This document discusses different study designs used in public health research, including observational and interventional studies. Observational studies include cross-sectional, case-control and cohort studies. Cross-sectional studies collect data at one point in time to measure disease prevalence. Case-control studies compare exposures in cases (people with disease) versus controls (people without disease). Cohort studies follow groups over time to measure disease incidence and identify risk factors. Interventional studies, like randomized controlled trials, are considered the strongest type of evidence as they involve intervention to reduce exposure or compare alternative treatments.
The Randomized Controlled Trial: The Gold Standard of Clinical Science and a ...marcus evans Network
Tim Fayram, St. Jude Medical Inc. - Speaker at the marcus evans Medical Device R&D Summit Fall 2013, held in Palm Beach, FL delivered his presentation entitled The Randomized Controlled Trial: The Gold Standard of Clinical Science and a Barrier to Innovation?
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 .
The Randomized Controlled Trial: The Gold Standard of Clinical Science and a ...marcus evans Network
Tim Fayram, St. Jude Medical Inc. - Speaker at the marcus evans Medical Device R&D Summit Fall 2013, held in Palm Beach, FL delivered his presentation entitled The Randomized Controlled Trial: The Gold Standard of Clinical Science and a Barrier to Innovation?
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 .
Some types of studies require unblinded personnel at the site and a matching unblinded monitoring and study management team. This presentation provides a little background on blinding and then reviews best practices for unblinding.
Jonas Ranstam MedicReS World Congress 2013MedicReS
Practical and statistical aspects of randomization
and blinding in clinical trials
Jonas Ranstam PhD
Department of Clinical Sciences
Lund University
Sweden
Freshers in clinical research and regulatory affairs must go through this presentation. It will help you to understand the basis of clinical trial design as per European guidelines, which is the most preferred reference guideline. Initially, I also faced many problems to understand this concept. A student who is studying a clinical research diploma can also use this presentation for their basic understanding.
Blinded clinical trials only became standardized into their current form in the 1980s. The history before this very recent phenomenon has become almost invisible, even though it was challenged right from the start by the AIDS crisis. The challenge to the RCT as the principle image of clinical research continues with the Ebola crisis and Right to Try legislation.
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.
Comparing research designs fw 2013 handout versionPat Barlow
This is an updated version of my Comparing Research Designs lecture, which now includes discussions on: (1) common considerations with research design such as bias, reliability, validity, and confounding; and (2) expanded discussion of RCT designs including factorial and cross-over designs.
Some types of studies require unblinded personnel at the site and a matching unblinded monitoring and study management team. This presentation provides a little background on blinding and then reviews best practices for unblinding.
Jonas Ranstam MedicReS World Congress 2013MedicReS
Practical and statistical aspects of randomization
and blinding in clinical trials
Jonas Ranstam PhD
Department of Clinical Sciences
Lund University
Sweden
Freshers in clinical research and regulatory affairs must go through this presentation. It will help you to understand the basis of clinical trial design as per European guidelines, which is the most preferred reference guideline. Initially, I also faced many problems to understand this concept. A student who is studying a clinical research diploma can also use this presentation for their basic understanding.
Blinded clinical trials only became standardized into their current form in the 1980s. The history before this very recent phenomenon has become almost invisible, even though it was challenged right from the start by the AIDS crisis. The challenge to the RCT as the principle image of clinical research continues with the Ebola crisis and Right to Try legislation.
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.
Comparing research designs fw 2013 handout versionPat Barlow
This is an updated version of my Comparing Research Designs lecture, which now includes discussions on: (1) common considerations with research design such as bias, reliability, validity, and confounding; and (2) expanded discussion of RCT designs including factorial and cross-over designs.
This is the handout version of a lecture I give to medical residents and fellows on the basics of clinical research designs and the inherent issues that go along with each one. I give this lecture as part of a multi-module lecture series on research design and statistical analysis.
This is a lecture that I gave to a Principles of Epidemiology MPH class. It takes a critical look at the use of p-values to judge the strength of evidence, and offers more holistic, informative approaches to interpreting statistical findings such as measures of effect size and confidence intervals.
