Randomization is the process by which allocation of subjects to treatment groups is done by chance, without the ability to predict who is in what group. It is done in clinical trials. This presentation describes the methods of randmization used in clinical trials.
Randomization is the process by which allocation of subjects to treatment groups is done by chance, without the ability to predict who is in what group. It is done in clinical trials. This presentation describes the methods of randmization used in clinical trials.
An epidemiological experiment in which subjects in a population are randomly allocated into groups, usually called study and control groups to receive and not receive an experimental preventive or therapetuic procedure, maneuver, or intervention .
inform consent form before participate in clinical trials.for purpose of understanding the nature of research,risk,benefits,and decision about participation
Randomized control trial is so called because the patients who constitute the unit of study are allocated into ‘study group’ and ‘control group’ at random depending upon whether they receive or do not receive the intervention.
An epidemiological experiment in which subjects in a population are randomly allocated into groups, usually called study and control groups to receive and not receive an experimental preventive or therapetuic procedure, maneuver, or intervention .
inform consent form before participate in clinical trials.for purpose of understanding the nature of research,risk,benefits,and decision about participation
Randomized control trial is so called because the patients who constitute the unit of study are allocated into ‘study group’ and ‘control group’ at random depending upon whether they receive or do not receive the intervention.
Steps in conducting a RCT
1. Drawing up a protocol
2. Selecting Reference & Experimental population
3. Randomization
4. Manipulation or Intervention
5. Follow up
6. Assessment of outcome
1. Drawing up a protocol
Aims and objectives of the study
Questions to be answered
Criteria for the selection of study and control groups
Size of the sample & allocation of subjects in both groups
Treatment to be applied - when, where, how
Standardization of working procedures and
Schedules as well as responsibilities of persons involved in the trial up to the stage of evaluation of outcome of the study.
2. Selecting Reference and Experimental Populations
Reference or target population - Population to which the findings of the trial, if found successful, are expected to be applicable (Eg: drugs, vaccines, etc.)
Experimental or Study population
Derived from the Reference population
Has same characteristics as the Reference population
Actual population that participates in the experimental study
Must give informed consent - Should be qualified or eligible for the trial
3. Randomization
Heart of the control trial
Procedure:
Participants are allocated into study and control groups
Eliminates bias and allows comparability
By random allocation every individual gets an equal chance for being allocated in to either groups.
4. Manipulation/ Intervention
Having formed the study and control group, the next step is to intervene or manipulate the study (experimental) group by deliberate application or withdrawal or reduction of a suspected causal factor
Eg: Drug, Vaccine, Dietary component, a habit
5. Follow up
Implies examination of the experimental and control group subjects at defined intervals of time in a standard manner, with equal intensity, under the same given circumstances in the same time frame till final assessment of outcome.
Attrition:
Inevitable losses to follow up (death, migration, loss of interest)
6. Assessment
a. Positive results:
Reduced incidence or severity of disease
Reduced cost to health service
Appropriate outcome in the study
b. Negative results:
Increased severity or frequency of side effects
Complications
Deaths
BIAS:
Any systematic error in the determination of association and outcome.
Bias may arise from errors of assessment of outcome due to human element
Subjective bias
Observer bias
Evaluation bias
1. Subjective Bias:
Participants, subjectively feel better or report improvement if they knew they were receiving a new form of treatment. This is known as “Subject variation”.
2. Observer Bias:
Investigator measuring the outcome of a therapeutic trial may be influenced if he knows beforehand the particular procedure or therapy to which the patient has been subjected.
3. Evaluation Bias:
Investigator may subconsciously give a favorable report of the outcome of the trial.
Blinding:
1. Single Blind Trial: Participant
2. Double Blind: Partcipant + Investigator
3. Triple Blind: Participant + Investigator + Data Analyzer
Methods of randomisation in clinical trialsAmy Mehaboob
Randomization is the process by which allocation of subjects to treatment groups is done by chance, without the ability to predict who is in what group. A randomized clinical trial is a clinical trial in which participants are randomly assigned to separate groups that compare different treatments.
Randomized trials are gold standard of study designs because the potential for bias (selection into treatment groups) is avoided.
This document includes the purpose, types, advantages and disadvantages of each type of randomisation.
