Thanks for the replies.
I would like to summarize my opinion:
- As others pointed out, there are many databases (of good quality) out there which do not have the days_supplied information. There are various methods to substitute this missing information either by parsing a dosage description field or by calculating medians of days_supplied or distances. However, the most powerful methods need the quantity supplied.
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We cannot consider this field as a required field.
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If this information is missing, the ETL process should indicate this by providing a 0 in order to leverage the above mentioned methods.
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If the ETL provides an own guess, there must be reasons that this estimate is better than results from typical analytical methods.
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What we regularly know are the original/intended days supplied (either prescribed or dispensed). Only in rare cases we have data sources which provide stop records. A stop record truncates the original/intended exposure period, i.e. the corrected exposure period may be smaller than the original one (in accordance to the doctorâs intention). I am not aware of an important practical use case where the actual exposure period is longer than the original one (we are not addressing compliance/adherence here just a change of the doctorâs intention).
In particular, the use case described here by @rkboyce is an important but dangerous one: An initial prescription is recorded together with days_supply for this prescription but many undocumented refills occur and are documented only by exposure_end_date.
If the drug_exposure table is abused to document some kind of drug_era periods, analytics will wrongly calculated doses.
We may have to address this problem in the future with additional fields. A rather complex alternative would be to distinguish two cases:
If the corrected information is smaller than the original one it represents a medication stop/change.
If the corrected information is bigger than the original one it represents refills. -
It would be beneficial to have two fields âoriginal intentionâ vs. âcorrected intentionâ because it would give us information about medication stops or changes.
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However, we must know whether both fields refer to this prescription record or to a sequence of hidden ones.
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If we have both fields, we must be clear how to interpret them. My recommendation is to have the âoriginalâ information in the first place and the âcorrectedâ as an additional option only if it differs from the original one.
The proposal may suggests the other way around: The default might be the corrected information, which probably means it holds the intended information if there is no difference. In this case it is important to note that the intended information must be provided if there is a difference. If the intended information is missing in that case the analytics will calculate wrong daily dosage information because it would be based on the wrong (changed) period.- For me it is not important which field is the default as long as a difference is recorded as described above.