Excelsior College PBH 321 Page 1 CASE-CONTROL STU.docxgitagrimston
Excelsior College PBH 321
Page 1
CASE-CONTROL STUD IES
A case-control study is an observational design that involves studying a population in which cases of disease
are identified and enrolled, and a sample of the population that produced the cases is identified and enrolled
(controls). Exposures are determined for individuals in both groups.
Let’s say that we want to test the hypothesis that pesticide exposure increases the risk of breast cancer.
Consider a hypothetical prospective cohort study of 89,949 women aged 34-59; 1,439 breast cancer cases
were identified over 8 years of follow-up. Blood was drawn on all 89,949 at beginning of follow-up and
samples were frozen. The exposure was defined as the level of pesticides (e.g. DDE) in blood, characterized as
high or low. We compare women with high or low exposures to see if they got breast cancer or not by the end
of follow-up.
Breast Cancer
Yes No Total
DDE
exposure High 360 13,276 13,636
Relative Risk = RR = (360/13,636) / (1,079/76,313) = 1.9
Low 1,079 75,234 76,313
Women with high pesticide levels in the blood have 1.9
times the risk of developing breast cancer after 8 years
than women with low levels
Total 1,439 88,510 89,949
Conducting this study presents a practical problem: quantifying pesticide levels in the blood is very expensive -
-it's not feasible to analyze all 89,949 blood samples (this would cost many thousands of dollars).
To be efficient, we could instead analyze blood on all breast cancer cases (N=1,439) but take only a sample of
the women who did not get breast cancer, say two times as many cases (N=2,878) (controls). This is a case-
control study! Specifically, because we sampled cases and controls from within a complete cohort, we refer to
this as a nested case-control study.
Breast Cancer
Cases Controls
DDE
exposure
High 360 432
Low 1,079 2,446
Total 1,439 2,878
Excelsior College PBH 321
Page 2
Timing and Set Up of a Case-Control Study
Cases
When identifying cases, the criteria for the case definition should lead to accurate classification of disease.
This means the investigator must have efficient and accurate sources to identify cases, such as existing disease
registries or hospitals.
In our standard 2 x 2 table, the number of cases gives you the numerators of the rates of disease in exposed
and unexposed groups being compared.
Disease
Yes
(cases)
No
(controls)
Total
Exposure Yes a ? ? Rate of disease in exposed: a/?
No c ? ?
Rate of disease in
unexposed: c/?
Total a+c ? ?
What is missing? The denominators! If this were a cohort study, you would have the total population (if you
were calculating cumulative incidence) or total person-years (if you were calculating incidence rates) for both
the exposed and non-exposed groups, which would provide the c ...
Observational research designs are those in which the researcher/investigator merely observes and does not carry out any interventions/actions.
to change the result. The three most common types of observational studies are cross-sectional studies, case-control studies, and cohort (or longitudinal) studies.
In cross-sectional studies, exposure/risk factors and outcomes are determined at a single point in time. You can bid
information on disease prevalence and an overview of likely relationships that can be used to form a hypothesis. Control cases In
studies, participants are selected based on the presence/absence of an outcome and risk factors are identified during the study.
after enrollment of study participants.The relationship between exposure and outcome is reported as an odds ratio. This research; However,
carries a high risk of bias, which should be taken into account when designing the study. Cohort studies are prospective and include participants
were selected based on presence/absence of exposure and results were obtained at the end of the study. This research can deliver The incidence/impact of the disease and the relationship between exposure and outcome are presented as relative risks. They are useful
establish causality.A problem that arises in these studies could be the high fluctuation and dropout of study participants.
Descriptive studies generally describe the magnitude of a problem and characteristics of the population/individuals.
The various types of such studies include
case reports
case series or surveys.
A case report generally describes a patient presenting with an unusual disease, or simultaneous occurrence of more than one condition, or uncommon clinical features in a known disease.
A case series is a collection of similar cases. Such studies, other than providing some advancement to knowledge of a disease, are of limited value. Another method often used in epidemiological health care research is conducting surveys.
Surveys are done during a defined time-period and information on several variables of interest is collected from the target population. They provide estimates of prevalence of the various variables of interest, and their distribution. Such studies could also provide insight into individual opinions and practices. Advantages include ease of conduct and cost efficiency. The disadvantages include low response rates and a variety of biases.
