MIMIC-III: Negative cultures and microbiologyevents

Question

In MIMIC-III, where do negative cultures appear? Is this different between CareVue patients and Metavision patients?

Despite the documentation's assertion (here) that "If the specimen is null, then the culture had no growth reported.", there are very few cases where either the spec_itemid or org_itemid are empty in the microbiologyevents table(I think it's less than 2k out of 328k). Also, in a manual inspection, it looks like most rows have an antibiotic test done, so as to determine sensitivity of the culture.

PROCEDUREEVENTS_MV seems to have information on cultures for Metavision patients, but this whole table confuses me too.

Edit: Clarified that paragraph 2 refers to the microbiologyevents table.

Answer 1

Negative cultures were added to the microbiologyevents table in version 1.4 of MIMIC-III: http://mimic.physionet.org/about/releasenotes/

• #188 - Negative microbiology cultures are now recorded in MICROBIOLOGYEVENTS - negative cultures can be identified by a NULL value for the organism name (ORG_NAME).

Negative cultures were not available in prior versions of MIMIC-III.

Answer 2

From what it appears, an entry in the microbiologyevents table means that the test was performed, and a NULL value indicates that no microbiological agent was detected, for that particular agent in that particular specimen at that particular date/time stamp.