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PHC215
By Dr. Khaled Ouanes Ph.D.
E-mail: [email protected]
Twitter: @khaled_ouanes
INTRODUCTION TO
HEALTHCARE RESEARCH
METHODS
Experimental Studies
An experimental study assigns participants tointervention and control groups in order toexamine whether an intervention causes anintended outcome.
Because the researcher assigns participants toreceive a particular exposure, the exacttiming, dose, duration, and frequency of theexposure are known.
Framework
for an
Experimental
Study.
Randomized Controlled Trials (RCTs)
In a randomized controlled trial (RCT):
Some participants are randomly assigned to an
active intervention group
The remaining participants are assigned to a
control group
All participants from both groups are followed
forward in time to see who has a favorable
outcome and who does not
Describing the Intervention
The research plan should carefully define:
What the intervention will be
Where and how participants will receive the
intervention
When, how often, and for what duration
participants will receive the intervention
Eligibility and aptness criteria for participants
Defining Outcomes
Most experimental studies are superiority trialsthat aim to demonstrate that a new interventionis “better” than some type of control.
Because the term “better” can be defined in somany ways, the researcher must beforehandand carefully define what constitutes afavorable outcome for the experiment.
Types of Success
Examples of
Favorable
Outcomes
Selecting Controls
Experimental studies usually assign some participants to the active intervention and the remainder to a control group.
SO WHAT TYPES OF CONTROLS CAN WE HAVE?
1. The most typical control is a placebo, an inactive comparison that is similar to the therapy being tested
2. Sometimes the new therapy is compared to some existing “industry standard of care” or other therapy
3. Sometimes varying doses and durations of a therapy may be compared to one another
Selecting Controls
Examples of Types of Controls
Examples of Types of Controls
Hawthorne bias
Hawthorne effect: (observer effect) is a type of
reactivity in which participants in a study may
change their behavior for the better simply
because they know they are being observed
This may interfere with the accurate
measurement of the impact of the new
intervention.
Blinding
Blinding or masking:
Participants in an experimental study do not know whether they are in the active intervention
group or the control group.
Blinding minimizes information bias
Blinding
There are 2 main cases:
In a single-blind study, participants are unaware oftheir exposure status
In a double-blind study, neither the participants northe persons assessing the participants’ health statusknow which participants are in the active and controlgroups.
Randomization
A variety of approaches can be used torandomly allocate participants to an activeintervention group or a control group:
Simple randomization
Block randomization
Stratified randomization
Examples of Types of
Randomization
Strata: Homogeneous
subgroups of
members in the population
Ethical Considerations
Experimental studies involve a particularly high level of ethical risk because the researcher assigns participants to exposures that the participants do not choose and may have
been unlikely to encounter in normal life had they not volunteered to participate in a
research project.
Ethical Principles
Clinical Equipoise or equipoise principal:
It provides the ethical basis for medical research
that involves assigning patients to different
treatments of a clinical trial. The term was first used
by Benjamin Freedman in 1987. It states that
experimental research should be conducted only
when there is genuine uncertainty about which
treatment will work better
Ethical Principles
Distributive justice: infers that the source
population must be an appropriate and non-
exploitative one
Beneficence (doing good) and non-maleficence
(do not harm): researchers must balance the
likely benefits and risks of the study. Otherwise the
study should not be conducted.
Respect for persons:
Participants must volunteer for a study without being unduly influenced by the prospect of being compensated for their participation
Participants must be able to understand what it means to be a research subject, including the possibility of being assigned to a control group instead of the new intervention
Ethical Principles
Examples of Ethical Issues to
Consider When Planning an
Experimental Study
AnalysisExperimental studies use many of the same measures of association that cohort studies do:
Relative rates (RRs)
Attributable risks (ARs, AR%s)
Measures of survival
Experimental studies use these measures to examine the impact of an assigned exposure on the likelihood of having either a favorable or unfavorable outcome.
Analysis: Efficacy
Efficacy: the proportion of individuals in the control group who experience an unfavorable outcome
who could have been expected to have a
favorable outcome had they been in the active
group instead of control.
A high efficacy is an indicator that an intervention
is successful.
Analysis: NNT
Number needed to treat (NNT): the expected number of
people who would have to receive a treatment to
prevent an unfavorable outcome in one person (or,
alternately stated, to achieve a favorable outcome in
one person)
A small NNT indicates a more effective intervention.
If a drug is intended to prevent stroke and has an NNT of 5, then 5 people have to take the drug for one year (or some other chosen time span) to prevent one of the 5 from having a stroke.
If a drug has an NNT of 100, it means that 100 people have to take the drug to prevent one of the 100 from having a stroke.
