Anglais médical · p2

Identifying bias and confounding in medical papers

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Chapitre 1 — Bias vs. Confounding: What's the Difference?

Bias is a flaw in the study itself; confounding is a hidden variable that distorts the true relationship.

Chapitre 2 — Types of Bias You Should Know

Selection bias affects who is in the study; information bias affects how data is measured; publication bias affects what we see in journals.

Chapitre 3 — Confounding: When a Hidden Factor Interferes

A confounder is linked to exposure and outcome but does not lie on the causal pathway; it creates a spurious association.

Chapitre 4 — How to Spot Bias and Confounding in a Paper

Always ask: Could a systematic error or a hidden variable explain these results, or is the association likely real?

Teste-toi

1. What is the main difference between bias and confounding?

AA. Bias is random, confounding is systematic
BB. Bias is a systematic error, confounding is a third variable distorting the association
CC. Bias only occurs in observational studies, confounding only in trials
DD. Bias affects the outcome, confounding affects the exposure
Voir la réponse

Réponse : B — B. Bias is a systematic error, confounding is a third variable distorting the association

Bias is a flaw in the study design or conduct, while confounding is caused by an external variable linked to both exposure and outcome.

2. Which of the following is an example of selection bias?

AA. Patients with a disease recalling past exposures better than controls
BB. A study recruiting only volunteers from a specialty clinic, who may be healthier
CC. A blood pressure monitor that consistently reads 5 mmHg too high
DD. Not publishing studies with negative results
Voir la réponse

Réponse : B — B. A study recruiting only volunteers from a specialty clinic, who may be healthier

Selection bias occurs when the study sample is not representative of the target population due to how participants were chosen.

3. In a study on coffee consumption and pancreatic cancer, smoking is a potential confounder because it is:

AA. Caused by coffee consumption
BB. Associated with both coffee drinking and pancreatic cancer
CC. A result of pancreatic cancer
DD. A random error in the study
Voir la réponse

Réponse : B — B. Associated with both coffee drinking and pancreatic cancer

A confounder must be associated with both the exposure (coffee) and the outcome (pancreatic cancer) but not be on the causal pathway.

4. Recall bias is classified as which type of bias?

AA. Selection bias
BB. Information bias
CC. Confounding
DD. Publication bias
Voir la réponse

Réponse : B — B. Information bias

Recall bias is an information bias because it involves differential accuracy of reported past exposures between cases and controls.

5. Which study design is most effective at controlling for confounding?

AA. Case-control study
BB. Cross-sectional study
CC. Randomized controlled trial
DD. Cohort study
Voir la réponse

Réponse : C — C. Randomized controlled trial

Randomization evenly distributes both known and unknown confounders between groups, minimizing confounding.

6. Publication bias leads to:

AA. An overestimation of treatment effects in the literature
BB. More accurate estimates of effect
CC. Reduced variability between studies
DD. Elimination of confounding
Voir la réponse

Réponse : A — A. An overestimation of treatment effects in the literature

Because positive studies are more likely to be published, the overall literature may suggest larger effects than truly exist.

7. When reading a paper, which question helps you detect potential confounding?

AA. Was the sample size calculated correctly?
BB. Did the authors adjust for variables like age and sex?
CC. Was the p-value less than 0.05?
DD. Was the study double-blinded?
Voir la réponse

Réponse : B — B. Did the authors adjust for variables like age and sex?

Adjusting for potential confounders in the analysis is a key method to reduce confounding, so checking if this was done is crucial.

8. A study finds that people who take vitamin D supplements have a lower risk of multiple sclerosis. However, those who take supplements also tend to have higher income and better healthcare access. This is an example of:

AA. Selection bias
BB. Recall bias
CC. Confounding by socioeconomic status
DD. Publication bias
Voir la réponse

Réponse : C — C. Confounding by socioeconomic status

Socioeconomic status is associated with both supplement use and MS risk, so it could confound the observed association.

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