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ISDS 2012 Conference Abstracts

The Use of the International Classification of Diseases,
Ninth Revision (ICD-9) Coding in Identifying Chronic
Hepatitis B Virus Infection in Health System Data:
Implications for Surveillance
Reena Mahajan*1, Anne C. Moorman1, Stephen J. Liu1, Loralee Rupp2, Monina Klevens1
and (CHeCS) for the Chronic Hepatitis Cohort Investigators3, 2, 1

1Centers for Disease Control and Prevention, Atlanta, GA, USA; 2Henry Ford Health System, Detroit, MI, USA; 3Kaiser Permanente-
Hawaii; Geisinger Health System, Pennsylvania; Kaiser Permanente-Northwest, Oregon, Atlanta, GA, USA

Objective
To evaluate the sensitivity, specificity, positive and negative pre-

dictive values of the ICD-9 coding system for surveillance of chronic
hepatitis B virus infection (HBV) using data from an observational
cohort study in which ICD-9-coded HBV cases were validated by
chart review.

Introduction
In the United States, 800,000- 1.4 million people are chronically

infected with hepatitis B virus (HBV); these persons are at increased
risk for chronic liver disease and its sequelae (CDC, 2010; Wasley,
2010). Current national viral hepatitis surveillance is a passive labo-
ratory-initiated reporting system to state or local health departments
with only 39 health departments reporting chronic HBV infection in
the National Notifiable Disease Surveillance System (NNDSS). Since
active HBV surveillance can be expensive and labor-intensive, the
ICD-9 coding system has been proposed for surveillance of chronic
hepatitis B.

Methods
We examined the electronic health records (EHRs) available as

part of an existing cohort study of persons with chronic viral hepati-
tis. Records from 1.6 million adult patients who had one or more serv-
ices from 2006-2008 in four integrated health care systems were
reviewed. Complex algorithms using laboratory data and/or use of
qualifying hepatitis B ICD-9 codes were applied to EHR patient data
to create the chronic HBV cohort. Disease status was manually vali-
dated by abstractor review of the medical record. Sensitivity, speci-
ficity, positive and negative predictive values were calculated based
upon presence of either one hepatitis B-specific ICD-9 code or two
such ICD-9 codes separated by at least six months.

Results
Of 1,652,055 adult patients, 2,202 (0.1%) met criteria for inclu-

sion into the chronic HBV cohort. Of the 2,202 confirmed cases, the
sensitivity of use of one ICD-9 code was 83.9%, positive predictive
value was 61.0%, specificity was 99.9% and the negative predictive
value was over 99.9% (Table 1). In comparison, use of two hepatitis
B-specific ICD 9 codes separated by six months, resulted in a sensi-
tivity of 58.4%, a positive predictive value of 89.9%, and specificity
and negative predictive value similar to use of one ICD 9 code.

Conclusions
Our findings suggest that use of one or two hepatitis B specific

ICD 9 codes can identify cases with chronic HBV infection. For
health departments with access to electronic medical records, collec-
tion of ICD-9 data may be useful for surveillance and potentially im-
prove reporting of chronic HBV infection.

Measurement of sensitivity, specificity, and predictive values of using one
hepatitis B-specific ICD-9 code among persons receiving services from four
health care systems from 2006-2008

Sensitivity= 1,847/2,202= 83.9%
Specificity= 1,648,671/1,649,853= 99.9%
Positive predictive value= 1,847/3,029= 61.0%
Negative predictive value= 1,648,671/1,649,026= >99.9%

Keywords
surveillance; hepatitis B virus; ICD-9

Acknowledgments

The authors thank Dr. Fujie Xu, Division of Viral Hepatitis, Centers for
Disease Control and Prevention for her helpful suggestions with this
study.

References

1. CDC, 2010. Viral hepatitis statistics and surveillance.
http://www.cdc.gov/hepatitis/Statistics/index.htm. Accessed July 20,
2012

2. Wasley A, Kruszon-Moran D, Kuhnert W, Simard EP, Finelli L, Mc-
Quillan G, et al. The prevalence of hepatitis B virus infection in the
United States in the era of vaccination. J Infect Dis 2010;202:192-
201.

*Reena Mahajan
E-mail: rmahajan1120@yahoo.com

Online Journal of Public Health Informatics * ISSN 1947-2579 * http://ojphi.org * 5(1):e26, 2013