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
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 ...
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 ...
The case study approach allows in-depth, multi-faceted explorations of complex issues in their real-life settings. The value of the case study approach is well recognised in the fields of business, law and policy, but somewhat less so in health services research. Based on our experiences of conducting several health-related case studies, we reflect on the different types of case study design, the specific research questions this approach can help answer, the data sources that tend to be used, and the particular advantages and disadvantages of employing this methodological approach.
The case study approach allows in-depth, multi-faceted explorations of complex issues in their real-life settings. The value of the case study approach is well recognised in the fields of business, law and policy, but somewhat less so in health services research. Based on our experiences of conducting several health-related case studies, we reflect on the different types of case study design, the specific research questions this approach can help answer, the data sources that tend to be used, and the particular advantages and disadvantages of employing this methodological approach.
The prostate is an exocrine gland of the male mammalian reproductive system
It is a walnut-sized gland that forms part of the male reproductive system and is located in front of the rectum and just below the urinary bladder
Function is to store and secrete a clear, slightly alkaline fluid that constitutes 10-30% of the volume of the seminal fluid that along with the spermatozoa, constitutes semen
A healthy human prostate measures (4cm-vertical, by 3cm-horizontal, 2cm ant-post ).
It surrounds the urethra just below the urinary bladder. It has anterior, median, posterior and two lateral lobes
It’s work is regulated by androgens which are responsible for male sex characteristics
Generalised disease of the prostate due to hormonal derangement which leads to non malignant enlargement of the gland (increase in the number of epithelial cells and stromal tissue)to cause compression of the urethra leading to symptoms (LUTS
Title: Sense of Taste
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 structure and function of taste buds.
Describe the relationship between the taste threshold and taste index of common substances.
Explain the chemical basis and signal transduction of taste perception for each type of primary taste sensation.
Recognize different abnormalities of taste perception and their causes.
Key Topics:
Significance of Taste Sensation:
Differentiation between pleasant and harmful food
Influence on behavior
Selection of food based on metabolic needs
Receptors of Taste:
Taste buds on the tongue
Influence of sense of smell, texture of food, and pain stimulation (e.g., by pepper)
Primary and Secondary Taste Sensations:
Primary taste sensations: Sweet, Sour, Salty, Bitter, Umami
Chemical basis and signal transduction mechanisms for each taste
Taste Threshold and Index:
Taste threshold values for Sweet (sucrose), Salty (NaCl), Sour (HCl), and Bitter (Quinine)
Taste index relationship: Inversely proportional to taste threshold
Taste Blindness:
Inability to taste certain substances, particularly thiourea compounds
Example: Phenylthiocarbamide
Structure and Function of Taste Buds:
Composition: Epithelial cells, Sustentacular/Supporting cells, Taste cells, Basal cells
Features: Taste pores, Taste hairs/microvilli, and Taste nerve fibers
Location of Taste Buds:
Found in papillae of the tongue (Fungiform, Circumvallate, Foliate)
Also present on the palate, tonsillar pillars, epiglottis, and proximal esophagus
Mechanism of Taste Stimulation:
Interaction of taste substances with receptors on microvilli
Signal transduction pathways for Umami, Sweet, Bitter, Sour, and Salty tastes
Taste Sensitivity and Adaptation:
Decrease in sensitivity with age
Rapid adaptation of taste sensation
Role of Saliva in Taste:
Dissolution of tastants to reach receptors
Washing away the stimulus
Taste Preferences and Aversions:
Mechanisms behind taste preference and aversion
Influence of receptors and neural pathways
Impact of Sensory Nerve Damage:
Degeneration of taste buds if the sensory nerve fiber is cut
Abnormalities of Taste Detection:
Conditions: Ageusia, Hypogeusia, Dysgeusia (parageusia)
Causes: Nerve damage, neurological disorders, infections, poor oral hygiene, adverse drug effects, deficiencies, aging, tobacco use, altered neurotransmitter levels
Neurotransmitters and Taste Threshold:
Effects of serotonin (5-HT) and norepinephrine (NE) on taste sensitivity
Supertasters:
25% of the population with heightened sensitivity to taste, especially bitterness
Increased number of fungiform papillae
Knee anatomy and clinical tests 2024.pdfvimalpl1234
This includes all relevant anatomy and clinical tests compiled from standard textbooks, Campbell,netter etc..It is comprehensive and best suited for orthopaedicians and orthopaedic residents.
