The challenges of determining noninferiority margins: a case study of noninferiority randomized controlled trials of novel oral anticoagulants

Comparison of BMI changes in Japanese adults receiving face-to-face versus online counseling for specific health guidance: a noninferiority prospective observational study

OBJECTIVES

This study aimed to evaluate the noninferiority of online counseling over face-to-face counseling for specific health guidance (SHG).

METHODS

This prospective observational study was conducted using specific health checkup (SHC) and SHG data of individuals with health insurance in Japan. We analyzed data from 1431 participants who met the inclusion criteria, including those who underwent online or face-to-face counseling between April 1, 2020 and March 31, 2021, and received an SHC in the following year but no earlier than 90 days after their first counseling session. Assessed variables comprised demographics, counseling methods, and SHC results, including baseline questionnaire findings and body mass index (BMI) at follow-up. We performed inverse probability of treatment weighting (IPTW) using propensity scores, with changes in BMI as the objective variable and the counseling method as the explanatory variable. We set the noninferiority margin to 0.175, based on a previous study.

RESULTS

The online and face-to-face counseling groups comprised 455 (31.8%) and 976 (68.2%) participants, respectively. The number of men and mean age were 214 (47.0%) and 49.9 years (SD: 6.9 years), respectively, in the online counseling group, and 491 (50.3%) and 51.1 years (SD: 7.6 years), respectively, in the face-to-face counseling group. IPTW using propensity scores revealed a regression coefficient of -0.014 (95% CI: -0.157 to 0.129) for the online group compared with the face-to-face group (P = .847). The CI was within the noninferiority margin.

CONCLUSIONS

The effects of online counseling on BMI are likely noninferior to those of face-to-face counseling.

Best medical management versus intravenous thrombolysis for mild non-disabling ischemic stroke: A prospective noninferiority registry study

OBJECTIVES

The efficacy and safety of intravenous thrombolysis uncertain in patients with non-disabling mild ischemic stroke. Our aim was to investigate whether best medical management only is noninferior to intravenous thrombolysis plus best medical management therapy for achieving favorable functional outcome at 90 days.

MATERIALS AND METHODS

In a prospective acute ischemic stroke registry from 2018 through 2020, 314 non-disabling mild ischemic stroke patients received best medical management only and 638 underwent intravenous thrombolysis plus best medical management. The primary outcome was modified Rankin Scale ≤1 at Day 90. The noninferiority margin was -5%. Secondary outcomes of hemorrhagic transformation, early neurologic deterioration and mortality were also evaluated.

RESULTS

The best medical management only was noninferior to the combined therapy of intravenous thrombolysis and best medical management with regard to the primary outcome (unadjusted risk difference, 1.16%; 95% CI, -3.48% ∼ 5.8%; p = 0.0046 for noninferiority; adjusted risk difference, 3.01%; 95% CI, -3.39% ∼ 9.41%). After propensity score matching, p < 0.0001 for noninferiority. RD, 4.03%; 95% CI, -1.59% ∼ 9.69%. p < 0.0001 for noninferiority. Adjusted RD, 5.23%; 95% CI, -1.88% ∼ 9.97%. The occurrence of hemorrhagic transformation was significantly increased in the group of combination therapy (OR, 4.26; 95% CI, 1.30 to 13.99; p = 0.008), while no significant difference was detected in early neurologic deterioration (OR, 1.11; 95% CI, 0.49-2.52; p = 0.808) and mortality (OR, 0.57; 95% CI, 0.20 to 1.69; p = 0.214) between groups.

CONCLUSIONS

In the present study, we found the best medical management only was noninferior to the combination therapy of intravenous thrombolysis plus best medical management for non-disabling mild ischemic stroke within 4.5 h after onset. Best medical management may be a treatment of choice for non-disabling mild ischemic stroke patients. Further randomized controlled studies are warranted.

Protocol for a Randomized Control Trial for Tungiasis Treatment in Homa Bay County, Kenya: Dimeticone versus Sodium Carbonate

Tungiasis, a World Health Organization neglected tropical disease, is caused by the female sand flea. Most clinical trials for tungiasis use expensive or impractical drugs, which are difficult for residents to use. However, in western Kenya, communities successfully treat tungiasis with sodium carbonate. We hypothesise that the topical risk-difference of 5% sodium carbonate is no more than 10% non-inferior to dimeticone (NYDA^®) for tungiasis treatment. This is a protocol for a non-inferiority study, which will be randomised and with an observer-blinded control. The study will have two arms: 5% sodium carbonate and NYDA^®, one on each foot, and will take place at state primary schools in Homa Bay County, Kenya. Fleas identified among school children aged 8-14 years with sand-flea lesions will be enrolled in the study. For each participant, the viability of the embedded fleas, clinical signs including inflammation, and symptoms will be monitored for seven days after treatment. The proportion of dead fleas will be compared in the primary analysis. All adverse events will be monitored throughout the study period. We expect to identify the most effective treatment between sodium carbonate and NYDA^® for tungiasis, which can be adopted in the community.

