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ISDS 2012 Conference Abstracts

Can We Use Syndromic Surveillance Data to Identify
Primary Care Visits to NYC EDs?
Jessica Athens*

New York City Department of Health and Mental Hygiene, New York City, NY, USA

Objective
To develop a syndrome classification based on patient chief com-

plaint to (1) estimate the proportion of primary care-related emer-
gency department (ED) visits in New York City (NYC) hospitals and
(2) explore predictors of such visits.

Introduction
NYC EDs saw nearly 4 million visits in 2011. Studies have demon-

strated that non-urgent visits can account for more than 50% of vis-
its to EDs [1,2]. Designed to provide rapid diagnosis and first-line
treatment of serious illness, EDs often function as a primary care site
due to their accessibility. Unfortunately, use of EDs for primary care
may affect their ability to meet the needs of severely ill patients.

Methods
We examined syndromic surveillance data from 45 hospitals in

NYC for 2011 and classified visits into a primary care syndrome
based on the chief complaint field. Data from 4 hospitals were omit-
ted due to data quality issues, as were records from non-NYC resi-
dents. Primary care (PC) syndrome visits included visits recorded as
referrals, screenings, suture removal/dressing changes, or medication
refills; records with a blank or non-informative (e.g. “X”) chief com-
plaint field were omitted from analysis. Using unique patient IDs, we
identified patients who visited the same ED multiple times in the pre-
vious 12 months. A hierarchical generalized linear mixed effects
model with hospital-level random effects was used to explore patient
characteristics associated with PC syndrome visits. The model in-
cluded a random intercept for hospital and the following covariates:
duplicate visit, patient gender and age group (ages 0-4, 5-17, 18-64,
and 65+), and time of visit (midnight to 8 AM, 8 AM to midnight).
Covariates for month and day of week were included to control for
temporal trends in ED visits. Model parameters were estimated by
maximum likelihood. Estimation was performed in SAS version 9.2
[3] using the GLIMMIX procedure.

Results
Citywide, 7.5% (N=190,431) of visits to EDs during 2011 were

classified as PC syndrome visits, but varied by hospital with a median
of 4.6% (IQR: 3% to 9%) across hospitals.The average proportion of
PC syndrome visits varied by hospital. Of the 45 hospitals included
in the analysis, 18 had a lower baseline, 13 were the same, and 14
had a higher baseline than the city mean. Hospitals with a larger cen-
sus had a larger proportion of PC syndrome visits.

Age had a significant effect on the odds of a PC syndrome visit;
ages 0–4 had the greatest odds of a PC syndrome visit relative to the
65+ age group. Visits from patients ages 5–17 and 18–64 were also

more likely to be primary care visits. Patients with repeat visits were
more likely to have PC syndrome visits. Female gender and early
morning visits (12A–8A) were associated with lower odds of a PC
syndrome visit.

Conclusions
With limited detail on patient visits, our syndrome likely under-

counts primary care visits to EDs. However, the relationships between
our explanatory variables—age, time of day, and duplicate visits—
and PC syndrome visits are consistent with the literature on ED usage
for primary care. Gender is an exception [1], but earlier findings may
be confounded by the fact that females seek health care more fre-
quently in general. The variation in PC syndrome visits among NYC
EDs is significant and may be explained by hospital or community
measures not captured in our model, such as clinic wait times, ED
capacity, or insurance coverage. In fact, disparities in such predictors
of PC syndrome visits could be targets for interventions. Our ability
to replicate previous findings on the use of EDs for primary care vis-
its suggests that syndromic data may be a near real-time data source
for following trends in such visits.

Predictors of PC Syndrome Visits

All covariates significant at p < .001.

Keywords
Misuse of emergency medical services; Primary care; Variation in
emergency department use

References

1. Carret M, Gastal Fass A, Rodrigues Domingues A. Inappropriate use of
emergency services: a systematic review of prevalence and associ-
ated factors. Cad. Saúde Pública. 2009;25(1): 7–28.

2. Tang N, Stein J, Hsia RY, Masselli JH, Gonzales R. Trends and char-
acteristics of US emergency department visits, 1997–2007. JAMA.
2010;304(6):664–70. 

3. SAS Institute, Inc., Cary, NC.

*Jessica Athens
E-mail: jathens@health.nyc.gov

Online Journal of Public Health Informatics * ISSN 1947-2579 * http://ojphi.org * 5(1):e56, 2013