Rapid diagnostic HCV antibody assays

Article (PDF Available)inAntiviral therapy 17(7 Pt B):1409-13 · January 2012with53 Reads
DOI: 10.3851/IMP2470 · Source: PubMed
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Abstract
Approximately 4.1 million Americans have been infected with HCV and 45-85% of chronically infected persons are unaware of their status. Rapid anti-HCV assays can assist and expedite the identification of those unaware of their infection. Performance characteristics of pre-market rapid anti-HCV assays (Chembio, MedMira and OraSure) have been evaluated. Their sensitivity (78.9-99.3%) and specificity (80-100%) varied. Future investigations could include evaluation of rapid anti-HCV tests in persons who are coinfected with HCV and HIV, and development of rapid HCV-antigen tests and nucleic acid tests.
2012 Published by International Medical Press 1359-6535 (print) 2040-2058 (online) 1409
Antiviral Therapy 2012; 17:1409–1413 (doi: 10.3851/IMP2470)
Approximately 4.1 million Americans have been infected
with HCV and 45–85% of chronically infected persons
are unaware of their status. Rapid anti-HCV assays can
assist and expedite the identication of those unaware of
their infection. Performance characteristics of pre-market
rapid anti-HCV assays (Chembio, MedMira and OraSure)
have been evaluated. Their sensitivity (78.9–99.3%) and
specicity (80–100%) varied. Future investigations could
include evaluation of rapid anti-HCV tests in persons who
are coinfected with HCV and HIV, and development of
rapid HCV-antigen tests and nucleic acid tests.
The Centers for Disease Control and Prevention (CDC)
estimates that 4.1 million Americans have been infected
with HCV, 75–80% of whom are living with chronic
HCV infection [1]. CDC recommends routine HCV
antibody (anti-HCV immunoglobulin G) testing for
persons at risk of infection [2]. Yet studies estimate that
45–85% of HCV-infected persons are unaware of their
status [3–5]. Knowledge of HCV infection status is nec-
essary for persons to make health promoting behaviour
changes and treatment decisions.
Persons who inject drugs (PWID) account for 58%
of all anti-HCV-positive persons in the US [1] and CDC
estimates that injection drug use (IDU) accounted for
56% of acute hepatitis C cases in the US in 2009 [6].
The estimated HCV prevalence among PWID ranges
from 30% to 70%, depending on frequency and dura-
tion of use [7,8], and the incidence ranges from 16%
to 42% per year [9,10]. Younger PWID (<30 years old)
have lower prevalence rates, ranging between 10% and
36%, but this still translates to >1/3 of young PWID
becoming infected [11,12]. At least 50% of persons who
have a documented risk factor for HCV infection [2] do
not receive anti-HCV testing [3,4]. Not only are PWID
at increased risk for hepatitis C, but they are also at risk
for infection by HIV [13]. The prevalence of HIV infec-
tion among PWID is 6.2% [14] and CDC recommends
HCV screening of all HIV-infected individuals [15]. The
prevalence of anti-HCV immunoglobulin G among per-
sons infected with HIV is 24% and increases to 81%
when the risk factor identied is IDU [13].
Although PWIDs are at high risk for blood-borne
infections such as HCV and HIV, they have limited
access to health care [16]. Currently, PWID are tested
infrequently for anti-HCV immunoglobulin G and
many of those who do test positive do not receive
treatment because of comorbidities or contraindica-
tions, ongoing drug use, or reluctance by their physi-
cians to treat. Additionally, many PWID who are tested
for HCV using conventional assays do not return to
receive their results. Point-of-care, rapid HCV test-
ing enables the delivery of results at the time of test-
ing [17]. PWID who receive rapid HIV tests have been
shown to be more likely to be informed of their results
than those tested with conventional assays, who must
return at a later date [18].
Here, we summarize the outcomes of six studies
[17,19–23] conducted in the US that examined the per-
formance characteristics of rapid anti-HCV tests and
propose a research agenda to support their adoption
in the eld.