An analytical study tests a hypothesis to determine an association between two or more variables, like causation, risk, or effect. Such studies have two or more study groups for comparison.
The primary focus of this article will be the three most common types of analytical observational studies –
cross-sectional,
case control (also known as retrospective) and
cohort (or longitudinal, also known as prospective) studies.
It may be pertinent to note that the primary objective of most clinical studies is to determine one of the following - burden of disease (prevalence
The STUDY of the DISTRIBUTION & DETERMINANTS of HEALTH-RELATED STATES in specified POPULATIONS, and the application of this study to CONTROL of health problems.
Analytic StudiesThere are basically two types of studies experi.docxrossskuddershamus
Analytic Studies
There are basically two types of studies: experimental and observational. In an experimental study, the exposure has not occurred yet. The investigator controls the exposure in the study groups and studies the impact. For example, he may immunize one group with an experimental vaccine that has been developed for a disease and compare the frequency with which the disease develops to the control group (which had no modification). In an observational study, the exposure has already occurred. The exposures and outcomes are observed and analyzed, not created experimentally. Observational studies are often more practical and continue to provide the major contribution to our understanding of diseases. There are two main types of observational studies: cohort (prospective) and case-control (retrospective) studies.
In a cohort study, a group of people who share a common experience within a defined time period (cohort) are categorized based upon their exposure status. For example, individuals at a work place where an asbestos exposure occurred would be considered a cohort. Another example would be individuals attending a wedding where a foodborne illness occurred. Cohort studies have well-defined populations. Often, cohort studies involve following a cohort over time in order to determine the rate at which a disease develops in relation to the exposure.
In a cohort study, relative risk is used to determine whether an association exists between an exposure and a disease. Relative risk is defined as ratio of the incidence rate among exposed individuals to the incidence rate among unexposed individuals.
To calculate the relative risk, you would use the following formula: (a/a+b) / (c/c+d) where:
a = the number of individuals with a disease who were exposed.
b = the number of individuals without a disease who were exposed.
c = the number of individuals with a disease who were NOT exposed.
d = the number of individuals without a disease who were NOT exposed.
In a case-control study, the sample is based upon illness status, rather than exposure status. The researcher identifies a group of people who meet the case definition and a group of people who do not have the illness (controls). The objective is to determine if the two groups differ in the rate of exposure to a specific factor or factors.
In contrast to a cohort study, the total number of people exposed in a case-control study is unknown. Therefore, relative risk cannot be used. Instead, an odds ratio or risk ratio is used. An odds ratio measures the odds that an exposed individual will develop a disease in comparison to an unexposed individual. Please click the button below to learn how to calculate an odds ratio.
To calculate an odds ratio, you would use the following formula: ad/bc
where:
a = the number of individuals with a disease who were exposed.
b = the number of individuals without a disease who were exposed.
c = the number of individu.
Basavarajeeyam is an important text for ayurvedic physician belonging to andhra pradehs. It is a popular compendium in various parts of our country as well as in andhra pradesh. The content of the text was presented in sanskrit and telugu language (Bilingual). One of the most famous book in ayurvedic pharmaceutics and therapeutics. This book contains 25 chapters called as prakaranas. Many rasaoushadis were explained, pioneer of dhatu druti, nadi pareeksha, mutra pareeksha etc. Belongs to the period of 15-16 century. New diseases like upadamsha, phiranga rogas are explained.
ARTIFICIAL INTELLIGENCE IN HEALTHCARE.pdfAnujkumaranit
Artificial intelligence (AI) refers to the simulation of human intelligence processes by machines, especially computer systems. It encompasses tasks such as learning, reasoning, problem-solving, perception, and language understanding. AI technologies are revolutionizing various fields, from healthcare to finance, by enabling machines to perform tasks that typically require human intelligence.