Inconsistencies in the Methodological Framework Throughout Published Studies in High-Impact Orthopaedic Journals: A Systematic Review

BACKGROUND

Both the Standard Protocol Items: Recommendations for Interventional Trials (SPIRIT) and Consolidated Standards of Reporting Trials (CONSORT) guidelines recommend that clinical trials follow a study framework that aligns with their objective to test the relative efficacy or safety (equality) or effectiveness (superiority, noninferiority, or equivalence) between interventions. We conducted a systematic review to assess the proportion of studies that demonstrated inconsistency between the framing of their research question, sample size calculation, and conclusion and those that should have framed their research question differently based on the compared interventions.

METHODS

We included studies from 5 high-impact-factor orthopaedic journals published in 2017 and 2019 that compared at least 2 interventions using patient-reported outcome measures.

RESULTS

We included 228 studies. The sample size calculation was reported in 60.5% (n = 138) of studies. Of these, 52.2% (n = 72) were inconsistent between the framing of their research question, sample size calculation, and conclusion. The majority (n = 137) of sample size calculations were for equality, but 43.8% of these studies concluded superiority, noninferiority, or equivalence. Studies that framed their research question as equality (n = 186) should have been framed as superiority (n = 129), equivalence (n = 52), or noninferiority (n = 3). Only 2 studies correctly framed their research question as equality.

CONCLUSIONS

Studies published in high-impact journals were inconsistent between the framing of their research question, sample size calculation, and conclusion. Authors may be misinterpreting research findings and making clinical recommendations solely based on p values. Researchers are encouraged to state and justify their methodological framework and choice of margin(s) in a publicly published protocol as they have implications for sample size and the applicability of conclusions.

CLINICAL RELEVANCE

The results of clinical research must be interpreted using confidence intervals, with careful consideration as to how the confidence intervals relate to clinically meaningful differences in outcomes between treatments. The more typical practice of relying on p values leaves the clinician at high risk of erroneous interpretation, recommendation, and/or action.

The evaluation of noninferiority for renal composite outcomes between sodium-glucose cotransporter inhibitors in Japan

BACKGROUND

In Japan, six types of sodium-glucose cotransporter inhibitors (SGLT2Is) are currently in use. Here, we evaluated differences in renal composite outcomes between SGLT2Is with or without evidence of cardio vascular outcome trials (CVOTs).

METHODS

We retrospectively surveyed 536 Japanese patients with type 2 diabetes mellitus with chronic kidney disease who received SGLT2Is for more than 1 year. Patients were classified as having received empagliflozin, canagliflozin, or dapagliflozin (n = 270, Evidence (+) group) or as having received ipragliflozin, tofogliflozin, or luseogliflozin (n = 266, Evidence (-) group). The propensity score matching method was performed.

RESULT

On matched cohort model including 205 cases in each group, there were no significant differences in the incidence of renal composite outcomes (n = 28 [14%] in the Evidence (+) group, n = 21 [10%] in the Evidence (-) group for the matched model; p = 0.29) between groups. Cox hazard analyses in the matched cohort model showed that the risk ratio for renal composite outcomes in the Evidence (-) group was 0.73 (95% confidence interval: 0.40-1.32), which was greater than the noninferiority margin of 1.22.

CONCLUSION

Three SGLT2Is with no CVOT's evidence did not show noninferiority compared with other SGLT2Is with evidences.