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
Recomendações da OMS sobre cuidados maternos e neonatais para uma experiência pós-natal positiva.
Em consonância com os ODS – Objetivos do Desenvolvimento Sustentável e a Estratégia Global para a Saúde das Mulheres, Crianças e Adolescentes, e aplicando uma abordagem baseada nos direitos humanos, os esforços de cuidados pós-natais devem expandir-se para além da cobertura e da simples sobrevivência, de modo a incluir cuidados de qualidade.
Estas diretrizes visam melhorar a qualidade dos cuidados pós-natais essenciais e de rotina prestados às mulheres e aos recém-nascidos, com o objetivo final de melhorar a saúde e o bem-estar materno e neonatal.
Uma “experiência pós-natal positiva” é um resultado importante para todas as mulheres que dão à luz e para os seus recém-nascidos, estabelecendo as bases para a melhoria da saúde e do bem-estar a curto e longo prazo. Uma experiência pós-natal positiva é definida como aquela em que as mulheres, pessoas que gestam, os recém-nascidos, os casais, os pais, os cuidadores e as famílias recebem informação consistente, garantia e apoio de profissionais de saúde motivados; e onde um sistema de saúde flexível e com recursos reconheça as necessidades das mulheres e dos bebês e respeite o seu contexto cultural.
Estas diretrizes consolidadas apresentam algumas recomendações novas e já bem fundamentadas sobre cuidados pós-natais de rotina para mulheres e neonatos que recebem cuidados no pós-parto em unidades de saúde ou na comunidade, independentemente dos recursos disponíveis.
É fornecido um conjunto abrangente de recomendações para cuidados durante o período puerperal, com ênfase nos cuidados essenciais que todas as mulheres e recém-nascidos devem receber, e com a devida atenção à qualidade dos cuidados; isto é, a entrega e a experiência do cuidado recebido. Estas diretrizes atualizam e ampliam as recomendações da OMS de 2014 sobre cuidados pós-natais da mãe e do recém-nascido e complementam as atuais diretrizes da OMS sobre a gestão de complicações pós-natais.
O estabelecimento da amamentação e o manejo das principais intercorrências é contemplada.
Recomendamos muito.
Vamos discutir essas recomendações no nosso curso de pós-graduação em Aleitamento no Instituto Ciclos.
Esta publicação só está disponível em inglês até o momento.
Prof. Marcus Renato de Carvalho
www.agostodourado.com
Couples presenting to the infertility clinic- Do they really have infertility...Sujoy Dasgupta
Dr Sujoy Dasgupta presented the study on "Couples presenting to the infertility clinic- Do they really have infertility? – The unexplored stories of non-consummation" in the 13th Congress of the Asia Pacific Initiative on Reproduction (ASPIRE 2024) at Manila on 24 May, 2024.
Report Back from SGO 2024: What’s the Latest in Cervical Cancer?bkling
Are you curious about what’s new in cervical cancer research or unsure what the findings mean? Join Dr. Emily Ko, a gynecologic oncologist at Penn Medicine, to learn about the latest updates from the Society of Gynecologic Oncology (SGO) 2024 Annual Meeting on Women’s Cancer. Dr. Ko will discuss what the research presented at the conference means for you and answer your questions about the new developments.
NVBDCP.pptx Nation vector borne disease control programSapna Thakur
NVBDCP was launched in 2003-2004 . Vector-Borne Disease: Disease that results from an infection transmitted to humans and other animals by blood-feeding arthropods, such as mosquitoes, ticks, and fleas. Examples of vector-borne diseases include Dengue fever, West Nile Virus, Lyme disease, and malaria.
Acute scrotum is a general term referring to an emergency condition affecting the contents or the wall of the scrotum.
There are a number of conditions that present acutely, predominantly with pain and/or swelling
A careful and detailed history and examination, and in some cases, investigations allow differentiation between these diagnoses. A prompt diagnosis is essential as the patient may require urgent surgical intervention
Testicular torsion refers to twisting of the spermatic cord, causing ischaemia of the testicle.
Testicular torsion results from inadequate fixation of the testis to the tunica vaginalis producing ischemia from reduced arterial inflow and venous outflow obstruction.
