Assessing the validity of surrogate endpoints in the context of a controversy about the measurement of effectiveness of hepatitis C virus treatment

The relationship between viral clearance rates and disease progression in early symptomatic COVID-19: a systematic review and meta-regression analysis

BACKGROUND

Effective antiviral drugs accelerate viral clearance in acute COVID-19 infections; the relationship between accelerating viral clearance and reducing severe clinical outcomes is unclear.

METHODS

A systematic review was conducted of randomized controlled trials (RCTs) of antiviral therapies in early symptomatic COVID-19, where viral clearance data were available. Treatment benefit was defined clinically as the relative risk of hospitalization/death during follow-up (≥14 days), and virologically as the SARS-CoV-2 viral clearance rate ratio (VCRR). The VCRR is the ratio of viral clearance rates between the intervention and control arms. The relationship between the clinical and virological treatment effects was assessed by mixed-effects meta-regression.

RESULTS

From 57 potentially eligible RCTs, VCRRs were derived for 44 (52 384 participants); 32 had ≥1 clinical endpoint in each arm. Overall, 9.7% (R2) of the variation in clinical benefit was explained by variation in VCRRs with an estimated linear coefficient of -0.92 (95% CI: -1.99 to 0.13; P = 0.08). However, this estimate was highly sensitive to the inclusion of the recent very large PANORAMIC trial. Omitting this outlier, half the variation in clinical benefit (R2 = 50.4%) was explained by variation in VCRRs [slope -1.47 (95% CI -2.43 to -0.51); P = 0.003], i.e. higher VCRRs were associated with an increased clinical benefit.

CONCLUSION

Methods of determining viral clearance in COVID-19 studies and the relationship to clinical outcomes vary greatly. As prohibitively large sample sizes are now required to show clinical treatment benefit in antiviral therapeutic assessments, viral clearance is a reasonable surrogate endpoint.

Decision-making given surrogate outcomes

BACKGROUND

Opinions differ about the extent to which intervention research should and can directly assess the main patient-important health outcomes, what role surrogate endpoints can play, and which requirements should then apply to the scientific underpinning of clinical and policy decisions.

METHOD

In a commentary we elaborate on this and provide guidance for dealing with related dilemmas.

CONCLUSIONS

Ethical, methodological and practical reasons for decision making based on surrogate endpoints can be that (1) reaching the intended patient-important health outcome would take too long to await direct RCT-based evidence, (2) experimental conditions have limited sustainability over time; and (3) the plausibility of an intervention's clinical efficacy, given the already available evidence regarding surrogate endpoints, goes beyond equipoise. Given an expected increase of interventions with a long term patient-important health outcome perspective, dealing with surrogate endpoints will remain an important challenge. Appropriately dealing with a surrogate endpoint includes (1) the assessment of its predictive value for the intended patient-important outcome, where GRADE guidelines for assessing 'indirectness' and 'causal chain analysis' can be helpful; (2) transparency of (absence of) evidence; (3) adequately updating the 'knowledge mosaic'; (4) weighing different perspectives and values, and (5) monitoring whether adjustments need to be made. The remaining level of uncertainty must be balanced against the urgency of clinical or societal decision making and the disadvantages of postponing this. Criteria for using surrogate endpoints are suggested. Patients, citizens and policy makers can be involved in agreeing upon these criteria.

Aspirin dosage for the prevention of graft occlusion in people undergoing coronary surgery: A systematic review and meta-analysis

Background:

Aspirin is almost always used after coronary artery bypass graft (CABG) surgery; however, it is unclear what optimal dose should be prescribed. In this systematic review, we evaluated the effects of high versus low-dose aspirin in patients after CABG.

Methods:

A comprehensive database search was conducted in several databases from date of inception until February 2018. There were no language restrictions. We included studies that compared different doses of aspirin in patients that had undergone CABG surgery. We included studies that evaluated patient-important outcomes (mortality, cardiovascular events, and gastrointestinal bleeding); and if not reported, we collected data on the surrogate outcome thromboxane B2 (TXB2). We collected relevant data and performed a meta-analysis.

Results:

We identified 5903 references, and after two levels of screening by two independent reviewers, we included three randomized controlled trials in the meta-analysis with a total number of 122 participants. Mean age of trial participants was 65.63 years, and 88.68% were male. We planned to analyze all possible clinical outcomes, including mortality, recurrence, and hospitalization. However, no clinical outcomes are reported by the literature. The surrogate biochemical outcome of serum TXB2 was the only outcome reported by the eligible studies. High-dose aspirin (162–325mg once daily) achieved better suppression of TXB2 than low-dose aspirin (75–100mg once daily) (mean difference [MD], 2.00ng/mL, 95% confidence interval [CI]: 0.72–3.32; participants = 122; studies = 3; I² = 0%).

Conclusions:

We found no clinical trials addressing any of the clinical outcomes of interest. High-dose aspirin was superior to low-dose aspirin in suppressing platelet function, a surrogate outcome. Trials evaluating clinical and patient-important outcomes are needed to better inform medical practice and fill this gap in clinical knowledge.

Diagnosis and treatment of lung disease associated with alpha one-antitrypsin deficiency: A position statement from the Thoracic Society of Australia and New Zealand

AATD is a common inherited disorder associated with an increased risk of developing pulmonary emphysema and liver disease. Many people with AATD-associated pulmonary emphysema remain undiagnosed and therefore without access to care and counselling specific to the disease. AAT augmentation therapy is available and consists of i.v. infusions of exogenous AAT protein harvested from pooled blood products. Its clinical efficacy has been the subject of some debate and the use of AAT augmentation therapy was recently permitted by regulators in Australia and New Zealand, although treatment is not presently subsidized by the government in either country. The purpose of this position statement is to review the evidence for diagnosis and treatment of AATD-related lung disease with reference to the Australian and New Zealand population. The clinical efficacy and adverse events of AAT augmentation therapy were evaluated by a systematic review, and the GRADE process was employed to move from evidence to recommendation. Other sections address the wide range of issues to be considered in the care of the individual with AATD-related lung disease: when and how to test for AATD, changing diagnostic techniques, monitoring of progression, disease in heterozygous AATD and pharmacological and non-pharmacological therapy including surgical options for severe disease. Consideration is also given to broader issues in AATD that respiratory healthcare staff may encounter: genetic counselling, patient support groups, monitoring for liver disease and the need to establish national registries for people with AATD in Australia and New Zealand.