Public Health Final PDF

**Introduction** +-----------------------------------+-----------------------------------+ | **Epidemiology** | **Clinical Epidemiology** | +===================================+===================================+ | Is generally focused on | Is the application of...

**Introduction** +-----------------------------------+-----------------------------------+ | **Epidemiology** | **Clinical Epidemiology** | +===================================+===================================+ | Is generally focused on | Is the application of | | | | | occurrence **(distribution and** | **epidemiological principles | | | and** | | **determinants) of disease at** | | | | **methods to the clinical | | **the population level** | setting,** | | | | | Attempts to assess causes and | **for the purpose of improving** | | | | | **distribution of disease to** | **outcomes at the patient level** | | | | | **formulate statistical | Makes **scientifically-based** | | measures** | | | | **predictions by counting | | **of risk by counting | clinical** | | health-related events in people | | | in** | **observations/events (the 5 | | | Ds)** in | | relation to their groups | | | | relation to similar groups | +-----------------------------------+-----------------------------------+ **When clinical epidemiology is applied to the care of patients, it is termed** **"evidence-based medicine".** **Clinical epidemiology is foremost among the clinical sciences that is** **used by clinicians as a basic science tool in patient care.** **USEFULNESS OF CLINICAL MEDICINE** **Clinical epidemiology aims to:** ** answer clinical questions** and guide clinical decision making with the **best available evidence** ** make predictions a**bout individual patients by counting clinical events in groups of patients with similar illnesses, and **uses strong scientific** **methods t**o ensure that these predictions are accurate ** develop methods of clinical observation** and interpret those observations in order to come to **valid conclusions** of how best to care for patients, while avoiding systemic error and chance 1\. Clinical Questions about clinical issues 2\. Health Outcomes  3\. Variables- things that vary and be measured 4\. Numbers( events that can be counted or expressed as numbers) and Probability 5\. Populations and Samples 6\. Bias (Systemic Error) 7\. Chance 8\. The Cumulative Effects of Bias and Chance 9\. Validity Bias (Systemic Error) "A process or occurrence at any stage of inference that produces results that depart systematically from the true values." Three broad categories of bias in clinical observation: 1\. Selection bias 2\. Measurement bias 3\. Confounding bias **Abnormality** TYPES OF DATA Measurements of clinical phenomena yield three kinds of data: 1\. Nominal 2\. Ordinal 3\. Interval PERFORMANCE OF MEASUREMENTS Whatever the type of measurement, its performance can be described in several ways: Validity Reliability Range Responsiveness Interpretability **Criteria for abnormality** - - - **Frequency** Who is known as the father of epidemiology? John Snow What are the top two causes of death in Trinidad and Tobago? Heart Disease Diabetes Studies are likely to have three kinds of bias? What are they? Selection bias Measurement bias Confounding bias **Case** - - - - **Population** - - - DISTRIBUTION OF DISEASE - - - DISTRIBUTION OF DISEASE Major determinants are: 1\. Time( Endemic, epidemic, pandemic, sporadic, cluster) 2\. Place( cause and clue provider to its causes) 3\. Person( Clues to clauses and guidance on healthcare efforts) **Risk Vs Prognosis** - - - - TERMS USED TO DESCRIBE PROGNOSIS 1\. Clinical Course of Disease 2\. Natural History of disease ELEMENTS OF PROGNOSTIC STUDIES 1\. Sample 2\. Observations (zero-Time, inception cohort) 3\. follow up (enough time for the outcome to present itself) 4\. Outcome of a disease( Five D's) IDENTIFYING PROGNOSTIC FACTORS Survival of Cohorts Survival Analysis Survival Curves For this purpose, **outcome is described in terms of survival**. **Diagnosis** Factors affecting the accuracy of a test result - - - - - **Use of sensitive test**( helpful with a negative result) - - **Use of specific Tests( helpful when it is positive)** - - **Sensitivity and specificity in relation to test results** - - - **Treatment- anything intended to improve the course