EXHIBIT 2.

Use of negative patient descriptors in electronic health records (EHRs) of a large urban academic medical center in Chicago, Illinois, by encounter characteristics, January 2019-October 2020

			Negative patient descriptors in EHR
	Encounters (N = 33,142)		None (n = 30,289)		One or more (n = 2,853)
Encounter characteristics	% or mean	No. or SD	% or mean	No. or SD	% or mean	No. or SD
Charlson Comorbidity Index (mean and SD)	1.4	0.01	1.6	0.01	2.4	0.03
Encounter length, days (mean and SD)	4.4	0.04	5.8	0.06	7.5	0.1
Timing of encountera (% and number)
Before March 1, 2020	19.3	6,401	17.1	5,718	26.0	1,740
On or after March 1, 2020	80.7	26,741	82.9	27,690	74.1	4,965
Encounter location (% and number)
Inpatient	46.6	15,459	50.7	16,928	68.0	4,556
Outpatient	51.8	17,157	48.0	16,018	31.0	2,075
Emergency department	1.6	526	1.4	462	1.1	74

source Authors’ analysis of data from the University of Chicago Center for Research Informatics COVID-19 data mart. notes Results reflect detection of a negative patient descriptor (none versus at least one) in the patient’s history and physical notes. SD is standard deviation.

^aWe selected March 1, 2020 as an approximate date at which providers’ behavior may have changed in conjunction with the COVID-19 pandemic. The first cases in Illinois that were not linked to travel from China were reported February 29 and March 2, 2020; see Illinois Department of Public Health [Internet]. Springfield (IL): IDPH. Press release, State of Illinois public health officials announce new presumptive positive COVID-19 case in Illinois; 2020 Feb 29 [cited 2021 Dec 8]. Available from: https://dph.illinois.gov/resource-center/news/2020/march/state-illinois-public-health-officials-announce-new-presumptive-positive-covid-19-caseillinois.html. Local medical institutions began implementing COVID-19 measures, with government measures to follow shortly thereafter.