How to populate days_supply when days supply is negative in the source

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How to populate days_supply when days supply is negative in the source

CDM or THEMIS convention?

Themis

Table or Field level?

Field

Is this a general convention?

No

Summary of issues

• There are instances when days_supply for a drug is negative in the source data

Summary of answer

• The CDM documentation states: Negative values are not allowed. If the source has negative days supply the record should be dropped as it is unknown if the patient actually took the drug.
• Several actions are possible: 1) record is not trustworthy and we remove the record entirely. 2) we trust the record and leave days_supply empty or 3) record needs to be combined with other record (e.g. reversal of prescription). High values (>365 days) should be investigated. If considered an error in the source data (e.g. typo), the value needs to be excluded to prevent creation of unrealistic long eras.

Related links

• CDM documentation: https://ohdsi.github.io/CommonDataModel/cdm54.html#drug_exposure
• Forum posts: https://forums.ohdsi.org/t/days-supply-yet-again/4741/16
• Themis repo ratified convention: https://github.com/OHDSI/Themis/issues/76

[clairblacketer]

Issue # and location

• Themis issue #76

Issue summary

How should drug exposure records with negative days supply be handled in the CDM?

Convention type

Table

CDM table

drug_exposure

CDM field

days_supply

Links to issue discussion

• OHDSI Forums discussion
• CDM Documentation

Provenance of data

General

The ratified convention

The CDM documentation states: Negative values are not allowed. If the source has negative days supply the record should be dropped as it is unknown if the patient actually took the drug.

Several actions are possible: 1) record is not trustworthy and we remove the record entirely. 2) we trust the record and leave days_supply empty or 3) record needs to be combined with other record (e.g. reversal of prescription). High values (>365 days) should be investigated. If considered an error in the source data (e.g. typo), the value needs to be excluded to prevent creation of unrealistic long eras.

Date of ratification/published

July 5, 2023

Downstream implications

No

Link to DQD check

Yes - plausibleValueLow (page under construction)

Related conventions/further information

NA

#Tags drug_exposure, days_supply