In the other type of health care database that we discuss in this chapter, there are multiple columns for each patient observation. It is more difficult to find both the most frequently occurring codes, or to find patients with specific codes for the purpose of extraction. For this reason, many studies focus on the primary diagnosis or procedure. We will provide the programming necessary to find the most frequent codes and to find the patients who have a specific condition. Another aspect of preprocessing we will explore in this chapter using the National Inpatient Sample is that of propensity scoring. When it is not possible to perform a randomized, controlled trial, an attempt is made to emulate such a trial by comparing two observational subgroups. The two groups are matched based upon demographic factors and related patient conditions. It is possible to define a level of patient severity and then to match patients with the severity level as part of the propensity score.
Risk of pacemaker implantation after radiotherapy for breast cancer: A study based on French nationwide health care database sample
