Finding lab data for MIMIC-IV-ED patients?

[tchang1997]

I am trying to work with lab data for patients in MIMIC-IV-ED. So far, I've been using the labevents table in MIMIC-IV. However, I've run into difficulties finding data for patients with a null hadm_id. I've tried to link such patients with the labevents table without much success — I describe my strategy in more depth here.

(1) For patients with a non-null hadm_id, obtaining their labevents info is straightforward since labevents stores the hadm_id.
(2) I mostly have problems with patients with a null hadm_id. I tried to link labevents to ED stays as follows:

• For each labevent, retrieve all ED stays with a matching subject_id
• Find the ED stay such that the current lab's charttime falls between the intime and outtime attributes

In other words, I'm trying to find all lab tests done for a particular patient at any time, and filling in the stay_id for each lab event based on whether the charttime falls within any of that patient's ED stays.

Based on this strategy, however, <1% of all patients with a null hadm_id are tested, which seems unreasonably low, even though we're looking at non-admitted patients. I get higher testing rates when linking to a test in microbiologyevents instead of labevents, but they still seem low. Is lab data for non-admitted patients in MIMIC-IV-ED available anywhere else in MIMIC? Or is there a more reliable strategy for linking labevents to ED stays?

[alistairewj]

I agree <1% feels too low. Probably just a slight mismatch in timing. I would add a fuzzy window of +- 8 hours to the intime/outtime for ED stays and see if you still have a very low number of labs. I would be interested to see the percentages if you post them here.