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Ve...kevinkariuki227
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Verified Chapters 1 - 19, Complete Newest Version.pdf
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Verified Chapters 1 - 19, Complete Newest Version.pdf
Ozempic: Preoperative Management of Patients on GLP-1 Receptor Agonists Saeid Safari
Preoperative Management of Patients on GLP-1 Receptor Agonists like Ozempic and Semiglutide
ASA GUIDELINE
NYSORA Guideline
2 Case Reports of Gastric Ultrasound
Tom Selleck Health: A Comprehensive Look at the Iconic Actor’s Wellness Journeygreendigital
Tom Selleck, an enduring figure in Hollywood. has captivated audiences for decades with his rugged charm, iconic moustache. and memorable roles in television and film. From his breakout role as Thomas Magnum in Magnum P.I. to his current portrayal of Frank Reagan in Blue Bloods. Selleck's career has spanned over 50 years. But beyond his professional achievements. fans have often been curious about Tom Selleck Health. especially as he has aged in the public eye.
Follow us on: Pinterest
Introduction
Many have been interested in Tom Selleck health. not only because of his enduring presence on screen but also because of the challenges. and lifestyle choices he has faced and made over the years. This article delves into the various aspects of Tom Selleck health. exploring his fitness regimen, diet, mental health. and the challenges he has encountered as he ages. We'll look at how he maintains his well-being. the health issues he has faced, and his approach to ageing .
Early Life and Career
Childhood and Athletic Beginnings
Tom Selleck was born on January 29, 1945, in Detroit, Michigan, and grew up in Sherman Oaks, California. From an early age, he was involved in sports, particularly basketball. which played a significant role in his physical development. His athletic pursuits continued into college. where he attended the University of Southern California (USC) on a basketball scholarship. This early involvement in sports laid a strong foundation for his physical health and disciplined lifestyle.
Transition to Acting
Selleck's transition from an athlete to an actor came with its physical demands. His first significant role in "Magnum P.I." required him to perform various stunts and maintain a fit appearance. This role, which he played from 1980 to 1988. necessitated a rigorous fitness routine to meet the show's demands. setting the stage for his long-term commitment to health and wellness.
Fitness Regimen
Workout Routine
Tom Selleck health and fitness regimen has evolved. adapting to his changing roles and age. During his "Magnum, P.I." days. Selleck's workouts were intense and focused on building and maintaining muscle mass. His routine included weightlifting, cardiovascular exercises. and specific training for the stunts he performed on the show.
Selleck adjusted his fitness routine as he aged to suit his body's needs. Today, his workouts focus on maintaining flexibility, strength, and cardiovascular health. He incorporates low-impact exercises such as swimming, walking, and light weightlifting. This balanced approach helps him stay fit without putting undue strain on his joints and muscles.
Importance of Flexibility and Mobility
In recent years, Selleck has emphasized the importance of flexibility and mobility in his fitness regimen. Understanding the natural decline in muscle mass and joint flexibility with age. he includes stretching and yoga in his routine. These practices help prevent injuries, improve posture, and maintain mobilit
Flu Vaccine Alert in Bangalore Karnatakaaddon Scans
As flu season approaches, health officials in Bangalore, Karnataka, are urging residents to get their flu vaccinations. The seasonal flu, while common, can lead to severe health complications, particularly for vulnerable populations such as young children, the elderly, and those with underlying health conditions.
Dr. Vidisha Kumari, a leading epidemiologist in Bangalore, emphasizes the importance of getting vaccinated. "The flu vaccine is our best defense against the influenza virus. It not only protects individuals but also helps prevent the spread of the virus in our communities," he says.
This year, the flu season is expected to coincide with a potential increase in other respiratory illnesses. The Karnataka Health Department has launched an awareness campaign highlighting the significance of flu vaccinations. They have set up multiple vaccination centers across Bangalore, making it convenient for residents to receive their shots.
To encourage widespread vaccination, the government is also collaborating with local schools, workplaces, and community centers to facilitate vaccination drives. Special attention is being given to ensuring that the vaccine is accessible to all, including marginalized communities who may have limited access to healthcare.
Residents are reminded that the flu vaccine is safe and effective. Common side effects are mild and may include soreness at the injection site, mild fever, or muscle aches. These side effects are generally short-lived and far less severe than the flu itself.
