Epidemiology

Epidemiology Indian Medical PG Question 1: What is the first step an epidemiologist takes in an epidemic investigation?

• A. Confirm the diagnosis (Correct Answer)
• B. Identify the prone people
• C. Identify the causative factors
• D. Identify the cases

Epidemiology Explanation: ***Confirm the diagnosis*** - The initial and most crucial step is to **confirm the diagnosis** of the disease in question to ensure that the reported cases are indeed suffering from the same condition. - This step helps to avoid misclassification and ensures the investigation focuses on a specific, confirmed health problem. *Identify the cases* - While essential, **identifying cases** usually follows initial diagnostic confirmation, as you need a clear case definition based on a confirmed diagnosis to correctly identify who is a case. - This involves defining who is considered a case based on symptoms, laboratory results, and epidemiological links. *Identify the prone people* - **Identifying prone people** refers to determining the population at risk, which is a subsequent step after understanding the confirmed disease and its initial pattern. - This step typically falls under characterizing the distribution of the disease (person, place, time) in the investigation. *Identify the causative factors* - **Identifying causative factors** is a later stage in the investigation, often involving analytical studies to test hypotheses, which can only occur effectively once the diagnosis is confirmed and cases are clearly defined and counted. - This step aims to understand *why* the epidemic is occurring, after establishing *what* is occurring.

Epidemiology Indian Medical PG Question 2: Which of the following are the components of epidemiological triad?

• A. Sensitivity, specificity and predictive value
• B. Prevalence, incidence and attack rate
• C. Time, place and person distribution
• D. Agent, host and environmental factors (Correct Answer)

Epidemiology Explanation: ***Agent, host and environmental factors*** - The **epidemiological triad** is a traditional model that explains disease causation by focusing on the interaction between an infectious **agent**, a susceptible **host**, and the **environment** that brings them together. - Understanding these three components helps to analyze and prevent the spread of diseases. *Sensitivity, specificity and predictive value* - These terms relate to the **performance and accuracy of diagnostic tests**, assessing how well a test identifies true positives and true negatives. - They are measures used in the evaluation of screening programs and diagnostic procedures, not directly in the causation model. *Prevalence, incidence and attack rate* - These are **measures of disease occurrence** or frequency within a population, used to quantify the burden of disease. - While essential for understanding disease patterns, they describe the *results* of the disease process rather than the *factors* causing it. *Time, place and person distribution* - These refer to the **descriptive epidemiology** aspects of disease, outlining **who** is affected, **where** they are, and **when** the disease occurs. - These elements characterize disease patterns but are not the fundamental components responsible for disease causation in the epidemiological triad model.

Epidemiology Indian Medical PG Question 3: Berksonian bias is a type of ?

• A. Selection bias (Correct Answer)
• B. Information bias
• C. Interviewer bias
• D. Recall bias

Epidemiology Explanation: ***Selection bias*** - **Berkson's bias** is a form of **selection bias** that arises in studies conducted using hospital data. - It occurs when the probability of admission to a hospital or inclusion in a study is conditional on both exposure and disease status, leading to a **flawed association** between them. *Interviewer bias* - **Interviewer bias** is a type of **information bias** where the interviewer's expectations or knowledge about the study or participants influence the way information is sought or recorded. - This typically affects the **data collection process** and not the selection of participants. *Information bias* - **Information bias** is a broad category of biases that arise from **systematic errors in measurement** or classification of exposure or disease. - While Berkson's bias can lead to misinformation, its root cause is in how subjects are selected, not how data on those subjects is collected after selection. *Recall bias* - **Recall bias** is a type of **information bias** where there are systematic differences in the way participants **recall past events or exposures**. - It is particularly common in **case-control studies** where individuals with a disease may remember exposures differently than healthy controls.

Epidemiology Indian Medical PG Question 4: Which of the following best describes the concept where a suspected cause precedes the observed effect?

• A. Temporal association (Correct Answer)
• B. Consistency of association
• C. Strength of association
• D. Coherence of association

Epidemiology Explanation: ***Temporal association*** - This principle in **causal inference** emphasizes that for a factor to be a cause, it must precede the effect. - In epidemiology, it's crucial to establish that exposure occurred **before the disease manifestation**. *Consistency of association* - Refers to the observation of a **similar association across different studies** and populations. - While important for causal inference, it does not directly address the timing of cause and effect. *Strength of association* - Quantifies how often the **exposure and outcome co-occur**, often measured by relative risk or odds ratio. - A strong association is more likely to be causal, but it doesn't confirm that the cause came before the effect. *Coherence of association* - Implies that the observed association should be **consistent with existing biological and medical knowledge**. - This criterion supports the plausibility of an association but doesn't specifically deal with the temporal sequence.

Epidemiology Indian Medical PG Question 5: Which one of the following is FALSE regarding confounding factor in epidemiological studies ?

• A. Source of bias is interpretation
• B. Associated both with exposure and disease
• C. Independent risk factor for disease in question
• D. Distributed equally between study and control groups (Correct Answer)

Epidemiology Explanation: ***Distributed equally between study and control groups*** - A **confounding factor** is, by definition, **not equally distributed** between study (exposed) and control (unexposed) groups, as this unequal distribution leads to the observed bias. - If a potential confounder were equally distributed, it would not distort the relationship between the exposure and the outcome. *Source of bias is interpretation* - Confounding is a source of **bias in interpretation** because it can create a spurious association or mask a true one between an exposure and an outcome. - It leads to an incorrect conclusion about the causal relationship, even if the data collection itself was accurate. *Associated both with exposure and disease* - For a variable to be a confounder, it must be **associated with the exposure** being studied (e.g., smoking is associated with alcohol consumption). - It must also be an **independent risk factor for the disease** outcome (e.g., alcohol consumption is an independent risk factor for esophageal cancer). *Independent risk factor for disease in question* - A confounder must be an **independent risk factor** for the disease outcome, separate from its association with the primary exposure. - This means it influences the disease risk regardless of the exposure being investigated.

Epidemiology Flashcard 1 of 5

Question: A _____ case-control study is essentially a case-control study that is present inside a cohort study.

Answer: nested

Epidemiology Flashcard 2 of 5

Question: Incidence and prevalence rates are included in _____ indicators

Answer: morbidity (mortality/morbidity)

Epidemiology Flashcard 3 of 5

Question: An incidence rate is a special type of proportion that includes a given _____ and a population at risk

Answer: time range

Epidemiology Flashcard 4 of 5

Question: IDR = (_____)/(sum of time periods for all disease free individuals at risk)

Answer: # of new cases

Epidemiology Flashcard 5 of 5

Question: Confounding Bias can be reduced by RANDOMIZATION, but other important interventions include:- _____ of exposure groups- crossover studies- restriction of characteristics- multiple / repeated studies

Answer: Matching / Stratification