In epidemiology, what does "surveillance bias" refer to?

Surveillance bias refers to the systematic distortion that occurs when the methods used to collect data are influenced by the presence or outcomes of the conditions being studied. In epidemiology, this type of bias can arise when the monitoring or observation of individuals is more rigorous for certain groups or conditions. For example, if a particular disease is known to have serious consequences, individuals with symptoms may be more closely monitored or have more tests performed, leading to a higher reported incidence of the disease among those individuals compared to others who may not be as closely observed.

This bias is significant because it can skew research findings by creating an overrepresentation of certain outcomes in the data, potentially leading researchers to draw inaccurate conclusions about prevalence or risk factors associated with those outcomes. Understanding surveillance bias is essential for interpreting epidemiological studies accurately, as it highlights the importance of consistent and unbiased data collection methods to ensure valid results.