of disease** **Hypothesis-** ideas about what might be a useful treatment for any given illness , hypotheses are called assertions **Studies of Treatment effects( add table of advantages and disadvantages)** - - - **Elements of a control trial** - - - - - - - **Exclusion** - - - - - **Inclusion criteria** - - - Effectiveness Vs efficacy  **Limitations of randomized control trials** - - - - - - - - **Prevention- "the act of preventing or hindering" and "the act or practice of keeping something from happening "** There are four major types of clinical preventive care: 1. Immunization 2\. Screening 3\. Behavioural counselling(lifestyle changes) 4\. Chemoprevention LEVELS OF PREVENTION In clinical medicine, there are three levels of prevention: 1. Primary prevention(prevents disease from occurring) 2\. Secondary prevention (easy detection during asymptomatic) done in clinical setting 3\. Tertiary prevention( prevents deterioration in diseased symptomatic patients) M**ethods for deciding whether a proposed preventive activity should be undertaken** **(3 criteria for judging whether a condition should be included in preventive care):** 1\. Burdened suffering caused by the condition \(i) **Measuring Suffering:** mortality rates; frequency of hospitalizations; amount of health care utilization \(ii) **Frequency of a Condition:** A disease may cause great suffering, but may occur too rarely for screening to be considered. 2\. Effectiveness,safety, and cost of the preventive intervention or treatment (**Randomized controlled trials are the strongest scientific evidence for establishing the effectiveness of treatments)** 3\. Performance of the screening test a\. "HighSensitivityandSpecificity b\. HighPositivePredictiveValue c\. SimplicityandLowCost d\. Safety e\. Acceptable to Patients and Clinicians **CONCEPTS OF CAUSE** Consideration is given to three concepts of cause: 1\. Single and Multiple Causes Other Theories of Disease Causation 2\. Proximity of Cause to Effect(a search for the underlying pathogenetic mechanism of disease) 3\. Effect Modification +-------------+-------------+-------------+-------------+-------------+ | **Single | **Single | **Supernatu | **Ecologica | **Miasma | | and | and | ral | l | Theory** | | Multiple | Multiple | Theory / | Theory / | | | Causes** | Causes** | Divine | Environment | | | | | Interventio | ** | | | **Germ | **Multiple | n** | | | | Theory / | Cause | | | | | Single | Theory** | | | | | Cause | | | | | | Theory** | | | | | +=============+=============+=============+=============+=============+ | A one | Diseases | Diseases | Diseases | Diseases | | cause-one | caused by | caused by | caused by | caused by | | disease | multiple | either the | host-pathog | "bad air" | | relationshi | factors | curse of | en | | | p. | working | God or evil | interaction | 500 BC -- | | This theory | together, | force of | s | Miasmas are | | stipulates | which | demons | within the | poisonous | | that | differ in | | context of | emanations | | diseases | each | Punishment | their | from | | are | | for | | putrefying | | | case | mankind's | environment | carcasses, | | caused by | | sins | | | | microbes | Agent, | | Around 463 | vegetables, | | (germs): | host and | | BC, | molds and | | | environment | | Hippocrates | invisible | | | al | | advised to | particles | | | factors | | search the | | | | interact | | environment | This theory | | | synergistic | | for the | was used to | | | ally | | cause | explain | | | and act as | | | several | | | | | of disease | outbreaks | | | joint | | | of cholera, | | | independent | | | plague and | | | partners in | | | | | | causing | | | malaria\* | | | disease | | | | | | | | | \*mal = | | | e.g. | | | bad; aria = | | | Coronary | | | air | | | artery | | | | | | disease has | | | | | | multiple | | | | | | causes | | | | | | including: | | | | | | cigarette | | | | | | | | | | | | smoking, | | | | | | hypertensio | | | | | | n, | | | | | | diabetes, | | | | | | hypercholes | | | | | | terolemia, | | | | | | inflammatio | | | | | | n | | | | | | and | | | | | | | | | | | | heredity. | | | | | | | | | | | | Note: | | | | | | While the | | | | | | presence of | | | | | | the | | | | | | organism is | | | | | | a necessary | | | | | | cause for | | | | | | disease to | | | | | | occur, | | | | | | | | | | | | it may