For example, a CI study conducted in both poverty-stricken rural Mississippi and the metropolitan Washington, DC, area illustrated that respondents in rural areas with little access to health care were more likely to misunderstand survey questions about various health conditions (i.e., congestive heart failure and COPD) and cancer screening (i.e., mammograms and prostate-specific antigen [PSA] tests). Here, KLK3 is linked to chronic obstructive pulmonary disease.