The prevalence of testicular torsion in adult patients hospitalized with acute scrotal pain is approximately 25 to 50 percent
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.
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!
These simplified slides by Dr. Sidra Arshad present an overview of the non-respiratory functions of the respiratory tract.
Learning objectives:
1. Enlist the non-respiratory functions of the respiratory tract
2. Briefly explain how these functions are carried out
3. Discuss the significance of dead space
4. Differentiate between minute ventilation and alveolar ventilation
5. Describe the cough and sneeze reflexes
Study Resources:
1. Chapter 39, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 34, Ganong’s Review of Medical Physiology, 26th edition
3. Chapter 17, Human Physiology by Lauralee Sherwood, 9th edition
4. Non-respiratory functions of the lungs https://academic.oup.com/bjaed/article/13/3/98/278874
Lung Cancer: Artificial Intelligence, Synergetics, Complex System Analysis, S...Oleg Kshivets
RESULTS: Overall life span (LS) was 2252.1±1742.5 days and cumulative 5-year survival (5YS) reached 73.2%, 10 years – 64.8%, 20 years – 42.5%. 513 LCP lived more than 5 years (LS=3124.6±1525.6 days), 148 LCP – more than 10 years (LS=5054.4±1504.1 days).199 LCP died because of LC (LS=562.7±374.5 days). 5YS of LCP after bi/lobectomies was significantly superior in comparison with LCP after pneumonectomies (78.1% vs.63.7%, P=0.00001 by log-rank test). AT significantly improved 5YS (66.3% vs. 34.8%) (P=0.00000 by log-rank test) only for LCP with N1-2. Cox modeling displayed that 5YS of LCP significantly depended on: phase transition (PT) early-invasive LC in terms of synergetics, PT N0—N12, cell ratio factors (ratio between cancer cells- CC and blood cells subpopulations), G1-3, histology, glucose, AT, blood cell circuit, prothrombin index, heparin tolerance, recalcification time (P=0.000-0.038). Neural networks, genetic algorithm selection and bootstrap simulation revealed relationships between 5YS and PT early-invasive LC (rank=1), PT N0—N12 (rank=2), thrombocytes/CC (3), erythrocytes/CC (4), eosinophils/CC (5), healthy cells/CC (6), lymphocytes/CC (7), segmented neutrophils/CC (8), stick neutrophils/CC (9), monocytes/CC (10); leucocytes/CC (11). Correct prediction of 5YS was 100% by neural networks computing (area under ROC curve=1.0; error=0.0).
CONCLUSIONS: 5YS of LCP after radical procedures significantly depended on: 1) PT early-invasive cancer; 2) PT N0--N12; 3) cell ratio factors; 4) blood cell circuit; 5) biochemical factors; 6) hemostasis system; 7) AT; 8) LC characteristics; 9) LC cell dynamics; 10) surgery type: lobectomy/pneumonectomy; 11) anthropometric data. Optimal diagnosis and treatment strategies for LC are: 1) screening and early detection of LC; 2) availability of experienced thoracic surgeons because of complexity of radical procedures; 3) aggressive en block surgery and adequate lymph node dissection for completeness; 4) precise prediction; 5) adjuvant chemoimmunoradiotherapy for LCP with unfavorable prognosis.
2. Observational studies are research studies in
which researchers collect information from
participants or look at data that was already
collected.
In observational studies, researchers follow
groups of people over a period of time.
Depending on the study, groups may include
healthy people, people with cancer, or people
who are at high risk for developing cancer, such
as those with a family history.
4. DESCRIPTIVE STUDIES
Descriptive studies generally describe the magnitude of a problem and
characteristics of the population/individuals.
The various types of such studies include
1. case reports
2. 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.
5. ANALYTICAL STUDIES
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 –
1. cross-sectional,
2. case control (also known as retrospective) and
3. 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 or incidence), cause of
disease, prognosis, or effect of treatment/intervention.
Each of the study designs should mention the details of
participant, exposure and comparison/control group (as
applicable), outcome to be analyzed and time as per the
PICOT format clearly in the protocol.
6. The word PICOT is a mnemonic derived from the elements
of a clinical research question – patient, intervention,
comparison, outcome and (sometimes) time. The PICOT
process begins with a case scenario, and the question is
phrased to elicit an answer.