Healthcare providers are also stressing the importance of continuing COVID-19 precautions. Wearing masks, practicing good hand hygiene, and maintaining social distancing are still crucial, especially in crowded places.
Protect yourself and your loved ones by getting vaccinated. Together, we can help keep Bangalore healthy and safe this flu season. For more information on vaccination centers and schedules, residents can visit the Karnataka Health Department’s official website or follow their social media pages.
Stay informed, stay safe, and get your flu shot today!
Ethanol (CH3CH2OH), or beverage alcohol, is a two-carbon alcohol
that is rapidly distributed in the body and brain. Ethanol alters many
neurochemical systems and has rewarding and addictive properties. It
is the oldest recreational drug and likely contributes to more morbidity,
mortality, and public health costs than all illicit drugs combined. The
5th edition of the Diagnostic and Statistical Manual of Mental Disorders
(DSM-5) integrates alcohol abuse and alcohol dependence into a single
disorder called alcohol use disorder (AUD), with mild, moderate,
and severe subclassifications (American Psychiatric Association, 2013).
In the DSM-5, all types of substance abuse and dependence have been
combined into a single substance use disorder (SUD) on a continuum
from mild to severe. A diagnosis of AUD requires that at least two of
the 11 DSM-5 behaviors be present within a 12-month period (mild
AUD: 2–3 criteria; moderate AUD: 4–5 criteria; severe AUD: 6–11 criteria).
The four main behavioral effects of AUD are impaired control over
drinking, negative social consequences, risky use, and altered physiological
effects (tolerance, withdrawal). This chapter presents an overview
of the prevalence and harmful consequences of AUD in the U.S.,
the systemic nature of the disease, neurocircuitry and stages of AUD,
comorbidities, fetal alcohol spectrum disorders, genetic risk factors, and
pharmacotherapies for AUD.
New Directions in Targeted Therapeutic Approaches for Older Adults With Mantl...i3 Health
i3 Health is pleased to make the speaker slides from this activity available for use as a non-accredited self-study or teaching resource.
This slide deck presented by Dr. Kami Maddocks, Professor-Clinical in the Division of Hematology and
Associate Division Director for Ambulatory Operations
The Ohio State University Comprehensive Cancer Center, will provide insight into new directions in targeted therapeutic approaches for older adults with mantle cell lymphoma.
STATEMENT OF NEED
Mantle cell lymphoma (MCL) is a rare, aggressive B-cell non-Hodgkin lymphoma (NHL) accounting for 5% to 7% of all lymphomas. Its prognosis ranges from indolent disease that does not require treatment for years to very aggressive disease, which is associated with poor survival (Silkenstedt et al, 2021). Typically, MCL is diagnosed at advanced stage and in older patients who cannot tolerate intensive therapy (NCCN, 2022). Although recent advances have slightly increased remission rates, recurrence and relapse remain very common, leading to a median overall survival between 3 and 6 years (LLS, 2021). Though there are several effective options, progress is still needed towards establishing an accepted frontline approach for MCL (Castellino et al, 2022). Treatment selection and management of MCL are complicated by the heterogeneity of prognosis, advanced age and comorbidities of patients, and lack of an established standard approach for treatment, making it vital that clinicians be familiar with the latest research and advances in this area. In this activity chaired by Michael Wang, MD, Professor in the Department of Lymphoma & Myeloma at MD Anderson Cancer Center, expert faculty will discuss prognostic factors informing treatment, the promising results of recent trials in new therapeutic approaches, and the implications of treatment resistance in therapeutic selection for MCL.
Target Audience
Hematology/oncology fellows, attending faculty, and other health care professionals involved in the treatment of patients with mantle cell lymphoma (MCL).
