Recommended update: Incorporate time unit definitions and time interval calculation conventions into the QDM specifications to eliminate independent implementation of measure logic for dealing with time.
The eCQM logic guidance document provides time unit definitions and time interval calculation conventions. These definitions and conventions were established leading up to the release of the 2014 Stage 2 clinical quality measures to eliminate the ambiguity that existed in the calculation of date and time differences. There are several potential interpretations of how to calculate a difference in times based on a unit, and the definition of a given unit of time. For instance, does the term “day” represent a business day excluding weekends and holidays, does it represent an 8 hour day of work, or does it represent a calendar day. Similarly, when comparing differences in time using units, it is not always clear how those units are evaluated, and if all components of the date and time are considered as part of the calculation. For instance, does a duration calculated in years take into account days, hours, minutes, or seconds? These ambiguities in the calculation of dates and times can lead to independent implementations of the measure logic that calculate differently based on which assumptions were coded into the implementation. Incorporating the time unit definitions and time interval calculation conventions into the QDM specification eliminates these ambiguities and provides examples to illustrate the appropriate calculation. This provides both measure authors and measure implementers with a single gold-source reference for timing related information.