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Journal of Clinical Microbiology, June 2008, p. 1914-1918, Vol. 46, No. 6
0095-1137/08/$08.00+0 doi:10.1128/JCM.02332-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Université Paris Descartes, Equipe Immunité et Biothérapie Muqueuse, Unité INSERM Internationale U743 (Immunologie Humaine), Centres de Recherches Biomédicales des Cordeliers and Laboratoire de Virologie, Hôpital Européen Georges Pompidou, Paris, France,1 Laboratoire de Microbiologie, Hôpital Saint-Louis, Paris, France,2 Clinical Research Unit, Department of Infectious and Tropical Diseases, and Infectious Diseases Epidemiology Unit, Department of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, United Kingdom,3 Centre National de Référence des Maladies Sexuellement Transmissibles et du SIDA de Bangui and Unité de Recherches et d'Intervention sur les Maladies Sexuellement Transmissibles et du SIDA, Faculté des Sciences de la Santé, Bangui, Central African Republic,4 West African Project To Combat AIDS and STDs, Accra, Ghana,5 Centre for International Health, University of Sherbrooke, Sherbrooke, Canada6
Received 4 December 2007/ Returned for modification 25 January 2008/ Accepted 21 March 2008
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A critical element in evaluating the performance of these assays is the stage of HSV-2 infection. One study reported that the sensitivity of HerpeSelect increased for patients suffering from genital ulcer disease (GUD) compared to that for blood donors (6), perhaps because HerpeSelect may detect primary genital herpes earlier than the Kalon assay or even WB does (1, 12).
In the present report, we assess the performance characteristics of the HerpeSelect and Kalon assays for African patients presenting with symptomatic and molecularly documented genital HSV-2 infection.
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The Kalon gG2-specific assay (Kalon Biologicals, Aldershot, United Kingdom) was used to test all available sera with HerpeSelect index values ranging from >1.1 to 3.5 (n = 63 of 66 sera), a random selection of 88 sera with index values of >3.5, and 48 sera with index values of <0.9, including all cases (n = 25) of potential HSV-2 seroconverters (as defined above).
We calculated the percentage agreement between the two tests and their concordance by Cohen's kappa coefficient (
), and we tested for differences in positive test results by using McNemar's
2 test for paired samples. Chi-square tests were used to compare proportions for unpaired tests, the Wilcoxon rank sum test was used for comparison of medians, and Spearman's rank test was used for correlation of categorical variables.
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Table 1 shows the distribution of HerpeSelect index values by genital HSV-2 DNA status, combining results from the two countries since no difference in the distributions of HerpeSelect index values was observed (not shown). Serum samples from 346 (80%) women were found to be HSV-2 seropositive by HerpeSelect (index values of >1.1), of which 66 (19%) had low-positive index values (
3.5). Samples from another six women were found to be equivocal (index values of 0.9 to 1.1), with one being associated with positive detection of HSV-2 DNA (in the lesional sample). Overall, 58% (36/62 patients) of women with low-positive HerpeSelect index values and 60% (164/275 patients) of women with high-positive HerpeSelect index values had molecular evidence of genital HSV-2 infection (P = 0.8). Of the 200 HSV-2-seropositive women with genital HSV-2 DNA, 36 (18%) had index values of <3.5. Among HSV-2-seropositive women, there was little difference in median index values between women with (median = 6.8; interquartile range, 4.4 to 10.2) and without (median = 7.8; interquartile range, 4.4 to 10.1) detectable genital HSV-2 DNA (P = 0.50). The frequency of recent clinical episodes was significantly correlated with the HerpeSelect titer. An episode of GUD in the preceding 12 months was reported by 14%, 17%, 26%, and 40% of patients in the groups with negative, equivocal, low-positive, and high-positive HerpeSelect serology, respectively (Spearman's rank correlation; P < 0.0001) (Table 1).
