[06.11] Quantitative Study Designs_ Experimental Study Designs V2.pdf

Analytic and experimental study design

Under what category of epidemiological study design strategies do Randomized Controlled Trials (RCTs) fall?

Intervention

What does an analytic and experimental study design involve?

To see how a particular intervention affects a certain outcome

What is the purpose of RCTs?

Selection of a sample from the population, Measurement of the variables (characteristics) at baseline, To randomize, To apply the intervention (one should be blinded, placebo), Follow up the cohorts, Measure outcome variables (blindly, if possible)

What are the six elements of basic RCT design?

After the measurement of baseline characteristics

When does randomization happen in the basic RCT design?

Interventions will be applied and groups will be randomized

What is the difference between an RCT and a cohort study?

Measure the outcome of interest (blindly, if possible)

What is the most important thing after following up the cohorts in an RCT?

Randomized Blinded Trial (RBT)

What type of trial is used to assess the efficacy of a treatment in preventing a disease?

Avoids systematic differences between groups with respect to known or unknown baseline variables that could affect the outcome, Minimizes bias, Provides a sound basis for statistical inference

What are the three functions or purposes of the randomization process?

To allow discrimination of patient outcomes

What is the major purpose of the control group?

Changes in symptoms, signs, or other morbidity caused by the test treatment

What specific outcomes does the control group help discriminate from outcomes based on other factors?

Natural progression of the disease, observer or patient expectations, or other treatment

What are examples of 'other factors' whose outcomes the control group helps discriminate against?

Type of treatment used, The method of determining who will be in the control group

What two bases are used to classify control groups in RCTs?

Placebo, No treatment, Different dose or regimen of the study treatment, Different active treatment

What are the four types of control treatments for RCTs?

Due to ethical considerations

Why is the 'no treatment' control group usually not used anymore?

Overall survival rate

What is a possible endpoint of interest, especially for cancer drugs?

Progression-free survival

What possible endpoint is important in assessing metastasis or recurrence of cancer among interventions?

Time to progression

What possible endpoint measures how long the disease takes to progress again, or recurrence rate, from the time the drug is given?

Response rate (CR + PR)

What possible endpoint is compared, based on complete response and partial response?

Disease control rate (CR + PR + SD)

What possible endpoint is compared, based on complete response, partial response, and stable disease?

Phase IV of clinical trials and post-market surveillance

When is the safety profile usually evaluated?

Post-market surveillance

What is the term for the period when drugs are still under control trials and adverse effects are reported?

Tumor markers collected prior to therapy

What is assessed and correlated with treatment outcome, particularly in cancer studies?

Survival rates

What are most RCTs initially conducted for?

Superiority trial, Equivalence trial, Non-inferiority trial

What are the three types of RCTs discussed?

Superiority trial

What type of trial is designed to detect a difference between two treatments (e.g., Is Drug A better than Drug B)?

Test of statistical significance

What is the usual first step in the analysis of a superiority trial?

Whether the results of the trial are consistent with the assumption of there being no difference in the clinical effects of the two treatments

What does the test of statistical significance determine in a superiority trial?

Point and interval estimates of the difference between the two treatments

What is computed when the results of the initial test of hypothesis in a superiority trial is 'significant'?

Relative risk for proportions

What can also be used in superiority trials because the goal is to find out the difference?

95%

What is the common confidence interval used in statistical analysis?

0.05

What is the common alpha ($\alpha$) level used in statistical analysis?

Significant

What does a p-value less than $\alpha$ (0.05) indicate?

Superiority is shown more strongly in Drug A than Drug B

In a superiority trial (Figure 4), what does a p-value of less than 0.002 suggest as compared to a p-value of 0.05?

Liraglutide (Saxenda)

What is a classical example of a GLP-1 inhibitor discussed in the context of a superiority trial involving a placebo?

Diabetes

For which patients were GLP-1 inhibitors initially used?

