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Clinical and Vaccine Immunology, May 2008, p. 888-890, Vol. 15, No. 5
1071-412X/08/$08.00+0 doi:10.1128/CVI.00453-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.
Improved Performance of Enzyme-Linked Immunosorbent Assays and the Effect of Human Immunodeficiency Virus Coinfection on the Serologic Detection of Herpes Simplex Virus Type 2 in Rakai, Uganda
Jordyn L. Gamiel,1
Aaron A. R. Tobian,2
Oliver B. Laeyendecker,1,3
Steven J. Reynolds,1,3
Rhoda Ashley Morrow,4
David Serwadda,5
Ronald H. Gray,6 and
Thomas C. Quinn1,3*
Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland,1
Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland,2
National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland,3
Department of Laboratory Medicine, University of Washington, Seattle, Washington,4
Institute of Public Health, Makerere University, Kampala, Uganda,5
Department of Population, Family and Reproductive Health Sciences, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland6
Received 29 October 2007/
Returned for modification 28 January 2008/
Accepted 21 February 2008

ABSTRACT
Ugandan subjects (820) were tested by Focus HerpeSelect enzyme-linked
immunosorbent assay (ELISA), Kalon herpes simplex virus type
2 ELISA, and BioKit rapid test, and the results were compared
to those of Western blotting. Higher-than-standard-index cutoff
values gave optimal sensitivity and specificity. Kalon ELISA
was the optimal assay when an index value of 1.5 was used (sensitivity,
91.7%; specificity, 92.4%).

