Calculation function within Cohort Definitions

Business Requirements

As the OMOP CDM Data Set entries don't necessary contain the events of interest for there further inclusion in analyses there should be a possibility:

• to identify the start of a pregnancy based on the birth event code
• to perform calculations between multiple Measurements and the result can be used further in Cohort Definitions

Design Ideas and Functional Requirements

Calculations between multiple Measurements use case

There are two alternative Circe model extensions to consider:

• a new Combined Measurement with a possibility to define the first and the second Measurements used in a calculation as its attributes

• an extension of the existing Measurement with a new attribute which will define an "adjacent" Measurement to be included in calculations (suggested by @chrisknoll in opposite to the initial idea above)

To avoid any ambiguity when an event in the calculation is taken into consideration in a formula there should be a possibility to define if the first or the last one should be used when multiple. Belonging to the same Visit option shouldn't be neglected as well when required

The calculations should be allowed between "value as number" attributes in Measurements and the following operators should be supported "+", "-", "*", "/"

The start of a pregnancy use case

The date adjustment attribute is suggested to use with an additional sign control ("-" or "+")

Note: As the edit controls support entering negative numbers introducing the new sign controls are rather redundant

Open Questions

• it is possible that Measurements in a formula might have different units so that there should be a way to define a common denominator so that the result of the formula is adequate

@mrechkem @Sathyaraos
@tomwhite (please supplement the issue with any further use cases)