Lost a lot of weight

What unexpected observation led to the approval of Liraglutide for obesity?

No weight was regained

What positive finding was observed among obese patients given Liraglutide at the therapeutic dose over 12 months?

Nausea, vomiting, and decreased gastric emptying time

What were the three adverse events of Liraglutide observed in the study?

Stop GLP-1 inhibitors for at least 1 week prior to an operation

What observation by anesthesiologists led to a change in clinical practice due to decreased gastric emptying time?

Semaglutide

What is another famous GLP-1 inhibitor mentioned?

Equivalence trial

What type of trial is designed to confirm the absence of a meaningful difference between treatments (e.g., Is Drug A equally effective as Drug B)?

Drug manufacturers

Who usually uses equivalence trials to prove the efficacy of a new drug compared to a market gold standard drug?

Margin of clinical equivalence ($\Delta$)

What concept, defined as the largest clinically acceptable difference, is used in equivalence trials?

The new agent is better

In an equivalence trial (Figure 5), what is suggested if the difference exceeds $+\Delta$ (upper margin of equivalence)?

The control drug is better

In an equivalence trial (Figure 5), what is suggested if the difference exceeds $-\Delta$ (lower margin of equivalence)?

The equivalence of the two drugs

What is shown if the results stay within the margin of clinical equivalence?

Modified release products or topical preparations

Give an example of areas where bioequivalence studies are not possible but where essential similarity needs to be demonstrated (making superiority/equivalence trials irrelevant).

Diseases for which the use of a placebo is not possible to demonstrate the efficacy of the test product

What specific scenario related to placebo use makes superiority or equivalence trials irrelevant/unuseful?

Non-inferiority trial

What type of trial is designed to show that a new treatment is no less effective than an existing treatment (e.g., Is Drug A the same or no worse off than Drug B)?

Non-inferiority is shown

In a non-inferiority trial (Figure 6), what is indicated when the margin of clinical safety (or equivalence) is not breached and shifts to the right?

Non-inferiority is NOT shown

In a non-inferiority trial (Figure 6), what is indicated when the treatment goes past the margin of clinical efficacy (or equivalence)?

Statistical reasoning and clinical judgment

What two factors determine the selection of the non-inferiority margin?

A 3-armed trial with a test, reference, and placebo

What type of trial will allow some within-trial validation of the choice of the non-inferiority margin?

The test drug has a clinically relevant effect greater than zero

What assurance must the non-inferiority margin provide regarding the test drug?

Bioequivalence

For what concept are non-inferiority trials usually done?

Determine if a generic drug is non-inferior to the innovator drug

What is the specific purpose of a non-inferiority study related to generic drugs?

Zithromax

What innovator drug example was used to explain bioequivalence and generic drugs?

Botox

What classical example of RCTs where treatment cannot be given (aesthetic medicine) was used to explain non-inferiority trials?

Xeomin and Dysport

What two other toxins were mentioned in the non-inferiority trial example related to Botox?

Influenza A

What specific example of a vaccine was used to illustrate non-inferiority trials related to innovator brands losing patents?

Statistical methods to be performed, Interim analysis to be performed, Number of subjects per center for multicenter trials, Levels of significance to be used, Criteria for termination of trials or exit of patients in the trials, Procedures for dealing with missing, unused, or spurious data, Procedures for deviation from protocol

What seven considerations are involved in statistical procedures and analysis of RCTs?

Cohort study

What type of study is an RCT also considered, which runs over certain periods of time, requiring interim analysis?

Discovered that the drug initially invented for patients with diabetes had an effect (significant weight loss) on obese diabetic patients

What discovery was made during the interim analysis report for Liraglutide (Saxenda)?

Minoxidil

What drug, known for hair restoration, was initially given to patients with hypertension?

Latisse (Bimatoprost)

What drug, initially used for glaucoma patients, was noticed to cause longer eyelashes in an interim study?