Excelsior College PBH 321 Page 1 EXPERI MENTAL E.docxgitagrimston
Excelsior College PBH 321
Page 1
EXPERI MENTAL E PIDE MIOLOGICAL STUDIE S
Epidemiologic studies are either observational or experimental. Observational studies, including ecologic,
cross-sectional, cohort, and case-control designs, are considered “natural” experiments, but experimental
studies are considered true experiments. We will spend the next 2 modules discussing these designs.
Before we begin to discuss study designs, we need a brief introduction to a concept that we will spend more
time discussing in later modules -- bias. The definition of bias is:
“Deviation of results or inferences from the truth, or processes leading to such deviation. Any trend in the
collection, analysis, interpretation, publication, or review of data that can lead to conclusions that are
systematically different from the truth.” (Last, J.M., A Dictionary of Epidemiology, 4th ed.)
Epidemiologists are naturally concerned whether the results of an epidemiologic study are biased, since many
important public health decisions are often drawn from epidemiologic research. The severity of the bias, that
is - how much it influences or distorts the results, is related to the study design as well as how information is
analyzed.
Experimental Studies
The defining feature of experimental studies is that the investigator assigns exposure to the study subjects.
Experimental studies most closely resemble controlled laboratory experiments and serve as models for the
conduct of observational studies, thus they are the “gold standard” of epidemiologic research. Experimental
studies have high validity (i.e., less bias), and can identify even very small effects. The most well known type of
experimental study is a randomized trial (sometimes referred to as a randomized controlled trial), where the
investigator randomly assigns exposure to the study subjects. In this type of study, the only expected
difference between the experimental and control groups is the outcome variable being studied.
Experimental designs like the randomized trial can assess both preventive interventions, where a prophylactic
agent is given to healthy or high-risk individual to prevent disease, or can assess effects of therapeutic
treatment, such as those given to diseased individuals to reduce their risk of disease recurrence, or to improve
their survival or quality of life.
Preventive intervention: Does tamoxifen lower the incidence of breast cancer in women with high risk profile
compared to high risk women not given tamoxifen?
Therapeutic intervention: Do combinations of two or three antiretroviral drugs prolong survival of AIDS
patients as well as regimens of single drugs?
The investigator can assign exposures (or allocate interventions) to either individuals or to an entire
community.
Individual-level assignment: Do women with stage I breast cancer given a lumpectomy alone survive as long
without recurrence of disease as women given a lumpec ...
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Title: Sense of Smell
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the primary categories of smells and the concept of odor blindness.
Explain the structure and location of the olfactory membrane and mucosa, including the types and roles of cells involved in olfaction.
Describe the pathway and mechanisms of olfactory signal transmission from the olfactory receptors to the brain.
Illustrate the biochemical cascade triggered by odorant binding to olfactory receptors, including the role of G-proteins and second messengers in generating an action potential.
Identify different types of olfactory disorders such as anosmia, hyposmia, hyperosmia, and dysosmia, including their potential causes.
Key Topics:
Olfactory Genes:
3% of the human genome accounts for olfactory genes.
400 genes for odorant receptors.
Olfactory Membrane:
Located in the superior part of the nasal cavity.
Medially: Folds downward along the superior septum.
Laterally: Folds over the superior turbinate and upper surface of the middle turbinate.
Total surface area: 5-10 square centimeters.
Olfactory Mucosa:
Olfactory Cells: Bipolar nerve cells derived from the CNS (100 million), with 4-25 olfactory cilia per cell.
Sustentacular Cells: Produce mucus and maintain ionic and molecular environment.
Basal Cells: Replace worn-out olfactory cells with an average lifespan of 1-2 months.
Bowman’s Gland: Secretes mucus.
Stimulation of Olfactory Cells:
Odorant dissolves in mucus and attaches to receptors on olfactory cilia.
Involves a cascade effect through G-proteins and second messengers, leading to depolarization and action potential generation in the olfactory nerve.
Quality of a Good Odorant:
Small (3-20 Carbon atoms), volatile, water-soluble, and lipid-soluble.
Facilitated by odorant-binding proteins in mucus.
Membrane Potential and Action Potential:
Resting membrane potential: -55mV.
Action potential frequency in the olfactory nerve increases with odorant strength.
Adaptation Towards the Sense of Smell:
Rapid adaptation within the first second, with further slow adaptation.
Psychological adaptation greater than receptor adaptation, involving feedback inhibition from the central nervous system.