It was developed by Physicians as an evidence based
practice model as a way to consolidate any gaps in
knowledge with patient interactions. As mentioned below,
these would address factors such as diagnosis, prognosis,
therapy, prevention strategies, and patient education.
A PICOT question helps you,
form a question which focuses on an important issue for a
patient or population
Identify important terms to use while searching for
evidence
Filter for and select results directly related to your topic of
8. Incidence (new events) can be determined from
cohort studies and prevalence (old plus new
events) from cross sectional studies.
Cause/etiology can be ascertained from cohort,
case control or cross-sectional studies where
there are two or more comparison groups (in their
decreasing order of reliability). Prognosis can be
provided by cohort studies that prospectively
measure outcome.
However, effect of treatment cannot be reliably
obtained from observational studies and would
need a controlled clinical trial (experimental
design).
9. The PICOT question can fall under these
categories:
Therapy/Prevention
Diagnosis
Etiology
Prognosis
10. P represents Population/Patient/Problem [3] - this would
indicate the type of person or population of people that you
want to research about. Here, you can note their
characteristics, and any health conditions that might be
present, any health goals, or any other qualities.
I represents Intervention - this would be the treatment,
conditions, or changing factor present in the question you
are creating.
C represents Comparison - this would be the group you
want to compare to, generally the control group, who
receives no treatment, a general standard treatment, or a
'gold-standard' treatment.
O represents Outcome - this is the result or outcome that
you would like measured in your research question. This
would indicate the result of the intervention in your
question.
T, is an optional component of PICOT which
represents Time - the period, or duration of effect, that is a
part of your research question.
11.
12. Example 1
Scenario: You have a female patient who has recently
been diagnosed with SLE. Her rheumatologist
suggested she start on Plaquenil for her joint pain, but
she is interested in alternative therapies because she
heard about success a neighbor had with turmeric tea.
P- patients with SLE
I- turmeric tea
C- Plaquenil (standard drug therapy)
O- reduction of joint pain
Question: In adult patients with SLE, is consuming
turmeric tea more effective than Plaquenil at reducing
joint pain?
This question could be more specific (Gender specific?
What counts as a reduction in joint pain?), but is still a
therapy question. We're comparing an alternative therapy
(turmeric tea) with a more standard drug therapy
(Plaquenil).
13. Example 2
Scenario: Your patient has a history of blood clots
and after they came in to your clinic with right calf
discomfort and tightness, you're concerned about
DVT. You remember reading about the limitations of
duplex ultrasound and calfveins, and are wondering if
a d-dimer assay can help you rule out DVT more
accurately.
P- adults
I- d-dimer assay
C- ultrasound
O- more accurate diagnosis of DVT
Question: Is d‐dimer assay more accurate at
ruling out deep vein thrombosis compared to
ultrasound?
14. Cross-Sectional Studies
Cross-sectional studies provide a snapshot of
both the exposure (or risk factor) and the
outcome in the sample. Here the information on
exposure and outcome are noted at the same
time.
They are generally descriptive and provide
information on prevalence (the number of cases
in a population at a given point/period).
However, cross sectional studies can also be
analytical where the strength of association
between two variables can be estimated and is
reported as an odds ratio (OR), which can be
useful for hypothesis generation
15. Conducting Cross-Sectional
Studies
The first step would be to formulate a research
question. The next step is to identify the target
population to whom the results would be generalized
and then select a study sample as per the logistic
considerations.
The sampling strategy could be simple random,
stratified (e.g., age and gender where outcomes are
dependent on these variables), systematic (especially
in hospital-based studies), multistage (e.g., districts,
villages, households) or cluster sampling (the last two
sampling methods are useful
when large populations are to be included in the
study).
Lastly, the variables relevant to the research question
must be identified during the study planning stage.
16. Advantages and
Disadvantages
Cross-sectional studies are useful when one
wishes to gather information rapidly and in an
inexpensive way.
It can provide descriptive data and can also
determine an association between two or more
groups.
Another advantage is that multiple outcomes can
be studied. However, cross-sectional studies
cannot assess risk but can provide information on
association.
They would also not be an appropriate choice
where one or more of the variables of interest are
rare.