Evaluation strategy
The six studies use lateral-ow immuno-chromato-
graphic assay devices for testing serum, ngerstick
blood and oral uid, and originate from three manu-
facturers (Chembio [Medford, NY, USA], MedMira
[Halifax, NS, Canada] and OraSure [Bethlehem, PA,
USA]). Rapid test performance was evaluated using
a standard algorithm recommended by CDC [24].
Discordant results were either tested for active HCV
infection or for association with biological factors
such as HIV status, age, sex and race/ethnicity. Active
HCV infection was determined by quantitative nucleic
Review
Rapid diagnostic HCV antibody assays
Bryce D Smith
1
*, Amy Jewett
1
, Jan Drobeniuc
1
, Saleem Kamili
1
1
Division of Viral Hepatitis, Centers for Disease Control and Prevention, Atlanta, GA, USA
*Corresponding author e-mail: bli1@cdc.gov
Introduction
AVT-11-SP-2547_Smith.indd 1409 03/12/2012 12:09:15
2012 Published by International Medical Press1410
BD Smith et al.
acid testing (NAT) which detects the presence of the
HCV RNA.
Rapid assays
Resource constraints, site-specic issues, and specimen
type limited the ability to analyse each specimen fully,
resulting in different sample sizes. The Chembio assay
was evaluated in three studies using serum [22], nger-
stick blood [17,23] and oral uid [17,23] from PWID
(n=2,357). The MedMira assay was evaluated in three
studies using serum [22] and ngerstick blood [23]
from PWID (n=1,940). The OraSure assay was evalu-
ated in ve studies, using serum [20–22], ngerstick
blood [20,21,23] and oral uid [19–21,23] from PWID,
[17,19,22,23] low-risk individuals [21], and those with
signs or symptoms of hepatitis C infection [20] (n=5,058).
Reference assays
All of the studies employed the CDC testing algorithm
as reference for evaluation of test performance. The
CDC algorithm uses previously established signal- to-
cutoff (s/co) ratios unique to each immunoassay to
determine the true anti-HCV status. Positivity is dened
by either reactivity by the conventional enzyme immu-
noassay (EIA) being above an established s/co thresh-
old or reactivity in recombinant immunoblot (RIBA)
conrmatory test. Negativity is dened by either non-
reactivity or negativity by RIBA. Three of the studies
also included comparison to algorithms specic to the
respective manufacturer’s inserts [17,22,23]. Addi-
tionally, one of the sites in the eld study [23] did not
utilize the CDC algorithm and therefore the reported
results were based upon comparison with the conven-
tional EIA only.
Sensitivity and specicity
Across all studies, sensitivity was dened as the number
of positive specimens detected by the rapid assay divided
by the total number of positive specimens as per the
CDC testing algorithm. Specicity was dened as the
number of negative specimens identied by the rapid
assay divided by the total number of negative specimens
as per the CDC algorithm.
Results
Overall, sensitivity and specicity was highest when
using serum specimens as compared to ngerstick
blood and oral uid specimens. The sensitivity of the
OraSure assay was higher than that of Chembio or
MedMira (Table 1).
False-negative and false-positive results occurred with
all assays and specimen types. The MedMira assay yielded
the largest proportion of false-negative results (ranging
from 8% to 19%) as compared to the Chembio (0.4–
7%) and OraSure (0–6%) assays. In two studies, false-
negative results were associated with HIV-positivity. In
the laboratory setting the Chembio assay (adjusted [a]OR
11.0; 95% CI 2.5, 48.2) and the MedMira assay (aOR
4.0; 95% CI 1.5, 10.2) were more likely to provide false-
negative results if the specimens were also HIV- positive.
In one eld setting, the Chembio oral assay (aOR 9.1;
95% CI 2.1, 39.3) was more likely to produce false-
negative results if the specimens were also HIV-positive.
