Randomized controlled trial
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The randomized controlled trial is considered the most rigorous method for determining whether a causal relationship exists between an intervention and outcome. Participants are randomly assigned to either the experimental group receiving the intervention being tested, or the control group receiving an alternative or placebo treatment. Randomization aims to ensure any differences in outcomes are due to the treatments alone rather than other factors, by making the groups similar in all respects except for the intervention. Common randomization methods include simple, block, and stratified randomization. Blinding of participants and investigators is also important to minimize bias when assessing outcomes.
Randomized controlled trial
- 1. RANDOMIZED CONTROLLED TRIAL DHANADHARANI VENKATESH
- 2. RAMDOMIZED CONTROLLED TRIAL The randomized controlled trial is considered as the most rigorous method of determining whether a cause effective relationship exists between an intervention and outcome The strength of the RTC lies in the process of randomisation that is unique to this type of epidemiological study design Generally, in a randomised controlled trial, study participants are randomly assigned to one of the two groups: The experimental group receiving interventions that is being tested and comparison group (control) which receives a conventional treatment or placebo These groups are then followed prospectively to assess the effectiveness of the intervention compared with standard or placebo treatment
- 3. RANDOMISATION The aim of randomisation is to ensure that any observed difference between the treatment groups are due to difference in the treatment alone and not due to effects of confounding (known or unknown) or trials. That is ,the groups are similar in all respects with the exception of the intervention under investigation Method of random allocation are used to ensure that all study participants have the same chance of allocation to the treatment or control group, and that the likelihood of receiving an intervention is equal regardless of when the participants entered the study. Therefore, the probability of any participant receiving the intervention or the standard treatment / placebo is independent of any other participant being assigned that treatment
- 4. CRITERIA FOR RANDOMIZATION Unpredictability • Each participant has the same chance of receiving any of the interventions. • Allocation is carried out using a chance mechanism so that neither the participant nor the investigator will know in advance which will be assigned. Balance • Treatment groups are of a similar size & constitution, groups are alike in all important aspects and only differ in the intervention each group receives Simplicity • Easy for investigator/staff to implement
- 5. METHOD OF RANDOMISATION Based on allocation of subjects to intervention and control group 1. Simple randomisation 2. Block randomisation 3. Stratified randomisation 4. Unequal randomisation Some other methods such as biased coin, minimization and response- adaptive methods may be applied for specific purposes.
- 6. 1.SIMPLE RANDOMISATION Randomization based on a single sequence of random assignments is known as simple randomization. This technique maintains complete randomness of the assignment of a subject to a particular group. The most common and basic method of simple randomization is flipping a coin. For example, with two treatment groups (control versus treatment), the side of the coin (i.e., heads - control, tails - treatment) determines the assignment of each subject. Other methods include using a shuffled deck of cards (e.g., even - control, odd - treatment) or throwing a dice (e.g., below and equal to 3 - control, over 3 - treatment). A random number table found in a statistics book or computer-generated random numbers can also be used for simple randomization of subjects. This randomization approach is simple and easy to implement in a clinical research. In large clinical research, simple randomization can be trusted to generate similar numbers of subjects among groups. However, randomization results could be problematic in relatively small sample size clinical research, resulting in an unequal number of participants among groups.
- 8. 2.BLOCK RANDOMISATION Block randomisation is a method used to ensure that the numbers of participants assigned to each group is equally distributed and is commonly used in smaller trials.
- 9. 3.STRATIFIED RANDOMISATION Stratified randomisation is used to ensure that important baseline variables (potential confounding factors) are more evenly distributed between groups than chance alone may assure however, there are limited number of baseline variables that can be balanced by stratification because of the potential for small number of subjects within each stratum.
- 10. 4. UNEQUAL RANDOMIZATION Most randomized trials allocate equal numbers of patients to experimental and control groups. This is the most statistically efficient randomization ratio as it maximizes statistical power for a given total sample size. However, this may not be the most economically efficient or ethically/practically feasible. When two or more treatments under evaluation have a cost difference it may be more economically efficient to randomize fewer patients to the expensive treatment and more to the cheaper one. The substantial cost savings can be achieved by adopting a smaller randomization ratio such as a ratio of 2:1, with only a modest loss in statistical power. When one arm of the treatment saves lives and the other such as placebo/medical care only does not much to save them in the oncology trials. The subject survival time depends on which treatment they receive.
- 11. More extreme allocation may be used in these trials to allocate fewer patients into the placebo group. Generally, randomization ratio of 3:1 will lose considerable statistical power, more extreme than 3:1 is not very useful, which leads to much larger sample size
- 12. ADVANTAGE Eliminates confounding tends to create groups that are comparable for all factors that influence outcome, known, unknown or difficult to measure . Therefore, the only difference between the groups should be the intervention Eliminates selection bias Gives validity in statistical tests based on probability theory. This study design can make casual inferences ie, It is the strongest empirical evidence of a treatment efficacy. Randomisation makes groups comparable according both known and unknown factors. Sample size- when adequately powered – avoid both type 1 error ,type 2 error. considered as the “Gold standard” – more published
- 13. DISADVANTAGE Does not guarantee comparable groups are difference in confounding variable may arise by chance. Power calculation might demand vast sample size which require more resources from the investigator. A disadvantage of block randomised is that the allocation of participants may be predictable and results in selection bias when the study groups are considered. Trials which test for efficacy may not be widely applicable trials which test for effectiveness are larger and more expensive. Randomisation requires clinical equipoise: one cannot ethically randomised patients unless both treatments have equal support in the clinical community. Some researcher cannot be ethically performed as an RCT
- 14. BINDING IN RANDOMISED CONTROLLED TRIALS Blinding is a process where the critical information on allocation of treatment is hidden either from the patients, or from observer or the evaluator in the study The method of blinding RCT is used to ensure that there is no difference in the way in which each group is assessed or managed and therefore minimized bias Bias may be introduced . For example, if the investigator is aware of which treatment a subject is receiving as this may influence (intentionally or unintentionally) the way in which outcome data is measured or interpreted. Similarly a subjects knowledge of treatment assignment may influence their response to a specific treatment. Types of blinded study includes- single blinded, double blinded, triple blinded A single blind RCT is when the investigator knows but not the study participants known which treatment has been allocated
- 15. SINGLE BLINDED RANDOM CONTROLLED TRIAL: A single blind RCT is when the investigator knows but not the study participants known which treatment has been allocated (only participant unaware of the treatment receive) DOUBLE BLINDED RANDOM CONTROLLED TRIAL: A double blinding is when neither the investigator (clinician / data collector)nor the study participants is aware of treatment assignment. TRIPLE BLINDED RANDOM CONTROLLED TRIAL: A triple blinded study where participants , investigators (clinician/ data collectors),evaluator (data analysts/ statistician) are all unaware of the treatment the participants receives.