Analysis: NNT
Stratification of patients for efficacy can
substantially reduce the number
needed to treat for benefit.
Matthews, P. M. et al (2013 )
In the example depicted in the previous slide, 22% of
patients respond to a given treatment, so
approximately 5 patients need to be treated to benefit
one patient (NNT=5). If the population is stratified to
enrich the treated population with responders
(identified through testing), the number needed to treat
for benefit will decrease. In this example, a
stratification approach with 90% sensitivity and
specificity is assumed.
Efficacy & Number Needed to Treat
(NNT)
Analytic Frameworks
Treatment-received approach: limit analysis to the participants who were fully compliant with
their assigned intervention
Treatment-assigned approach (intention-to-
treat approach): includes all participants even
if they were not fully compliant with their
assigned intervention
Flow of Participants in an
Experimental Study
Ke
y C
ha
rac
terist
ics
of
Exp
erim
en
tal st
ud
ies
Screening & Diagnostic Tests
The goal of some studies is to compare two tests that are supposed to measure the same
thing, such as comparing the results of an antibody test for cancer to biopsy results
Sensitivity = Of those who have the disease, what % test positive?
Specificity = Of those who do not have the
disease, what % test negative?
Screening & Diagnostic Tests
Positive predictive value (PPV) = Of those who test positive, what % actually have the
disease?
Negative predictive value (NPV) = Of those
who test negative, what % actually do not
have the disease?
Screening & Diagnostic Tests
Test
Results
Tests of Agreement
Tests of inter-observer agreement (concordance) can
be used to determine the extent of agreement between
two assessors who are evaluating the same study
participants
Example: a measurement known as the kappa statistic can
indicate whether two radiologists examining the same set of X-rays
reach the same conclusion about the presence or absence of a
fracture more or less often than can be expected by chance
Qualitative Studies
Qualitative Study Methods
A qualitative study looks for the themes and meanings that emerge from the observation
and evaluation of a situation or context.
Researchers have intense contact with a selected group of informants.
Examples of Approaches
Phenomenology: seeks to understand how participants understand, interpret, and find meaning in their own
unique life experiences and feelings
Grounded theory: an inductive reasoning process that
uses observations to develop general theories that
explain human behavior
Ethnography: aims to develop an insider’s view (an emic
perspective) of how members of a particular Ethnic or
cultural group see their world
Examples of Techniques
In-depth and semi-structured interviews of individuals use open-ended questions to explore viewpoints. The interviewer is allowed to probe for more details about any response in order to gain fuller understanding of the participant’s experiences and perspectives.
Interviews are often supplemented by other methods, such as participant diaries or journals.
Focus groups of about 4 to 12 people are moderated discussions led by a facilitator
from the research team. The facilitator
encourages participants to interact with
one another and to clarify their individual
and shared perspectives.
Examples of Techniques
Examples of Analytic Techniques
The analysis of qualitative data usually involves coding
and classifying observations and deriving major and
minor themes from the groups of observations.
Reports of the findings of qualitative studies often
incorporate quotations that express participants’
perspectives and experiences in their own words.
Consensus Methods
The goal of some studies is to identify areas of consensus and areas of contention among individuals who are experts on a particular
topic and/or a particular community or organization.
Delphi Method
The Delphi method is a structured decision-making and
forecasting process in which participants engage in several
rounds of:
Completing individual questionnaires
A facilitator summarizing and sharing the responses
Panelists reconsidering their perspectives after reflecting
on the opinions expressed by others
The goal is for each iteration to move the panel of experts
closer to agreement.
De
lph
i M
eth
od
Program Evaluation
Program evaluation includes a variety of approaches
for provide feedback about what is working well and
what can and should be improved
The evaluation approach must match the goals of the
assessment
After gathering evidence from a variety of sources,
practical suggestions are made based on the
conclusions of the assessment
Evidence is reviewed and categorized using a framework like
SWOT:
Strengths (internal organizational strengths)
Weaknesses (internal organizational limitations)
Opportunities (external strengths)
Threats (external limitations, which might be political, economic,
sociocultural, technological, environmental, or legal)
Program Evaluation
Pro
gra
m E
va
lua
tio
n
A similar process can be used as a
component of other forms of evaluative
research, such as:
Needs assessment.
Cost-effectiveness analysis
Health services research
Program Evaluation
PHC215
By Dr. Khaled Ouanes Ph.D.
E-mail: [email protected]
Twitter: @khaled_ouanes
HEALTHCARE RESEARCH METHODS
Based on the textbook of introduction to health research methods – K.H. Jacobsen