Study Assay Specimen type n Sensitivity, % Specicity, %
Drobnik et al. [19], 2011
a
OraSure Oral uid 503 93.9 99.5
Jewett et al. [17], 2012 Chembio Oral uid 407 85.4 100
Fingerstick 407 97.1 99.0
MedMira Fingerstick 407 80.0 100
Lee et al. [20], 2011
a
OraSure Serum 2,180 99.9 99.9
Fingerstick 2,176 99.7 99.9
Oral uid 2,176 98.1 99.6
Lee et al. [21], 2010
a
OraSure Serum 572 100 99.8
Fingerstick 572 100 100
Oral uid 572 99.2 100
Smith et al. [22], 2011 Chembio Serum 1,081 97.8 99.8
MedMira Serum 1,081 88.3 99.8
OraSure Serum 1,081 99.3 99.5
Smith et al. [23], 2011 Chembio Oral uid
b
476 91.2–92.2 81.6–97.7
Fingerstick 385 94.0 97.1
MedMira
c
Fingerstick 432 78.9 83.3
OraSure Oral uid
b
549 92.2–94.7 92.1–97.2
Fingerstick 265 97.4 98.6
Table 1. Performance characteristics of pre-market rapid anti-HCV assays
a
Financial relationship with OraSure.
b
Testing at two different sites resulted in multiple sensitivities and specicities.
c
Compared to conventional enzyme immunoassay only.
AVT-11-SP-2547_Smith.indd 1410 03/12/2012 12:09:16
Rapid diagnostic HCV antibody assays
Antiviral Therapy 17.7 Pt B 1411
Discussion
The sensitivity and specicity of rapid anti-HCV assays
varied across the six studies. Using serum specimens
resulted in increased sensitivity as compared with n-
gerstick blood or oral uid specimens. The OraSure
assay had a higher sensitivity than the other 2 assays.
In one study, the OraSure assay outperformed the con-
ventional EIA [19]. Of 10 specimens with discordant
results, 5 of 6 specimens that were OraSure-negative
and EIA-positive had no detectable HCV RNA, and 2
specimens that were OraSure-positive and EIA-negative
were HCV-RNA-positive. Results from the OraSure
test seemed more concordant with NAT than from EIA.
Whereas rapid assays provide information about anti-
HCV immunoglobulin G which is a marker of active
as well as resolved infection, NATs provide direct evi-
dence of active HCV infection. This is an important
distinction because between 15% and 33% of patients
spontaneously clear the virus [25] resulting in an anti-
body-positive/NAT-negative result. Furthermore, HCV-
infected patients who achieve sustained virological
response after antiviral therapy will also demonstrate
the same antibody-positive/NAT-negative prole.
False anti-HCV results occurred for all assays in all
settings, but false results were not signicantly associated
with the selected demographic variables studied (HIV
status, age, race/ethnicity or sex). For example, in one
study, false-negative results were more likely to occur
among females when using the MedMira assay [17]. In
contrast, female sex was not associated with false results
for any other assay or evaluation.
False anti-HCV-negative results from the Chembio
and MedMira assays occurred more often when the
specimen was from persons coinfected with HIV, simi-
lar to the ndings of other studies using other assays
[26–28]. Of the 43 HIV-positive specimens in one study,
60% were anti-HCV-positive; HIV-positive specimens
were between four and eleven times more likely to pro-
duce a false-negative rapid assay result [22]. This issue
is of particular concern because the prevalence of HCV
infection among HIV-positive persons is high (24%)
and, conversely, 81% of HIV-positive persons with a
history of IDU are anti-HCV-positive [13]. HIV–HCV-
coinfected persons are at a greater risk of progressing
to an AIDS-dening event or death than those who are
HIV monoinfected [29], and progress to end-stage liver
disease in less than half the time of HCV-monoinfected
persons [30,31].