The Effectiveness of Intranasal Midazolam for the Treatment of Prehospital Pediatric Seizures: A Non-inferiority Study

Background: Intranasal (IN) midazolam allows for rapid, painless treatment of pediatric seizures in the prehospital setting and may be a preferred administration route if determined to be non-inferior to intravenous (IV) or intramuscular (IM) routes. We sought to evaluate the effectiveness of IN midazolam for terminating prehospital pediatric seizures compared to midazolam administered by alternate routes. Methods: We performed a retrospective, non-inferiority analysis using data from a regional Emergency Medical Services (EMS) database. We included pediatric patients ≤ 14 years treated with midazolam (0.1 mg/kg) by EMS for non-traumatic seizures. The primary outcome was the proportion of patients requiring redosing of midazolam after initial treatment with IN midazolam compared to those that received IV or IM midazolam. We established a priori a risk difference of 6.5% as the non-inferiority margin. Results: We evaluated outcomes from 2,034 patients (median age 6 years [interquartile range 3 - 10 years], 55% male). Initial administration routes were 461 (23%) IN, 547 (27%) IM, 1024 (50%) IV, and 2 (0.1%) intraosseous (IO). Midazolam redosing occurred in 116 patients (25%) who received IN midazolam versus 222 patients (14%) treated initially with midazolam via alternate routes (risk difference 11% [95%CI 7 - 15%]). The age-adjusted odds ratio for redosing midazolam after intranasal administration compared to alternate route administration was 2.0 (95% CI 1.6 - 2.6). Conclusion: Prehospital treatment of pediatric seizure with intranasal midazolam was associated with increased frequency of redosing compared to midazolam administered by other routes, suggesting that 0.1 mg/kg is a subtherapeutic dose for intranasal midazolam administration.

A note on the determination of non-inferiority margins with application in oncology clinical trials

The goal of a non-inferiority trial is to evaluate whether the effect of an experimental treatment is not inferior to that of the active control. Determination of an appropriate non-inferiority margin is critical to the demonstration of non-inferiority. A commonly used method is called the fixed-margin approach recommended by the FDA. The fixed-margin approach consists of two steps: first the lower limit of the 1 - α * two-sided confidence interval (CI) of the active-control effect versus placebo is calculated from relevant historical trials or meta-analysis; second, the non-inferiority margin is obtained as a fraction of the lower confidence limit of the control effect to preserve partial control effect. An alternative method is to use the point estimate, instead of the lower confidence limit, of the active-control effect. The fixed-margin approach based on the lower limit may be ultra-conservative with unconditional Type 1 error rate much smaller than target α / 2 level, while the margin based on the point estimate is liberal. We derive the Type 1 error rate as a function of variances of the effect estimates in the historical and the current non-inferiority trials. We also propose an alternative approach for the non-inferiority margin that maintains the target Type 1 error rate. For the endpoint of landmark survival, we conduct simulations to compare the fixed-margin methods and the proposed method. For illustration, we apply the proposed method to an oncology non-inferiority clinical trial to determine an alternative non-inferiority margin.

A Non-inferiority Framework for Cost-Effectiveness Analysis

BACKGROUND

Traditional decision rules have limitations when a new technology is less effective and less costly than a comparator. We propose a new probabilistic decision framework to examine non-inferiority in effectiveness and net monetary benefit (NMB) simultaneously. We illustrate this framework using the example of repetitive transcranial magnetic stimulation (rTMS) and electroconvulsive therapy (ECT) for treatment-resistant depression.

METHODS

We modeled the quality-adjusted life-years (QALYs) associated with the new intervention (rTMS), an active control (ECT), and a placebo control, and we estimated the fraction of effectiveness preserved by the new intervention through probabilistic sensitivity analysis (PSA). We then assessed the probability of cost-effectiveness using a traditional cost-effectiveness acceptability curve (CEAC) and our new decision-making framework. In our new framework, we considered the new intervention cost-effective in each simulation of the PSA if it preserved at least 75 percent of the effectiveness of the active control (thus demonstrating non-inferiority) and had a positive NMB at a given willingness-to-pay threshold (WTP).

RESULTS

rTMS was less effective (i.e., associated with fewer QALYs) and less costly than ECT. The traditional CEAC approach showed that the probabilities of rTMS being cost-effective were 100 percent, 39 percent, and 14 percent at WTPs of $0, $50,000, and $100,000 per QALY gained, respectively. In the new decision framework, the probabilities of rTMS being cost-effective were reduced to 23 percent, 21 percent, and 13 percent at WTPs of $0, $50,000, and $100,000 per QALY, respectively.

CONCLUSIONS

This new framework provides a different perspective for decision making with considerations of both non-inferiority and WTP thresholds.

