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Using the Prevalence of an Elevated Serum Alanine Aminotransferase Level for Identifying Communities With a High Prevalence of Hepatitis C Virus Infection
Chong-Shan Wang, MD, MPH;
Shan-Tair Wang, PhD;
Pesus Chou, DrPH
Arch Intern Med. 2001;161:392-394.
ABSTRACT
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Background Antibody to hepatitis C virus (anti-HCV) is a widely accepted method
for the diagnosis of HCV infection. However, it is too expensive to use in
large-scale health surveys.
Objective To investigate the use of the serum alanine aminotransferase (ALT) level
to predict the prevalence of HCV infection.
Patients and Methods A sample of 6095 residents aged 35 years old or older in a small township
of southern Taiwan, Republic of China, were examined in a community health
survey. These persons were walk-ins to the government-sponsored stations after
an intensive health promotion for this survey. Blood samples were obtained
and analyzed for serum ALT levels. The presence of hepatitis B surface antigen
and anti-HCV were determined by enzyme immunoassay methods.
Results The overall prevalences of hepatitis B surface antigens(+), anti-HCV(+),
and elevated ALT levels were 11.8%, 15.0%, and 7.5%, respectively. Among the
13 villages in this community, the prevalence of hepatitis B surface antigen(+)
ranged from 6.8% to 17.3%, anti-HCV(+) ranged from 7.2% to 37.6%, and an elevated
ALT level ranged from 5.8% to 16.5%. A strong positive correlation was found
between the prevalence of an elevated ALT level and anti-HCV(+) (r=
0.91, Spearman rank correlation; P<.001). However, nearly
0 correlation (r= -0.05, P= .87) was obtained
between the prevalence of an elevated serum ALT level and hepatitis B surface
antigen(+).
Conclusion The prevalence of an elevated serum ALT level in a community is a strong
indicator of its prevalence of anti-HCV(+), even in areas where there is a
similar prevalence of hepatitis B virus infection. This result is useful for
economically identifying hyperendemic communities with HCV infection.
INTRODUCTION
HEPATITIS C VIRUS (HCV) infection is an important public health problem.1, 2 This communicable disease is difficult
to treat and frequently causes advanced liver diseases and related extrahepatic
disorders1, 2, 3 and,
thus, its effect on a community with high prevalence is potentially devastating.
An effective way of minimizing the effect is to prevent the disease's further
spread. Identifying the communities at high risk of HCV infection and the
associated risk factors is an important first step.
Antibody to HCV (anti-HCV) test is the accepted method for the diagnosis
of HCV infection. It is routinely used in the screening for HCV infection
among blood donors. However, the anti-HCV test has not been widely used in
routine health examination and community screening for 2 reasons: its high
cost and the difficulty with performing the test in many communities where
there is a lack of both necessary technicians and instruments. Cost and feasibility
are primary considerations in such health surveillance and surveys. To identify
the communities at high risk of HCV infection, there is a need for a much
simpler, cost-effective tool.
The serum alanine aminotransferase (ALT) level test had been shown to
be a viable and cost-effective screening test for HCV infection that could
reduce the incidence of posttransfusion infection.4, 5
However, with the invention of anti-HCV test, the serum ALT level test has
been gradually phased out in blood donor screening because of its lower sensitivity,
which can subject blood recipients to the unnecessary risk of HCV infection.6 Its effectiveness in large-scale screening of HCV
infection also has been questioned because of its unsatisfactory sensitivity.7, 8 Although the serum level test may not
be ideal for the individual diagnosis of HCV infection, we will show that
using the prevalence of an elevated serum ALT level ( 40 U/L) for identifying
communities with high prevalence of HCV infection is valuable.
PARTICIPANTS, MATERIALS, AND METHODS
A sample of 6095 residents aged 35 years or older in a small township
in southern Taiwan, Republic of China, were examined during a community health
survey. These persons were walk-ins to the government-sponsored stations after
an intensive health promotion for this survey. This community has 13 villages
with a population of almost 31 000 people and has been known for its
high prevalence of hepatitis B virus (HBV) and HCV infections.9, 10
Of those living in this township, 8800 were 35 years old or older. Blood samples
were obtained from the participants who were analyzed for serum ALT levels.