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TABLE 1. Distribution of HerpeSelect gG2 index values according to genital HSV-2 DNA detection in women with GUD in Ghana and the Central African Republic
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= 0.68). All 48 samples found to be negative with HerpeSelect were negative with the Kalon assay. Similarly, all but 1 of the 88 samples with HerpeSelect index values of >3.5 were positive with the Kalon assay. The one discordant sample had a high HerpeSelect index value (6.8), with HSV-2 DNA detection in both lesional and cervicovaginal samples. The combined results of negative samples (index values of <0.9 with both assays) and high-positive samples (index values of >3.5 for HerpeSelect) gave an agreement of 99% (135/136 samples), corresponding to a high kappa coefficient (
= 0.98). |
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TABLE 2. Results of HerpeSelect and Kalon testing according to assay index values
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Assuming detection of genital HSV-2 DNA (n = 34) and/or concordant seropositivity with the Kalon assay (n = 36) as confirmation of HSV-2 infection, 71% (45/63 samples) of samples with HerpeSelect index values between >1.1 and 3.5 should be considered true HSV-2 infections and would have been misclassified using the higher cutoff of 3.5 suggested by Hogrefe et al. (7) and Nascimento et al. (13). Among discordant samples tested for HSV-2 DNA, 40% (10/25 samples) were associated with positive detection of HSV-2 DNA (Table 2). Finally, among women found to be seropositive with HerpeSelect and to have concomitant genital HSV-2 DNA, only 88% (76/86 patients) were considered HSV-2 seropositive with the Kalon assay.
Among the 76 women classified as HSV-2 seronegative or equivocal by HerpeSelect at day 0 who had genital samples, 25 (6% of all women in the trial) had genital HSV-2 DNA detected by PCR (Table 1). These patients presented to the clinics after a median of 6 days (range, 3 to 18 days) following symptom onset. All of these women were HSV-1 seropositive by HerpeSelect gG1 assay and thus were classified as having nonprimary first episodes of genital HSV-2 infection. All day 0 sera were also found to be negative by Kalon assay. Among these women, 15 were tested on either day 14 or day 28 (10 were tested on both days, 3 were tested only on day 14, and 2 were tested only on day 28), and 11 cases of HSV-2 seroconversion were detected, with 10 detected by HerpeSelect and 7 detected by Kalon assay. HSV-2 seroconversion was detected earlier with HerpeSelect than with the Kalon assay (Fig. 1). At day 14, 77% (10/13 samples) of sera were positive with HerpeSelect, compared with only 23% (3/13 sera) with the Kalon assay (P = 0.01). Four additional seroconversions were observed with the Kalon assay at day 28, and none were detected by HerpeSelect. The median HerpeSelect index value for these 10 seroconversion cases was 4.3 (range, 2.1 to 15.9) at day 14 and 8.6 (range, 1.5 to 16.6) at day 28. Among patients with nonprimary first episodes of genital HSV-2 infection, four were HIV seropositive at baseline and one woman seroconverted to HIV seropositive within 28 days. All three HIV-seropositive samples which were tested at day 28 showed HSV-2 seroconversion.
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FIG. 1. Number of cases and timing of HSV-2 seroconversion by HSV-2 serological assay among 15 patients with first episodes of genital HSV-2 infection in Ghana and the Central African Republic. On day 14, 13 women were tested. For day 28, the number of seroconversion cases corresponds to the cumulative number of seroconverters on days 14 and 28. Results of HerpeSelect are presented in black bars, and results of the Kalon assay are shown with gray bars.
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Our results show 99% concordance between the HerpeSelect and Kalon assays for negative or high-positive (>3.5) HerpeSelect results, which confirms previous reports of excellent agreement between these two assays (13, 16). In contrast, the concordance was moderate when HerpeSelect positivity included index values between >1.1 and 3.5. However, we found that 40% (10/25 samples) of discordant samples were associated with detection of genital HSV-2 DNA, and 71% of samples with low-positive HerpeSelect index values could be classified as having established HSV-2 infection when results of molecular testing or seroconcordance were included. Overall, nearly 20% of the study population with positive HerpeSelect serology had index values comprising between >1.1 and 3.5, 58% of whom had evidence of genital HSV-2 infection. This is consistent with data published by Ashley-Morrow et al. showing that 22% of U.S. patients with established HSV-2 infection had low HerpeSelect index values (3). Reciprocally, 18% of women testing positive by HerpeSelect and carrying genital HSV-2 DNA had low HerpeSelect index values. These findings demonstrate that a nonnegligible proportion of true genital herpes cases would be missed by using a higher cutoff for HerpeSelect.