In one study [23], eld staff reported on implica-
tions of implementing rapid HCV testing in their set-
tings. They reported that rapid testing for anti-HCV
overcomes barriers to receiving referrals for NAT,
medical care and other services. Prior to the study,
eld staff expressed concern that the time required
for HCV testing would impede the HIV testing pro-
cess. While they reported that rapid anti-HCV testing
was time consuming, they also reported that it did not
have a negative impact on HIV testing. However, staff
reported a need for standardized educational materi-
als and counselling messages. Demonstration studies
are being conducted to evaluate the implementation of
rapid anti-HCV assays, new educational materials, and
counselling messages into HIV testing settings to better
understand the impact of introducing a new test in an
existing setting and how this may inuence site opera-
tions. Further evaluation is required to understand the
impact of rapid anti-HCV testing in other settings, such
as emergency departments and primary care clinics
with limited access to laboratories.
The OraSure rapid anti-HCV test, recently approved
by FDA, enables testing in settings where HCV testing
has previously been limited. Rapid assays are useful for
increasing testing opportunities and address the public
health problem of under-diagnosis of HCV infection.
Other benets include patients being able to receive test
results and prevention counselling messages during the
same visit, and that they can receive expedited referral
for follow-up testing and care.
In contrast to conventional assays, rapid assays ena-
ble specimens (for example, ngerstick blood or oral
uid) to be collected and tested at the point-of-care and
do not require a follow-up visit to receive test results.
Of persons who consented to an HIV rapid test, 99%
received their results and prevention counselling and
>94% went to their rst clinic appointment [26,32,33].
Since rapid HIV testing improves receipt of HIV test
results [26–28,34], access to care and health outcomes
[26,32,33], it follows that rapid anti-HCV assays can
similarly benet high-risk populations. Rapid, point-
of-care testing for HCV can expedite and assist in the
identication of those HCV-infected persons who are
unaware of their infection, presenting new opportuni-
ties to provide prevention counselling messages and
referrals for follow-up.
Anti-HCV tests detect both current and past HCV
infections, but cannot distinguish between them. Per-
sons who have positive anti-HCV test results must also
be tested with another assay – currently a NAT – to
determine the state of infection. NAT is more expensive
and labour-intensive than anti-HCV testing. However,
the recently-developed HCV core antigen (HCV Ag) test
has the potential to be used as a relatively less expensive
reex test for individuals who are anti-HCV-positive
and aid in distinguishing resolved from active infec-
tions. A quantitative antigen assay, the Architect HCV
Ag assay (Abbott, Abbott Park, IL, USA), performed
on an automated platform, is now commercially avail-
able in Europe [35]. Several studies in blood donors
have shown the detection of HCV core Ag within the
AVT-11-SP-2547_Smith.indd 1411 03/12/2012 12:09:16
BD Smith et al.
2012 Published by International Medical Press1412
rst 2 weeks of acute infection [36]. The advantages of
HCV Ag assay are that it is an immunoassay, does not
require the same labour-intensive and expensive sam-
ple processing, as in molecular assays, and its detection
conrms active infection; however, the test has a lower
sensitivity when compared to NAT.
The evaluation studies described in this paper have
some limitations. The total number of samples tested
by the OraSure assay was greater than the number of
samples tested by the Chembio and MedMira assays,
providing OraSure with more opportunities for evalu-
ation. Investigators of three of the six studies reviewed
[19–21] had nancial relationships with OraSure. The
evaluation of the MedMira assay also was limited in
that the platform did not allow for oral uid testing. In
one eld setting, the MedMira assay was evaluated with-
out incorporating the CDC algorithm in the analysis of
results [22]. The MedMira rapid assay results were com-
pared to results from the screening EIA only and may
have resulted in a lower sensitivity than if compared to
the CDC algorithm. Lastly, none of the studies included
in the review had more than 50 HIV–HCV-coinfected
specimens to rene the level of precision required for an
acceptable evaluation of such specimens.