The analysis was performed on a kinetic UV test for clinical chemistry analyzers
(Olympus System Reagent, Mills, Ireland). The cutoff value of 40 U/L or higher
was set for the diagnosis of an elevated serum ALT level. Hepatitis B virus
infection was assessed for hepatitis B surface antigen (HBsAg) by optical
density/cutoff ratios and enzyme immunoassay using Murex HBsAg Version I (London,
England), and HCV infection was assessed by the third-generation Murex anti-HCV
enzyme immunoassay, which contains the antigen from the HCV core, nonstructural
3 through 5 regions. For simplicity HBsAg(+) denotes HBsAg(+)/anti-HCV(-),
and anti-HCV(+) denotes HBsAg(-)/anti-HCV(+). Seronegative cases were
HBsAg(-)/anti-HCV(-). The correlation between the prevalence of
an elevated serum ALT level and HBsAg(+) or anti-HCV(+) among the 13 villages
was determined using the Spearman rank correlation.
RESULTS
The prevalence of HBsAg(+) was 11.8% (n = 719), anti-HCV(+) was 15.0%
(n = 917), and elevated serum ALT level was 7.5% (n = 459) for the township.
The village-specific prevalence of HBsAg(+) ranged from 6.8% to 17.3%, anti-HCV(+)
ranged from 7.2% to 37.6%, and elevated serum ALT level ranged from 5.8% to
16.5%. Figure 1 shows the relation
between the prevalence of an elevated serum ALT level and anti-HCV(+) among
the 13 villages, and the relation between the prevalence of an elevated serum
ALT level and HBsAg(+). Spearman rank correlation was calculated as 0.91 (P<.001), and -0.05 (P
= .87), respectively.
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A, The scatterplot of the prevalence of anti-hepatitis C virus
(HCV)(+)
vs elevated serum alanine aminotransferase (ALT) levels (40 U/L) (Spearman
rank correlation coefficient, r = 0.91; P<.001).
B, The scatterplot of the prevalence of hepatitis B surface antigens (HBsAg)(+)
vs elevated serum ALT levels (Spearman rank
correlation coefficient, r = -0.05;
P = .87).
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COMMENT
We found a strongly positive correlation between the prevalence of an
elevated serum ALT level and anti-HCV(+) based on a sample of adults aged
35 years or older. This finding suggests that we can use the prevalence of
an elevated serum ALT level for identifying the communities with high prevalence
of HCV infection in this adult group. Considering that the per unit cost of
the anti-HCV test is 5 to 25 times that of the serum ALT level test, the overall
cost for conducting such a regional or national survey of HVC infection can
be significantly reduced using the serum ALT level test. Moreover, the serum
ALT level test is a routinely used liver function test in clinical practice
and periodic health examination. Therefore, performing the serum ALT level
test in the field is much more feasible than performing the anti-HCV test.
Our data have important implications in terms of cost and feasibility for
monitoring a communicable disease in communities, particularly in hyperendemic
areas.
In contrast to HCV infection, we found no correlation between the prevalence
of an elevated serum ALT level and HBsAg(+). Taiwan is a part of the world
with high rates of HBV infection, so if HBV does not interfere with the use
of the serum ALT level for the detection of HCV infection in Taiwan, it should
not be a problem anywhere. In summary, the prevalence of an elevated serum
ALT level is a valuable index for identifying the communities at the high
risk of HCV infection. The increased population with an elevated serum ALT
level is more likely to be attributed to HCV infection.
AUTHOR INFORMATION
Accepted for publication July 28, 2000.
This investigation was supported in part by funds from the A-Lein Community
Health Promotion Committee, and C. T. Hsu Cancer Research Foundation, Taipei,
Taiwan.
We are indebted to Walter J. Rogan, MD, National Institute of Environmental
Health Sciences, Triangle Park, NC, for his excellent comments on the manuscript
during its preparation; to the staff and volunteers of the A-Lein Community
Health Center, Kaoshsiung (Taiwan) County, for their assistance in data collection;
and to the T'ai-nan Blood Center of Chinese Blood Service Foundation, T'ai-nan,
Taiwan, for assistance with laboratory analysis.
From the A-Lein Community Health Center, Kaohsiung (Taiwan) County
(Dr C.-S. Wang); Department of Public Health, College of Medicine, National
Cheng Kung University, T'ai-nan, Taiwan (Drs C.-S. Wang and S.-T. Wang); and
the Community Medicine Research Center and Institute of Public Health, National
Yang-Ming University, Taipei, Taiwan (Dr Chou).
Corresponding author and reprints: Pesus Chou, DrPH, National Yang-Ming
University, Institute of Public Health, Shih-Pai, Taipei 112, Taiwan, Republic
of China (e-mail: pschou{at}ym.edu.tw).
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