Bayesian Approach for Assessing Non-inferiority in Three-arm Trials for Risk Ratio and Odds Ratio

In this paper we consider three-arm non-inferiority (NI) trial that includes an experimental, a reference, and a placebo arm. While for binary outcomes the risk difference (RD) is the most common and well explored functional form for testing efficacy (or effectiveness), recent FDA guideline suggested other measures such as relative risk (RR) and odds ratio (OR) on the basis of which NI of an experimental treatment can be claimed. However, developing test based on these different functions of binary outcomes are challenging since the construction and interpretation of NI margin for such functions are not trivial extensions of RD based approach. Recently, we have proposed Frequentist approaches for testing NI for these functionals. In this article we further develop Bayesian approaches for testing NI based on effect retention approach for RR and OR. Bayesian paradigm provides a natural path to integrate historical trials' information, as well as it allows the usage of patients'/clinicians' opinions as prior information via sequential learning. In addition we discuss, in detail, the sample size/power calculation which could be readily used while designing such trials in practice.

Approaches for testing noninferiority in two-arm trials for risk ratio and odds ratio

For an existing established drug regimen, active control trials are defacto standard due to ethical reason as well as for clinical equipoise. However, when superiority claim of a new drug against the active control is unlikely to be successful, researchers often address the issue in terms of noninferiority (NI), provided the experimental drug demonstrates the evidence of other benefits beyond efficacy. Such trials aim to demonstrate that an experimental treatment is non-inferior to an existing comparator by not more than a pre-specified margin. The issue of choosing such a margin is complex. In this article, two-arm NI trials with binary outcomes are considered when margin is defined in terms of relative risk or odds ratio. A Frequentist test based on proposed NI margin is developed first. Since two-arm NI trials without placebo arm are dependent upon historical information, in order to make accurate and meaningful interpretation of their results, a Bayesian approach is developed next. Bayesian approach is flexible to incorporate the available information from the historical trial. The operating characteristics of the proposed methods are studied in terms of power and sample size for varying design factors. A clinical trial data is reanalyzed to study the properties of the proposed approach.

A Local Sensitivity Analysis of the Trial of Continuous or Interrupted Chest Compressions during Cardiopulmonary Resuscitation: Is a Local Protocol Change Required?

Objective

The “Trial of Continuous (CCC) or Interrupted Chest Compressions (ICC) during Cardiopulmonary Resuscitation (CPR)” compared two CPR strategies for out-of-hospital cardiac arrest (OHCA). Although results were neutral, there was suggestion of benefit for ICC. However, nearly 50% of study patients had a protocol violation; regional variations may have played a role in protocol adherence and outcomes. We analyzed our British Colombia (BC) cohort to decide whether a protocol change from CCC to ICC was justified.

Methods

This was a post-hoc analysis of BC-enrolled study patients. The primary between-group comparison was favorable neurological outcome (modified Rankin scale ≤ 3) using intention-to-treat. Secondary analyses compared those treated per-protocol (adjusted) and the top compliant clusters (unadjusted). We classified protocol violations using a structured algorithm. We used logistic regression and computed the difference in probabilities using the marginal standardization method with bootstrapping to calculate confidence intervals.

Results

There were 3769 patients included, with a median age of 69 years (IQR: 56–80). There were protocol violations in 3.2% of those in the CCC group and 27% of those in the ICC group. In patients randomized to CCC or ICC, 11.2% and 10.8% (risk difference 0.42%; 95% CI -1.58, 2.41) had favorable neurological outcomes, respectively. In the per-protocol and top compliant clusters comparisons, risk differences were 0.25% (95% CI -1.70, 2.25) and 2.95% (95% CI -0.68, 6.58).

Conclusion

Our comparisons suggest that CCC may be the preferred strategy in our region and is likely not resulting in worse outcomes. Based on the original study and our local analysis, we found no compelling reasons to change our local strategy from CCC to ICC.

Non-inferiority Testing for Risk Ratio, Odds Ratio and Number Needed to Treat in Three-arm Trial

Three-arm non-inferiority (NI) trial including the experimental treatment, an active reference treatment, and a placebo where the outcome of interest is binary are considered. While the risk difference (RD) is the most common and well explored functional form for testing efficacy (or effectiveness), however, recent FDA guideline suggested measures such as relative risk (RR), odds ratio (OR), number needed to treat (NNT) among others, on the basis of which NI can be claimed for binary outcome. Albeit, developing test based on these different functions of binary outcome are challenging. This is because the construction and interpretation of NI margin for such functions are non-trivial extensions of RD based approach. A Frequentist test based on traditional fraction margin approach for RR, OR and NNT are proposed first. Furthermore a conditional testing approach is developed by incorporating assay sensitivity (AS) condition directly into NI testing. A detailed discussion of sample size/power calculation are also put forward which could be readily used while designing such trials in practice. A clinical trial data is reanalyzed to demonstrate the presented approach.