Conclusions
Anti-HCV rapid tests can play a signicant role in
increasing the proportion of HCV-infected persons
who are aware of their infection status, especially
among at-risk populations. Further studies are needed
to evaluate the performance characteristics of the
rapid anti-HCV assay for specimens from HIV–HCV-
coinfected persons. Finally, future research should be
targeted towards the development of immunoassays
for detection of HCV antigen and NAT in rapid test
formats.
Disclosure statement
The authors declare no competing interests. The ndings
and conclusions in this report are those of the authors
and do not necessarily represent the ofcial position of
the Centers for Disease Control and Prevention.
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Accepted 8 June 2012; published online 7 December 2012
AVT-11-SP-2547_Smith.indd 1413 03/12/2012 12:09:16
    • "Among immuno-competent population reliability of ICT is 95%; while in immunocompromised , it drops to 77.5 % [14] [16] Performance characteristics of pre-market rapid anti-HCV varied in their sensitivity is (78.9-99.3%) and specificity (80- 100%) [14] [15] [16]. "
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    • "However, now that rapid tests are accessible for more widespread anti-HCV screening, the practice of confirming reactivities generated from screening tests would require reconsideration. Smith et al. [7] in their review of rapid assays in this issue note that, as a whole, the assays yielded satisfactory performance characteristics. Some of the tests can be conducted on fingerpick blood samples, so no opportunity is provided for reflex testing in them. "
    [Show abstract] [Hide abstract] ABSTRACT: Recent approvals of direct-acting, orally delivered pharmaceuticals for the treatment of patients with infection by HCV and of a point-of-care assay for community screening of HCV infection have generated impetus to widen the identification of HCV-infected individuals. Diagnosis of HCV infection is, however, still based on the detection of anti-HCV immunoglobulin G. As treatment is intended for individuals with current infection, testing for evidence of infection would need to centre on the detection of HCV viraemia. Minimizing the complexity and costs associated with HCV nucleic acid testing and speeding the development and validation of HCV antigen assays expedite the identification of HCV-viraemic individuals. Establishing means to diagnose recent HCV infection and to engage in surveillance of drug-resistant HCV are also apposite. Successful implementation of these various measures brightens prospects for the eventual elimination of HCV.
    Full-text · Article · Jan 2012
  • [Show abstract] [Hide abstract] ABSTRACT: Point-of-care tests provide a plausible diagnostic strategy for hepatitis C infection in economically impoverished areas. However, their utility depends upon the overall performance of individual tests. A literature search was conducted using the metasearch engine Mettā, a query interface for retrieving articles from five leading medical databases. Studies were included if they employed point-of-care tests to detect antibodies of hepatitis C virus and compared the results with reference tests. Two reviewers performed a quality assessment of the studies and extracted data for estimating test accuracy. Thirty studies that had evaluated 30 tests fulfilled the inclusion criteria. The overall pooled sensitivity, specificity, positive likelihood-ratio, negative likelihood-ratio and diagnostic odds ratio for all tests were 97.4% (95% CI: 95.9-98.4), 99.5% (99.2-99.7), 80.17 (55.35-116.14), 0.03 (0.02-0.04), and 3032.85 (1595.86-5763.78), respectively. This suggested a high pooled accuracy for all studies. We found substantial heterogeneity between studies, but none of the subgroups investigated could account for the heterogeneity. Genotype diversity of HCV had no or minimal influence on test performance. Of the seven tests evaluated in the meta-regression model, OraQuick had the highest test sensitivity and specificity and showed better performance than a third generation enzyme immunoassay in seroconversion panels. The next highest test sensitivities and specificities were from TriDot and SDBioline, followed by Genedia and Chembio. The Spot and Multiplo tests produced poor test sensitivities but high test specificities. Nine of the remaining 23 tests produced poor test sensitivities and specificities and/or showed poor performances in seroconversion panels, while 14 tests had high test performances with diagnostic odds ratios ranging from 590.70 to 28822.20. Performances varied widely among individual point-of-care tests for diagnosis of hepatitis C virus infection. Physicians should consider this while using specific tests in clinical practice.
    Full-text · Article · Mar 2015
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