Learning Objectives
1.) Identify clinical and biological prognostic factors that can guide treatment decision making for older adults with MCL
2.) Evaluate emerging data on targeted therapeutic approaches for treatment-naive and relapsed/refractory MCL and their applicability to older adults
3.) Assess mechanisms of resistance to targeted therapies for MCL and their implications for treatment selection
263778731218 Abortion Clinic /Pills In Harare ,sisternakatoto
263778731218 Abortion Clinic /Pills In Harare ,ABORTION WOMEN’S CLINIC +27730423979 IN women clinic we believe that every woman should be able to make choices in her pregnancy. Our job is to provide compassionate care, safety,affordable and confidential services. That’s why we have won the trust from all generations of women all over the world. we use non surgical method(Abortion pills) to terminate…Dr.LISA +27730423979women Clinic is committed to providing the highest quality of obstetrical and gynecological care to women of all ages. Our dedicated staff aim to treat each patient and her health concerns with compassion and respect.Our dedicated group ABORTION WOMEN’S CLINIC +27730423979 IN women clinic we believe that every woman should be able to make choices in her pregnancy. Our job is to provide compassionate care, safety,affordable and confidential services. That’s why we have won the trust from all generations of women all over the world. we use non surgical method(Abortion pills) to terminate…Dr.LISA +27730423979women Clinic is committed to providing the highest quality of obstetrical and gynecological care to women of all ages. Our dedicated staff aim to treat each patient and her health concerns with compassion and respect.Our dedicated group of receptionists, nurses, and physicians have worked together as a teamof receptionists, nurses, and physicians have worked together as a team wwww.lisywomensclinic.co.za/
HOT NEW PRODUCT! BIG SALES FAST SHIPPING NOW FROM CHINA!! EU KU DB BK substit...GL Anaacs
Contact us if you are interested:
Email / Skype : kefaya1771@gmail.com
Threema: PXHY5PDH
New BATCH Ku !!! MUCH IN DEMAND FAST SALE EVERY BATCH HAPPY GOOD EFFECT BIG BATCH !
Contact me on Threema or skype to start big business!!
Hot-sale products:
NEW HOT EUTYLONE WHITE CRYSTAL!!
5cl-adba precursor (semi finished )
5cl-adba raw materials
ADBB precursor (semi finished )
ADBB raw materials
APVP powder
5fadb/4f-adb
Jwh018 / Jwh210
Eutylone crystal
Protonitazene (hydrochloride) CAS: 119276-01-6
Flubrotizolam CAS: 57801-95-3
Metonitazene CAS: 14680-51-4
Payment terms: Western Union,MoneyGram,Bitcoin or USDT.
Deliver Time: Usually 7-15days
Shipping method: FedEx, TNT, DHL,UPS etc.Our deliveries are 100% safe, fast, reliable and discreet.
Samples will be sent for your evaluation!If you are interested in, please contact me, let's talk details.
We specializes in exporting high quality Research chemical, medical intermediate, Pharmaceutical chemicals and so on. Products are exported to USA, Canada, France, Korea, Japan,Russia, Southeast Asia and other countries.
1. Tamer Hifnawy MD. Dr.PH
Associate Professor
Public Health & Community Medicine
Faculty of Medicine – BSU- Egypt
College of Dentistry Taibah University- KSA
Vice Dean For Quality, Development & International Affairs
CertifiedTrainer for International Research Ethics
2. Study designs can be split into:
1. Observational: collect information on conditions the
investigator has no control.
2. Interventional (experimental): intervene to reduce
exposure or to allocate alternative treatments.
3.
4. Did the investigator assign exposures?
Yes No
Experimental study Observational study
Interventional Studies Comparison group?
Descriptive
study
Analytical
study
Direction?
Cross-sectional
study
Case-Control
study
Cohort
study
Yes No
Clinical Trials
11. A point in time picture of disease, health
event, medical or psychosocial phenomenon.
Most often utilizing a survey mechanism
Cross Sectional Study
12. They collect information to measure prevalence
at one point in time.
The prevalence of the outcome can be
measured without reference to exposure or the
reverse (descriptive).
The prevalence of disease can be measured in
relation to the exposure of interest (analytical).
14. No of cases of a disease diagnosed
during a cross-section study
------------------------------------ X 100
All examined individuals studied
15. Population
Representative
sample
(if not using
the whole pop)
Number with
Disease and
with
Exposure
Calculate
prevalence
of
disease, in
exposed.
