mL) were 2·01 (1·17-3·43) for threshold 200 and 1·24 (0·89-1·73) for threshold 350, and 24 month mean CD4 cell count differences were 0·4 (-25·5 to 26·3) cells per μL for threshold 200 and -3·5 (-16·0 to 8·9) cells per μL for threshold 350.

INTERPRETATION

Decreasing monitoring to annually when CD4 count is higher than 200 cells per μL compared with higher than 500 cells per μL does not worsen the short-term clinical and immunological outcomes of virally suppressed HIV-positive individuals. However, more frequent virological monitoring might be necessary to reduce the risk of virological failure. Further follow-up studies are needed to establish the long-term safety of these strategies.

FUNDING

National Institutes of Health.