They do not provide reliable information on
17. Example:
A study in Ethiopia aimed to
determine the prevalence
and associated factors of
malaria in under-five
children. This was a facility-
based cross-sectional study
conducted among 585
under-five children who
attended public health
facilities. Health facilities
were selected by stratified
cluster sampling, and
systematic random sampling
was done to select study
participants from the
selected facilities. Malaria
was defined as a positive
thin or thick blood film for the
Plasmodium parasite. It was
observed that 51 (8.7%)
Comment:
In this example, the study
was conducted across
multiple hospitals (hence
cluster sampling was used)
and systematic random
sampling was used to select
participants within each
health facility. The research
question required estimation
of point prevalence of
malaria as per a predefined
diagnostic criterion.
18. Case-Control Studies
Case-control studies are retrospective in nature. Subjects are
enrolled based on “presence (cases)” or “absence (controls)” of
outcome (or disease). Information related to potential risk factors
is collected by the investigator after the outcome has occurred.
As the direction of enquiry is from outcome to exposure, hence is
termed as a retrospective study.
Conducting Case-Control Studies
As for all studies a research question must be formulated.
Unlike cross sectional studies, case-control studies would
require an apriori hypothesis and hence one must decide what
must be measured and how.
The next step is to choose the case and control group with valid
and precise definitions.
The definition of a case should be objective (e.g., diagnostic
criteria of a disease or event) such that there is no ambiguity in
type of cases and/or their severity. Cases can be hospital-based
or population-based. Defining control is equally important and
critical to the outcome of case-control studies.
19. Every effort must be made to ensure absence of outcome
in controls. The controls should represent the population
from where the cases have been selected and need not
always be healthy.
they should be equally predisposed to develop the
outcome under study and are selected from the same
source population as the cases.
They can be selected from friends, relatives or from the
neighbourhood as this can be done with minimum effort.
Such controls, however, have the risk of being very similar
with respect to exposures and other characteristics (can be
overmatched).
On the other hand, selecting an appropriate hospital
control can be challenging and care must be taken to
prevent selection bias.
Use of two or more controls increases reliability (e.g.,
outpatients, inpatients, from general practice, etc.).
Selecting an appropriate control is one of the most
20. The exposure of interest is considered ‘a risk
factor’ and its association with the outcome is
reported as odds ratio (OR) (or as adjusted OR
after confounder control).
The odds ratio from case control studies informs
one as to how much higher the odds of exposure
are among casepatients than among controls (or
if it is associated with reduced risk, it would inform
about how much lower is the odds of exposure
among case-patients than among control).
For rare diseases, such as cancer, the odds ratio
is likely to approximate relative risk values
obtained from prospective (cohort) studies
21. Nested case-control study
This is a variant of a case-control study in which the
cases and controls are drawn from a pre-existing
cohort study.
For every defined case in the cohort a matched
control from the cohort is selected. They are
particularly useful for studying the biological
precursors of disease.
The advantage of this design is that it minimizes
selection, recall bias and measurement bias (as the
variables have been pre-defined and collected
concurrently in a standardized manner having been
part of a cohort study) in comparison to case-controls
studies, and is faster and less expensive than a
22. Advantages and Disadvantages
Case control studies are relatively simple to perform
and provide results over a relatively shorter time than
cohort studies and require lesser resources. They
provide information about predictors of an outcome.
The problem of confounding can be overcome using
matched controls for a few of the important selected
confounding characteristics.
The disadvantages are that they cannot provide
information on incidence or prevalence and can look
at only one outcome. They are also more prone to
bias, particularly selection, observation, recall and
measurement bias. Selection bias could be minimized
by use of matched or population-based controls.
Recall bias could be minimized by using recorded
data before the occurrence of the outcome being
studied. Because of the risks of confounding and bias,
case control studies are less reliable for ascertaining
causality but can help in hypothesis generation
23. Example of a Case-Control Study
Example:
This study attempted to identify the characteristics of malnourished
children below five years of age and the risk factors of childhood
malnutrition. It hypothesized that risk of childhood malnutrition
(outcome) was increased in poor households (exposure).
Case was a child with moderate to severe malnutrition (z-scores <-2SD
from the median of WHO reference of any anthropometry - weight,
length/height, weight/length).
Control was a child with zscores between -2SD and +2SD and was age
matched with the cases.
The participants were identified from those attending the maternal-child
health clinics.