Some issues for the evaluation of noninferiority trials

Although published noninferiority trials (NITs) generally conclude that the experimental intervention being studied is noninferior compared with standard therapy or active control, NIT quality is often not satisfactory. We have proposed 14 questions to assist in evaluating the clinical evidence of the experimental versus standard therapy. The aim of these questions is to critically appraise NITs and support proper interpretation of study results. Readers should not only consider whether the confidence interval of the primary effect measure falls within the prespecified noninferiority margin (thus concluding noninferiority), but also assess the similarities between primary and secondary outcomes for the experimental and standard therapy. To conclude noninferiority conceptually is to synthesize evidence from both the current NIT comparing experimental therapy with standard therapy and historical data comparing standard therapy with placebo control. Therefore, readers should use external data sources (e.g., historical data) to validate the study design (e.g., selection of standard therapy, effect measure and the noninferiority margin), and assess the uncertainty of findings due to differences between the observed and expected incidence rates, follow-up time, effects of adjuvant therapy and the secondary outcomes of therapies. Following an explanation of the 14 questions, we then apply the questions to a NIT on intraoperative radiation therapy for early stage breast cancer, as an example.

Design of non-inferiority randomized trials using the difference in restricted mean survival times

Background/aims Non-inferiority trials with time-to-event outcomes are becoming increasingly common. Designing non-inferiority trials is challenging, in particular, they require very large sample sizes. We hypothesized that the difference in restricted mean survival time, an alternative to the hazard ratio, could lead to smaller required sample sizes. Methods We show how to convert a margin for the hazard ratio into a margin for the difference in restricted mean survival time and how to calculate the required sample size under a Weibull survival distribution. We systematically selected non-inferiority trials published between 2013 and 2016 in seven major journals. Based on the protocol and article of each trial, we determined the clinically relevant time horizon of interest. We reconstructed individual patient data for the primary outcome and fit a Weibull distribution to the comparator arm. We converted the margin for the hazard ratio into the margin for the difference in restricted mean survival time. We tested for non-inferiority using the difference in restricted mean survival time and hazard ratio. We determined the required sample size based on both measures, using the type I error risk and power from the original trial design. Results We included 35 trials. We found evidence of non-proportional hazards in five (14%) trials. The hazard ratio and the difference in restricted mean survival time were consistent regarding non-inferiority testing, except in one trial where the difference in restricted mean survival time led to evidence of non-inferiority while the hazard ratio did not. The median hazard ratio margin was 1.43 (Q1-Q3, 1.29-1.75). The median of the corresponding margins for the difference in restricted mean survival time was -21 days (Q1-Q3, -36 to -8) for a median time horizon of 2.0 years (Q1-Q3, 1-3 years). The required sample size according to the difference in restricted mean survival time was smaller in 71% of trials, with a median relative decrease of 8.5% (Q1-Q3, 0.4%-38.0%). Across all 35 trials, about 25,000 participants would have been spared from enrollment using the difference in restricted mean survival time compared to hazard ratio for trial design. Conclusion The margins for the hazard ratio may seem large but translate to relatively small differences in restricted mean survival time. The difference in restricted mean survival time offers meaningful interpretation and can result in considerable reductions in sample size. Restricted mean survival time-based measures should be considered more widely in the design and analysis of non-inferiority trials with time-to-event outcomes.

The Impact of the Underlying Risk in Control Group and Effect Measures in Non-Inferiority Trials With Time-to-Event Data: A Simulation Study

Background

We designed a simulation study to assess how the conclusions of a non-inferiority trial (NIT) will change if the observed risk is different from the expected risk.

Methods

We simulated Weibull distribution time-to-event data with a true hazard ratio (HR) being equal or close to 1. The empirical margins and sample size of a hypothetical trial were chosen based on a systematic review. Setting the significance level at 5% for the two-sided confidence interval (CI), we examined the statistical power (i.e., the probabilities of the upper limit of the 95% CI falling within the margin) of using two measures at various underlying risk in the control group.