not | | | | | | be | | | | | | necessarily | | | | | | a | | | | | | sufficient | | | | | | cause (e.g. | | | | | | AIDS cannot | | | | | | occur | | | | | | without | | | | | | | | | | | | exposure to | | | | | | HIV, but | | | | | | exposure to | | | | | | HIV does | | | | | | not | | | | | | necessarily | | | | | | result in | | | | | | AIDS) | | | | +-------------+-------------+-------------+-------------+-------------+ **Two ways of establishing cause**: 1\. Association ( does not prove cause) 2\. Strength of Research Design (randomized controlled trial) "BRADFORD HILL CRITERIA" 1\. Temporal relationships between cause and effect 2\. Strength of association 3\. Dose-response relationships 4\. Reversible associations 5\. Consistency 6\. Biological plausibility 7\. Specificity 8\. Analogy COHORT STUDIES Criteria for observations of members in Cohort Studies: 1\. They **do not have the disease (or outcome)** in question at the time they are assembled. 2\. They should be **observed over a meaningful period of time** in the natural history of the disease in question so that there will be sufficient time for the risk to be expressed. 3\. All members **should be observed over the full period** **of follow-up,** or methods must be used to account for dropouts. Types of Cohort Studies: 1\. Prospective Cohort Study Present to Future +-----------------------------------+-----------------------------------+ | **Pros** | **Cons** | +===================================+===================================+ | Can assess purported risk factors | Can be time-consuming and | | not usually captured in medical | expensive | | records | | | | Not ideal for rare or long | | (including health behaviours , | latency diseases | | educational level, socioeconomic | | | status | | | | | | etc.) | | | | | | Researchers can be prepared to | | | collect information about | | | possible | | | | | | confounders. | | | | | | All the information can be | | | collected in a standardized | | | manner that | | | | | | decreases measurement bias | | +-----------------------------------+-----------------------------------+ 2\. Retrospective / Historical Cohort Study Past to Present +-----------------------------------+-----------------------------------+ | **Pros** | **Cons** | +===================================+===================================+ | Pros: | Cons: | | | | | Can take advantage of | Does not usually include | | computerised medical databases | factors omitted from computerised | | and population | databases | | | | | registries | (such as patients' lifestyle, | | | social status, education, and | | Take less time, are less | other important | | expensive, and are much easier to | | | do | health determinants) | | | | | | Information in many databases, | | | especially medical care | | | information, is | | | | | | not collected in a standardised | | | manner, leading to the | | | possibility of bias | | | | | | in results | +-----------------------------------+-----------------------------------+ **Risk- Exposure to Disease** Obtaining estimates of risk Experiments are not always possible or ethical, so the effects of most risk factors in humans cannot be studied with experimental studies. In these cases, **observational studies are used.** Clinical studies in which the researcher gathers data by simply observing events as they happen, without playing an active part in what takes place. Most studies of risk are observational studies and are either **Cohort Studies or** **Case-Control Studies**  **Cohort also called Incidence, prospective and longitudinal**  **CASE-CONTROL STUDIES** **The validity of case-control studies depends on:** 1\. The care with which cases and controls are selected 2\. Comparability of cases and controls 3\. How exposure is measured 4\. How extraneous variables are controlled  **RISK COMMUNICATION** Refers to how effectively clinicians communicate risk to patients **Importance of Risk communication** People weigh risk based on whether they or someone close to them experienced the outcome. Risk seems larger when the experience with it is recent or especially Memorable. **Ways of describing risk** Quantitative terms and actual frequencies e.g. " 1 per 14,000 persons develop cancer after being exposed to asbestos" Pictures (graphs, charts) may communicate more effectively than numbers