The study identified the variables/exposures that could affect nutrition
from three domains-socio-economic characteristics, household food
security and child’s dietary intake, and caregiver practices and
resources.
The study clearly defined how the above measures were to be
collected. There were 137 cases and 137 controls. T
he study identified the following as significant risk factors for childhood
malnutrition – Household poverty
24. Cohort Studies
Cohort studies (or longitudinal studies) are
generally prospective but can also be
retrospective. However, unless qualified, the term
cohort studies imply prospective cohort studies.
Cohort studies are the designs of choice for
determining incidence and natural course of a
disease. The association of risk factors with
outcome is generally reported as relative risk
(RR) or attributable risk.
25. Prospective Cohort Studies
In prospective cohort studies, the participants are a group
of individuals in whom the outcome of interest (e.g., lung
cancer) has not occurred at the time of selection into the
study.
The investigator identifies all possible relevant variables
that may contribute to the development of the outcome and
measures them accurately in the participants during follow-
up.
The participants during follow-up are carefully followed up
and observed to see if they develop the outcome of
interest.
The steps in a prospective cohort are as follows: i) identify
a research hypothesis, ii) define objectively the exposure
(risk factors) and outcomes, iii) develop a standard data
collection tool (to minimize information bias), iv) identify
steps during follow-up to minimize the drop outs (selection
bias), and v) define the analysis plan to measure the
26. a. Descriptive Cohort:
A descriptive cohort study describes outcome over time for a
specific group of individuals, without any comparison of groups.
Examples are patients with a defined type of cancer(s) who are
followed up to describe the epidemiology of the disease.
b. Single analytic cohort:
In such a study, those who develop the outcome of interest are
treated as ‘cases’ and those who do not develop the outcome of
interest are treated as ‘controls’ (also known as internal controls).
The investigator may also opt for an external control when
internal controls are not available (when exposure cannot not be
verified/ was not measured).
Two group analytic cohort.
When there are two cohorts being followed, one of the groups
would have been exposed to the variable of interest while the
other would not. Both groups would be followed to observe for
the occurrence of the outcome of interest. Here those without
exposure to the variable of interest would serve as the
comparison/control group (external controls).
27. Retrospective Cohort Study
This is a type of cohort study where the
investigator looks back retrospectively at already
collected data (prospectively) after the outcome
of interest has occurred i.e., posthoc.
The important distinguishing feature of
retrospective from prospective cohort study is that
the investigator comes up with the idea of the
study and begins to identify variables and
subjects after the outcome of interest has
occurred.
An ambispective cohort study design allows the
researcher to retrospectively measure the
exposure in a cohort and follow them
prospectively for a disease outcome.
28. Advantages and Disadvantages
Cohort studies
Advantages and Disadvantages Cohort studies are the
choice where randomized control trials would be
considered unethical e.g., effect of smoking on lung
cancer.
As the design affords a temporal sequence, it is a very
good method to establish cause and effect (hence allows
one to measure incidence) and analyze risk factors or
predictors (allows to measure relative and attributable
risk).
They also have the advantage of being able to measure
multiple outcomes from a single study
e.g., effect of breast-feeding duration on child growth,
obesity, diarrhea, and acute illnesses or even multiple
exposures e.g., effect of multiple environmental exposures
to child health outcomes .
The disadvantages could include loss of subjects (loss of
cases becomes more important as it can alter incidence
rates) during the follow-up, confounding and
nonrepresentative nature of the cohort sample (selection
29. References
Ramji S. Study Design: Observational Studies. Indian
Pediatrics. 2022 Jun;59(6):493-8.
https://guides.hsl.virginia.edu/c.php?g=921177&p=663862
3
Khan AM, Gupta P, Mishra D. The 3-question approach: a
simplified framework for selecting study designs. Indian
Pediatr. 2019;56:669-72.
Indrayan A. Medical Statistics,3rd edn. Boca Raton, CRC
Press, Taylor and Francis Group, 2013; 83-110.
Tsegaye AT, Ayele A, Birhanu S. Prevalence and
associated factors of malaria in children under the age of
five years in Wogera district, northwest Ethiopia: A
crosssectional study. PloS One. 2021;16:e0257944.
Case control and cross-sectional studies. In: Coggon D,
Rose G, Barker DJP, editors. Epidemiology for the
Uninitiated, 5th ed. BMJ publishing group, 2003.