The analysis of the kinetics of HSV-2 antibodies in sera associated with nonprimary first clinical episodes of HSV-2 infection showed that HerpeSelect detected HSV-2 seroconversion more frequently and earlier than did the Kalon assay and that HerpeSelect index values increased rapidly. These results corroborate data from the work of Ashley-Morrow et al. (3) demonstrating that for newly infected patients, HerpeSelect index values start low, often in the negative range, and peak a median of 9 to 10 weeks later. Our results also confirm the higher sensitivity of HerpeSelect than that of the Kalon assay in detecting nonprimary first HSV-2 episodes, as previously reported (12). In a U.S. study including 14 patients with nonprimary first episodes with culture-positive HSV-2 lesions, the sensitivity of HerpeSelect was 77%, in contrast to 43% for the Kalon assay, and the median time for seroconversion was significantly longer by Kalon assay (149 days) than by HerpeSelect (22 days) (12). In our study, patients with nonprimary first episodes of HSV-2 infection presented to the clinics after a median of 6 days (range, 3 to 18 days) following symptom onset, and thus the maximum follow-up time to assess seroconversion was 46 days postonset, which explains the higher detection rate obtained with HerpeSelect. We also found that HerpeSelect seropositivity and index values correlated with reported GUD symptoms in the preceding year. These results suggest that frequent viral reactivations may sustain specific humoral responses and, conversely, that low titers may be related to insufficient antigenic stimulation secondary to infrequent viral replication, as suggested by Ashley-Morrow et al. (3).
Thus, the ability of methods to detect early HSV-2 infection may account for some of the assay discrepancies found in our and other studies. It is even possible that some recent HSV-2 infections may have been accompanied by a lack of HSV-2 DNA detection, since the delay between the onset of symptoms and presentation at the clinic for study enrollment was quite long for some women, allowing some patients to have already cleared the virus. Such misclassifications would have contributed to underestimating the true sensitivity of HerpeSelect.
We did not use the reference WB HSV assay in this study to help resolve some of the assays' discrepancies. However, it has been shown that although it is highly sensitive and specific, WB may have less ability to detect recent cases of genital herpes, as detection of seroconversion among first episodes of genital HSV-2 infection was slower than that of HerpeSelect (1). Moreover, it has been shown that some discordant results between HerpeSelect and WB on African sera were eventually classified as true positive results by HerpeSelect after testing with an inhibition assay (7).
Finally, our data did not support a differential performance of HerpeSelect according to HIV serostatus. On the contrary, we observed less discrepancy between the HerpeSelect and Kalon assays for samples from HIV-infected women. This may be related to the higher rate of HSV-2 reactivation in such patients, which might sustain index values of HSV-2-specific antibodies in the high range.
Our results confirm that some low-positive HerpeSelect index values correspond to true HSV-2 infection and that some may be related to recent infection. Depending on population composition, this would affect the evaluation of the performance of the various HSV-2 serological assays, and this has to be taken into consideration in the interpretation of study findings. Moreover, the choice of HSV-2 serological assays needs to be dictated by circumstances, whether for an epidemiological study examining risk factors for HSV-2 or a clinical trial seeking to enroll HSV-2-seropositive patients, for which highly specific assays would be more desirable, or for the diagnosis and management of patients with possible early HSV-2 infection, for which a sensitive assay would be required. Our results have particular resonance for the management of GUD in countries where HSV-2 infection is highly prevalent and where clinical or subclinical primary infection may occur frequently. The use of a sensitive assay comparable to HerpeSelect may help to detect recent herpesvirus infection and offer appropriate advice on management and counseling about the risk of HIV acquisition, which could increase in the presence of recent HSV-2 infection (4, 15).
Published ahead of print on 2 April 2008. ![]()
The composition of the ANRS 12-12 Study Group is detailed in Acknowledgments. ![]()
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