Primary Sensations of Smell:
Camphoraceous, Musky, Floral, Pepperminty, Ethereal, Pungent, Putrid.
Odor Detection Threshold:
Examples: Hydrogen sulfide (0.0005 ppm), Methyl-mercaptan (0.002 ppm).
Some toxic substances are odorless at lethal concentrations.
Characteristics of Smell:
Odor blindness for single substances due to lack of appropriate receptor protein.
Behavioral and emotional influences of smell.
Transmission of Olfactory Signals:
From olfactory cells to glomeruli in the olfactory bulb, involving lateral inhibition.
Primitive, less old, and new olfactory systems with different path
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Type of randomization
1. TYPES OF RANDOMIZATION
Guided by
Dr. Jigna S. Shah
Presented by
Mr. Bharat Kumar
17MPH202
Department of Pharmacology, Institute of
Pharmacy,
Nirma university, Ahmedabad.
2. Randomization
A method based on chance alone by which study
participants are assigned to a treatment group.
Randomization minimizes the differences among
groups by equally distributing people with particular
characteristics among all the trial arms. The
researchers do not know which treatment is better.
3.
4. Need of Randomization
If, at the end of a clinical trial, a difference in outcomes
occurs between two treatment groups (say, intervention
and control) possible explanations for this difference
would include:
1. the intervention exhibits a real effect;
2. the outcome difference is solely due to chance
3. there is a systematic difference (or bias) between
the groups due to factors other than the intervention.
Randomization aims to obviate the third possibility.
5. Criteria for randomization
1. 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.
2. 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
3. Simplicity
• Easy for investigator/staff to implement
6. Forms of Randomization
• Simple Randomization
• Block Randomization
• Stratified Block Randomization
• Dynamic (adaptive) random allocation
7. Simple Randomization
• Randomization based on a single sequence of random
assignments
• basic method of simple randomization is flipping a coin
• Computer generated sequence
• 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.
8. Simple Randomization
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.
9. Block Randomization
• The block randomization method is designed to
randomize subjects into groups that result in equal sample
sizes
• used to ensure a balance in sample size across groups
over time
• Used for small studies to maintain reasonably good
balance among groups
• In a two group design, Blocks having equal numbers of
As and Bs (A = intervention and B = control, for
example) are used, with the order of treatments within the
block being randomly permuted
10. Illustration
With a block size of 4 for two groups(A,B), there are 6
possible permutations and they can be coded as:
1=AABB, 2=ABAB, 3=ABBA, 4=BAAB, 5=BABA,
6=BBAA
Each number in the random number sequence in turn
selects the next block, determining the next four
participant allocations (ignoring numbers 0,7,8 and 9).
e.g., The sequence 67126814…. will produce BBAA
AABB ABAB BBAAAABB BAAB.
11. Stratified Block Randomization
• The stratified randomization method addresses the need to
control and balance the influence of covariates
• This method can be used to achieve balance among groups
in terms of subjects’ baseline characteristics (covariates).
• Typical examples of such factors are age group, severity of
condition, and treatment centre. Stratification simply
means having separate block randomisation schemes for
each combination of characteristics (‘stratum’)
• For example, in a study where you expect treatment effect
to differ with age and sex you may have four strata: male
over 65, male under 65, female over 65 and female under
65
12. Dynamic (adaptive) random
allocation
Simple and block randomization methods are defined, and
allocation sequences set up, before the start of the trial.
In contrast, dynamic randomization methods allocate patients
to treatment group by checking the allocation of similar
patients already randomized, and allocating the next treatment
group "live" to best balance the treatment groups across all
stratification variables. Biased coin randomization and
minimisation are two such methods.
13. Inappropriate randomisation
methods
• Assigning patients alternately to treatment group is
not random assignment
• Assigning the first half of the population to one
group is not random assignment
• Assignments by methods based on patient
characteristics such as date of birth, order of entry
into the clinic or day of clinic attendance, are not
reliably random
14. Bias
Bias is said to have occurred if the results observed
reflect other factors in addition to (or even instead of) the
effect of the treatment:
Some potential sources of bias:
• Selection bias
• Performance bias
• Detection bias
• Laboratory bias
• Sample size bias
15. Selection bias
Selection bias is concerned with two main issues:
• systematic differences arise between the sampling
population and the sample drawn and,
• systematic differences arise between treatment groups
at the outset of the trial, usually due to individuals
either tampering with or predicting the allocation
sequence.
