Question

what are the necessary steps researchers are taking to avoid the bias and ensure that they have a significant and accurate estimate of the true association between the exposure and the outcome?

Answer 1

Type of Bias	How to Avoid
Pre-trial bias
Flawed study design	Clearly define risk and outcome, preferably with objective or validated methods. Standardize and blind data collection.
Selection bias	Select patients using rigorous criteria to avoid confounding results. Patients should originate from the same general population. Well designed, prospective studies help to avoid selection bias as the outcome is unknown at the time of enrollment.
Channeling bias	Assign patients to study cohorts using rigorous criteria.

Type of Bias	How to Avoid
Bias during trial
Interviewer bias	Standardize interviewer's interaction with the patient. Blind interviewer to exposure status.
Chronology bias	Prospective studies can eliminate chronology bias. Avoid using historic controls (confounding by secular trends).
Recall bias	Use objective data sources whenever possible. When using subjective data sources, corroborate with the medical record. Conduct prospective studies because the outcome is unknown at the time of patient enrollment.
Transfer bias	Carefully design plan for lost-to-followup patients prior to the study.
Exposure Misclassification	Clearly define exposure prior to the study. Avoid using proxies of exposure.
Outcome Misclassification	Use objective diagnostic studies or validated measures as a primary outcome.
Performance bias	Consider cluster stratification to minimize variability in surgical technique.

Type of Bias	How to Avoid
Bias after trial
Citation bias	Register trial with an accepted clinical trials registry. Check registries for similar unpublished or in-progress trials prior to publication.
Confounding	Known confounders can be controlled with study design (case-control design or randomization) or during data analysis (regression). Unknown confounders can only be controlled with randomization.