Generalizability of the results, Include the patient population in different settings

What are the two purposes of having multicenter trials or multi-country studies?

Investigate why the patient deviated from protocol, Did the patient have any adverse events, Were these adverse events given intervention, Were the patients eventually allowed to continue with the protocol

What are the four considerations researchers must investigate regarding deviations from the protocol?

Intention-to-treat data set, Full analysis data set, Per protocol data set

What are the three different data sets available for analysis?

No protocol violations, perfect subject compliance, no drop-outs, no missing data

What four characteristics define the 'Trialist’s Dream'?

Intention-to-treat analysis (ITT)

What principle asserts that the effect of a treatment policy should be assessed based on the planned treatment regimen, regardless of the actual treatment given or compliance?

Followed up, assessed and analyzed as members of that group

In ITT analysis, subjects allocated to a treatment group must be treated this way, irrespective of their compliance to the planned course of treatment.

Full analysis set

What set of subjects is defined as being as close as possible to the ideal implied by the intention-to-treat principle?

Failure to satisfy major entry criteria (eligibility violations), Failure to take at least one dose of trial medication, Lack of any data post-randomization

What are three reasons why randomized subjects might be excluded from the full analysis set?

Per protocol set

What set of data is generated by the subset of subjects who complied with the protocol sufficiently to ensure that the data would be likely to exhibit the effects of treatment?

Valid cases, Efficacy samples, Evaluable subjects sample

What are the three alternative terms for the per protocol set?

Exposure to treatment, Availability of measurements, Absence of protocol violations

What three considerations does compliance cover in the context of the per protocol set?

To minimize bias, To avoid inflating Type 1 Error (erroneous acceptance of an inferior new treatment)

What are the two guiding principles that should always guide analysis in choosing the appropriate data set?

Erroneous acceptance of an inferior new treatment

What does inflating Type 1 Error mean in the context of guiding principles for analysis?

"The test and reference products differ"

What is the null hypothesis in a non-inferiority trial?

"The test and reference products are equally effective"

What is the alternative hypothesis in a non-inferiority trial?

Intention-to-treat (or at least the full analysis set)

What data set is recommended for a Test of Superiority?

Per protocol data set

What data set is recommended for a Test of Non-Inferiority?

Gold standard

How are RCTs generally viewed among experimental study designs?

Randomization

What is the primary advantage of an RCT over other study designs?

Minimizes the influence of known and unknown confounding variables that may bias the study results

How does randomization function in an RCT?

Blinding

What function preserves the benefits of randomization and prevents bias in the adjudication of the intended outcome?

External validity

What term refers to the goal of creating a sample population that is truly representative of the whole, allowing results to be generalized with confidence?

Phase I

Which clinical trial phase tests an experimental drug in 20-80 people to evaluate safety, determine a safe dosage range, and identify side effects?

Phase II

Which clinical trial phase tests the drug in 100-300 people to determine effectiveness and evaluate safety?

Phase III

Which clinical trial phase tests the drug in 1000-3000 people to confirm effectiveness, monitor side effects, compare it to commonly used treatments, and collect information for safe use?

Phase IV

Which clinical trial phase involves post-marketing studies to learn more about the drug’s risks, benefits, and optimal uses?

Investigating harm

What is a limitation of RCTs that makes them not appropriate for answering clinical questions?

It is unethical to randomize patients to an intervention suspected of having a harmful effect

Why are RCTs not appropriate for investigating harm?

Logistically difficult and expensive

Why do RCTs often fail to adequately explore harmful events that occur at a rate less than 1 in 100 patients?

Minimizing bias

What function does randomization serve in an RCT, according to the summary?

Provides a sound basis for statistical inference

What basis does randomization provide, according to the summary?

Detect a difference between two treatments

What is the design objective of superiority trials?

Confirm the absence of a meaningful difference between treatments

What is the design objective of equivalence trials?

Show that a new treatment is no less effective than an existing treatment

What is the design objective of non-inferiority trials?