TEXT
Herpes simplex virus type 2 (HSV-2) infection is one of the
most common sexually transmitted diseases, and HSV-2 is the
main cause of genital ulceration worldwide (
4,
5,
17). Genital
HSV-2 infections are associated with an increased risk for acquiring
human immunodeficiency virus type 1 (HIV-1) (
5). Diagnosis of
HSV-2 infection in sub-Saharan Africa and developing countries
elsewhere, where the prevalence is high, has been problematic.
Serologic tests for HSV-2 that use an enzyme-linked immunosorbent
assay (ELISA) or dot blot are technically simple and relatively
inexpensive (
15) but have been complicated by a variable rate
of samples with positive HSV-2 ELISA and negative Western blot
results (
6,
8,
10,
15). In addition, the Western blot assay
is expensive, difficult to read, and inefficient for evaluating
large numbers of samples for clinical trials (
2). We and others
have previously demonstrated that a higher index cutoff value
is required for optimal sensitivity and specificity for the
Focus HerpeSelect HSV-2 ELISA (
3,
10); however, the assay still
lacks specificity. Therefore, Focus HerpeSelect ELISA, Kalon
HSV-2 ELISA, and BioKit rapid test were compared to Western
blotting as the gold standard.
The study utilized sera from 820 subjects (273 HIV positive and 547 HIV negative) collected in a population-based randomized control trial of presumptive sexually transmitted disease treatment among adults aged 15 to 19 in Rakai District, Uganda, from 1994 to 1998 (7, 10). All relevant institutional review boards in Uganda and at Johns Hopkins University and the National Institutes of Health approved the trial. Samples were collected at the participant's home, processed for sera, and stored at –70°C. The University of Washington HSV-2-specific Western blot analysis was performed as previously described (1, 12). The Focus HerpeSelect HSV-2 ELISA (Focus Technologies, Cypress, CA) and Kalon ELISA (Kalon Biological Ltd., Guilford, United Kingdom) were performed according to the manufacturers' protocols (11) with a few modifications. Samples and controls were run in either triplicate (Focus) or duplicate (Kalon). Mean index values were used for all calculations. Any samples with discordant results were run again. The Sure-Vue HSV-2 rapid test (BioKit USA Inc., Lexington, MA) was performed according to the protocol for serum samples. HIV status was determined using two different ELISAs (the Vironostika HIV-1 [Organon Teknika, Charlotte, NC] and one from Cambridge Biotech, Worcester, MA). Discordant results or new seroconversions were confirmed by HIV-1 Western blot assay (bioMerieux-Vitek, St. Louis, MO), as previously described (7). Statistical calculations and receiver operating characteristic curves were performed using Intercooled Stata 9.2 (StataCorp LP, College Station, TX).
To evaluate the performance of Focus HerpeSelect ELISA in detecting HSV-2 seroprevalence in sub-Saharan Africa, 820 subjects were tested. According to the manufacturer's instructions (index cutoff value, 1.1), the test had a sensitivity of 99.0% and a specificity of 50.7%. An index cutoff value of 3.2 was determined to provide the optimal sensitivity (88.4%) and specificity (80.8%).
Of the 820 subjects, 538 were also evaluated by Kalon ELISA. According to the manufacturer's instructions (index cutoff value, 1.1), the test had a sensitivity of 95.1% and a specificity of 87.6% (Table 1). An index value cutoff of 1.5 gave the optimal sensitivity (91.7%) and specificity (92.4%) (Table 1). The receiver operating characteristic curve demonstrated that Kalon was superior to Focus, with a greater area under the curve (Fig. 1).
Of the 820 subjects, 524 were also evaluated with the BioKit
rapid point-of-care test. According to the manufacturer's instructions,
which indicated that low-positive results should be considered
positive, the sensitivity was 95.8% and the specificity was
56.1%. Adjustment of index values was not possible for this
assay.
Due to the association between HIV-1 and HSV-2 (5, 13, 14), it is important to determine the effect of HIV-1 infection on HSV-2 antibody detection. For both ELISAs and the BioKit assay, there were higher proportions of subjects positive for HSV-2 among the HIV-1-infected than among the uninfected populations (P < 0.001). However, none of the assays were significantly affected by HIV-1 status (Table 2).
This study represents the largest investigation of the performances
of three different commercial HSV-2 assays in sub-Saharan Africa.
We demonstrated that the Kalon HSV-2 immunoglobulin G ELISA
was improved at a higher index cutoff value of 1.5 than for
subjects from the Western hemisphere and is superior to both
the Focus HerpeSelect ELISA and the BioKit rapid point-of-care
antibody test. In addition, we found that HIV status does not
significantly affect the HSV-2 serologic diagnosis.
While adjusting the index values of the assays for subjects from sub-Saharan Africa significantly improved both the sensitivity and specificity, there were still both false-negative and false-positive results. The false negatives could have been due to an early infection, in which case the University of Washington HSV-2-specific Western blot was more sensitive. The false positives might have been due to cross-reactivity with HSV-1, which is >90% prevalent in sub-Saharan Africa (9, 16).
To create the best predictive testing strategy based on sensitivity and specificity compared to the University of Washington HSV-2-specific Western blot assay, different algorithms were analyzed. The optimal testing method with the highest combined sensitivity and specificity was to use the Focus ELISA with an index cutoff value of 1.1 and then test all positive samples with the Kalon ELISA, using an index cutoff value of 1.5. The sensitivity and specificity were then 92.0% and 92.8%, respectively. While this algorithm produced the best results overall, the results were not statistically significantly different from those using the Kalon test alone with a cutoff value of 1.5 (P = 0.7). Overall, the quickest, most economical, and most accurate method for HSV-2 detection was the Kalon ELISA but with an index cutoff higher than the manufacturer's recommendation.

ACKNOWLEDGMENTS
We are grateful to the study participants, whose commitment
and cooperation made this study possible. We also appreciate
help with statistical analysis from Melissa Riedesel and Thoai
Ngo.
This study was supported by the Intramural Research Program of the National Institute of Allergy and Infectious Diseases.

FOOTNOTES
* Corresponding author. Mailing address: Ross Building 1159, 720 Rutland Ave., Baltimore, MD 21205. Phone: (410) 955-3151. Fax: (410) 614-9775. E-mail:
tquinn{at}jhmi.edu 
Published ahead of print on 5 March 2008. 

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Clinical and Vaccine Immunology, May 2008, p. 888-890, Vol. 15, No. 5
1071-412X/08/$08.00+0 doi:10.1128/CVI.00453-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.
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