Final answer:
The trend that necessitated the development of data sets in addition to the UHDDS in the 1980s was the proliferation of ambulatory services and procedures.
Step-by-step explanation:
In the 1980s, the trend that necessitated the development of data sets in addition to the UHDDS was ambulatory services and procedures proliferated.
The increase in ambulatory services and procedures led to a greater need for tracking and recording data on outpatient care in addition to the traditional data collected for inpatient care.
For example, as more procedures were being performed in outpatient settings, it became important to track the length of stay and outcome for these patients. This required the development of data sets specific to ambulatory care.