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. Author manuscript; available in PMC: 2019 Jul 14.
Published in final edited form as: Int J Med Inform. 2014 Oct 12;84(1):76–84. doi: 10.1016/j.ijmedinf.2014.10.004

Table 2.

A summary of the mappings of data variables, joins, and aggregate functions to HITSP data elements within queries. Unless specified otherwise, the results are for statistics across studies.

Statistic Selection Criteria Data Variables
Average number of data elements per study 4.46 6.44
Range of number of data elements 1–12 1–15
Median number of data elements 4 6
Number of distinct data elements 39 50
Unmapped data elements 25 60
Number (percent) of studies with at least one unmapped variable 19 (18.3%) 35 (33.7%)
Number of joins across studies 36 86
Number (percent) of studies requiring joins 25 (24.0%) 49 (47.1%)
Joins per study range 1–3 range 1–9
Modules in joins 6 8
Data elements in joins 20 19
Number of aggregates 5 in 5 studies 27 in 22 studies
Aggregate functions used Count and Last Count, last, minimum, maximum, average, first
Number (percent) of studies including both join and aggregate 2 (1.9%) 8 (7.7%)