Number with
Disease but
without
Exposure
Number without
Disease but
with
Exposure
Number without
Disease and
without
Exposure
Calculate
prevalence
of
disease, in
unexposed
TIME
16. Assume we are interested in the possible relationship
between serum cholesterol level (Exposure) and ECG
evidence of CHD (Outcome)
Information about exposure and disease is collected
simultaneously
17. Analysis of Cross-Sectional Studies
dc
Not
Exposed
baExposed
No DiseaseDisease
a / (a + b)
Prevalence Ratio (PR) = ------------
c / (c + d)
19. Cross-Sectional Studies
100 / (100 + 400) 0.2
Prevalence Ratio = --------------------- = ---- = 2.0
50 / (50 + 450) 0.1
Interpretation: In this study population, the
prevalence of CHD is 2 times higher among those
with high cholesterol, compared to the prevalence in
those with normal or low cholesterol.
20. Cross Sectional Study
Advantages
Less time
Less expensive
Ease
Provides vast information
Can study
interrelatedness of
variables
Not based on illness or
medical treatment
Disadvantages
Rarely able to establish
cause and effect
Bias to individuals who
complete the survey
Recurrent conditions not
picked up
21.
22. In language this means
“ A group united in some struggle”
Word Cohort is used in statistics to indicate
studying a group of different individuals with
some common features.
23. “ WHAT Will HAPPEN ? ”
Looking Forward in Time
30. A B
C D
Exposed
A+B
Not exposed
C+D
Cancer Cancer free
Relative Risk =
divided by
risk of cancer among
exposed group (A/A+B)
Risk of cancer among
unexposed (C/C+D)
31. Relative risks (RR) is a direct estimator of the exposure risk
When RR value is one then the risk of disease is the same in the
exposed and unexposed. This means that the studied exposure
factor is not a risk factor.
When RR value is more than one then the risk of disease in the
exposed group is greater than the risk in the unexposed group.
This means that the factor is a risk factor, or an etiological
factor for disease.
When RR is less than one then the risk of disease in the
exposed group is less than the risk in the unexposed. This means
that the factor is a protective factor.
32. A cohort study was done to determine the
association between vegetarianism and CHD.
Hypothetical results are presented in the
following table.
36. Cancer No Cancer Total
Exposed 10 100 110
Not Exposed 9 456 465
Relative risk = (A/A+B) / (C/C+D) = (10/110) / (9/465) = 4.79
37. PLUSES
Causality
Can cope with rare
exposures
Multiple outcomes can be
studied
Disease incidence is
measured
MINUSES
High costs
Long time period
Losses to follow-up
Residual confounding
38.
39.
40. This means collection of data for two different
groups of people.
The first group would be the group of
concern, that we need to collect data about, this
is known as cases groups.
The second group are people who are chosen for
comparison with the case group, this is known as
control group.
41. It is important to know that the control group
must be comparable to the case group, this is
called matching.
It is very difficult to match an individual to
another, because if he is of the same age, he may
not be of the same weight or height. Hence one
to one match is difficult, we usually get two or
three control individuals to each case person.
42. Another way is matching the whole case group
characteristics by a group of similar controls.
Accordingly, control group size should be at least
equal to the case group, of course it may be
double or triple the size of cases if two to one or
three to one matching is used.
52. 1. Start with finding subjects
cases
controls
2. Look back at risk factors
Back then today
time
Yes or No
53. A B
C D
Cases
Controls
Exposed Un-exposed
Exposure
Odds ratio =
divided by
odds of exposure
among the cases
(A/B)
odds of exposure
among the controls
(C/D)
54. Exposed Not exposed
Cases 119 317
Controls 68 319
Study of OC use and ovarian cancer risk
Odds ratio = (A/B) / (C/D) = (119/317) / (68/319) = 1.76
56. OR = 1.76 means that :
The odds of exposure to Oral
contraceptive among cases with ovarian
cancer is 1.76 times as large the odds of
exposure of OC among controls.
OC could be thus a Risk factor for
developingOvarian Cancer
57. Cannot compute directly relative risk
Not suitable for rare exposure
Relationship exposure-disease difficult to
establish (association not causality)
Biases +++
control selection
recall biases when collecting data
58. Rare diseases
Several exposures
Long latency
Rapidity
Low cost
Small sample size
Available data
No ethical problem