Results

Using the empirical margins, HRs of 1.2, 1.35 or 1.5, the statistical power is lower than 0.22 when the underlying risk in the control group is less than 10%, but the power increases along with the higher underlying risk. The predicted upper limit of the 95% CI of the difference in two Kaplan-Meier estimators (DTKME) is low when risk is low (< 20%) or high (> 80%), but reaches the highest value when risk is around 50%. When the underlying risk in the control group is lower than 10%, measures of DTKME resulted in much higher power than HR.

Conclusions

When HR is the effect measure, the probability of concluding non-inferiority will increase as the underlying risk in the control group increases. When DTKME is the effect measure, the probability of concluding non-inferiority will decrease as the underlying risk in the control increases. In this case, the probability of concluding non-inferiority is at a minimum when the control risk reaches about 50%. When the risk in the control arm is less than 10%, the conclusion of an NIT is sensitive to the choice of effect measure.

Defining the noninferiority margin and analysing noninferiority: An overview

Noninferiority trials are used to assess whether the effect of a new drug is not worse than an active comparator by more than a noninferiority margin. If the difference between the new drug and the active comparator does not exceed this prespecified margin, noninferiority can be concluded. This margin must be specified based on clinical and statistical reasoning; however, it is considered as one of the most challenging steps in the design of noninferiority trials. Regulators recommend that the margin should be defined based on the historical evidence of the active comparator (the latter is often the well-established standard treatment of the disease), which can be performed by different approaches. There are several factors and assumptions that need to be accounted for during the process of defining the margin and during the analysis of noninferiority. Three methods are commonly used to analyse noninferiority trials: the fixed-margin method; the point-estimate method; and the synthesis method. This article provides an overview of analysing noninferiority and choosing the noninferiority margin.

Sample Size for Biosimilar Trials: In Defense of Synthesis

Biosimilars are biological products similar to, but not the same as, the innovator products. Both the European Medicines Agency and the Food and Drug Administration have released detailed guidance on the development of biosimilars. This guidance requires the pivotal phase 3 clinical study to have an equivalence design, which means that the study objective is to demonstrate that one treatment is neither "worse than" nor "better than" the other by some "clinically unimportant" amount. The most critical and controversial step in designing such a study is the choice of equivalence margin, as this determines the conclusion of the study. In this paper, we outline the methodology for determining an equivalence margin and, through case studies on biosimilar trastuzumab (HERCEPTIN ) and biosimilar bevacizumab (AVASTIN), explain the challenges of applying this in practice and why the synthesis method should be given greater consideration by regulatory authorities and biosimilar developers.

Choice of non-inferiority (NI) margins does not protect against degradation of treatment effects on an average--an observational study of registered and published NI trials

OBJECTIVE

NI margins have to be chosen appropriately to control the risk of degradation of treatment effects in non-inferiority (NI) trials. We aimed to study whether the current choice of NI margins protects sufficiently against a degradation of treatment effect on an average.

STUDY DESIGN AND SETTING

NI trials reflecting current practice were assembled and for each trial, the NI margin was translated into a likelihood of degradation. The likelihood of degradation was calculated as the conditional probability of a treatment being harmful given that it is declared non-inferior in the trial, using simulation. Its distribution among the NI trials was then studied to assess the potential risk of degradation.

RESULTS

The median (lower/upper quartile) NI margin among 112 binary outcome NI trials corresponded to an odds ratio of 0.57(0.45, 0.66), while among 38 NI trials with continuous outcome, to a Cohen's d of -0.42(-0.54, -0.31) and a hazard ratio of 0.82(0.73, 0.86) among 24 survival outcome NI trials. Overall, the median likelihood of degradation was 56% (45%, 62%).

CONCLUSION

Only two fifths of the current NI trials had a likelihood of degradation lower than 50%, suggesting that, in majority of the NI trials, there is no sufficient protection against degradation on an average. We suggest a third hurdle for the choice of NI margins, thus contributing a sufficient degree of protection.

A clinician's guide to the assessment and interpretation of noninferiority trials for novel therapies

A noninferiority trial is designed to demonstrate that an experimental therapy is not worse than an active control. Although noninferiority trials are superficially similar to conventional superiority trials, there are fundamental differences. In particular, aspects of a study that make the therapies appear more similar than they actually are can falsely bias the study toward demonstrating noninferiority. This has important implications for methodologic techniques such as blinding and statistical analysis based on the intention-to-treat principle. When applying the results of noninferiority trials, clinicians should be judicious in determining whether the degree of noninferiority demonstrated is clinically acceptable and whether the ancillary benefits of the treatment justify its use.