16. Performance Bias
Performance bias is the tendency for participants to
change their behavior or responses to questions because
they are aware of being in a trial and of their treatment
allocation.
17. Detection Bias
Detection bias is concerned primarily with blinding.
In this case, however, the concern is about those
collecting the data, not those providing it.
The Cochrane Handbook warns that if “outcome
assessors are aware of assignments, bias could be
introduced into assessments of outcome, depending
on who measures the outcomes.”
18. Laboratory Bias
• the knowledge of which treatment the patient
received may affect the way in which the test is run
or interpreted, or be retested.
• although this is most severe with subjectively graded
results (pathology slides, photographs, ECG, etc.),
this can also be a problem with "objective tests" such
as laboratory assays which may be run subtly
differently by the technician.
19. Sample size bias
Sample size calculations are a deceptively simple tool to
minimize bias – an insufficiently large sample size can lead
to imprecise estimation, biasing the results downward.
20. Blinding
Blinding is a procedure in which one or more parties in a
trial are kept unaware of which treatment arms participants
have been assigned to, in other words, which treatment was
received. Blinding is an important aspect of any trial done in
order to avoid and prevent conscious or unconscious bias in
the design and execution of a clinical trial.
Blinding (also called masking or concealment of
treatment) is intended to avoid bias caused by subjective
judgment in reporting, evaluation, data processing, and
analysis due to knowledge of treatment.
21. Types of Blinding
• Unblinded or open label : All parties are aware of the
treatment the participant receives
• Single blind or single-masked : Only the participant is
unaware of the treatment they receive
• Double blind or double-masked : The participant and the
clinicians / data collectors are unaware of the treatment the
participant receives
• Triple blind : Participant, clinicians / data collectors and
outcome adjudicators / data analysts are all unaware of the
treatment the participant receives
22. Open Label Studies
Open Label clinical trials do not attempt to disguise the new drug
or treatment, meaning that no standard treatment or placebo is
utilized. This leans towards bias, as both the patient and the
physician are aware of which groups are receiving what type of
treatment.
These may be useful for
• pilot studies
• dose ranging studies
However, even these applications may be substantially biased by
knowledge of the treatment given and may result in
• toxicity over (or under) reported
• efficacy over estimated
23. Single Blind Studies
• The participants in the clinical trial do not know if they are
receiving the placebo or the real treatment.
• This is done to reduce the risk of errors, since some
participants might produce spurious results if they know that
they are taking the placebo or medication.
• In this model, the experimenter monitoring the participants
knows which individuals received the placebo and which
ones got the treatment under examination.
24. Double Blind Studies
• When both the subjects and the investigators are kept from knowing
who is assigned to which treatment, the experiment is called “double
blind"
• This is considered to be the superior model of clinical research since it
eliminates outcomes that are produced due to placebo effect, as well
as observer bias by the experimenter. The fact that the experimenter
does not know which group received the placebo or the experimental
drug means that the risk of conscious and unconscious observer bias is
reduced, making the study more accurate.
25. Triple Blinding
The treatment or intervention is unknown to
(a) the research participant,
(b) the individual(s) who administer the treatment or
intervention, and
(c) the individual(s) who assess the outcomes.
The terms blind and masking are synonymous; both terms
describe methods that heslp to ensure that individuals do not
know which treatment or intervention is being administered.
The purpose of triple-blinding procedures is to reduce
assessment bias and to increase the accuracy and objectivity of
clinical outcomes.
26. Reference
• “An overview of randomization techniques: An unbiased assessment of
outcome in clinical research” J Hum Reprod Sci. 2011 Jan-Apr; 4(1): 8–11,
doi: 10.4103/0974-1208.82352
• “Designing a research project: randomised controlled
trials and their principles” - J M Kendall
• Triple-Blind Study , In: Encyclopedia of Research Design - Neil J. Salkind,
DOI: http://dx.doi.org/10.4135/9781412961288.n471
• “Risk and evidence of bias in randomized controlled trials” – Alex Eble
and Peter Boone, june 2012
• https://www.biopharmainstitute.com/faq/what-is-the-difference-between-
single-blind-and-double-blind-clinical-trials
• “Randomization in clinical trial, recruitment , inclusion and exclusion
criteria” – Dr Urmila M. Aswar , pune
• “The concept of randomization and blinding in clinical trials” – Suraj P
Anand