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Herpes simplex virus type-2 (HSV-2) infection is one of the most common sexually transmitted infections, with a significantly increased incidence worldwide. Effective intervention has been complicated, in part, by the absence of methods to differentiate HSV-1- from HSV-2-infected individuals accurately and easily. During the past 15 years, many tests for detecting antibodies to HSV-1 or HSV-2 have been developed. The recent article by Ashley-Morrow et al.[1] described the performance of the HerpeSelect HSV-2 ELISA (Focus Technologies, Cypress, CA, USA) in ten different geographical locations. This test has been introduced into sexually transmitted disease (STD) services in China, and has also been used in epidemiological and interventional projects.

In order to determine the performance, and particularly the sensitivity and specificity, of the Focus HSV-2 ELISA in Chinese STD settings, 105 serum specimens were collected from patients attending the STD Clinic of the Chinese Academy of Medical Sciences, and the Peking Union Medical College Institute of Dermatology. The results obtained with the Focus HSV-2 ELISA were compared with those determined by the Western blot method.

The seroprevalence of HSV-2, as determined by Western blot, was 55.2% (58/105 specimens) in the study population. The Focus HSV-2 ELISA and Western blot results were concordant (both negative or both positive) for 89.5% of the 105 specimens, with 92.0% sensitivity and 95.7% specificity, and positive and negative predictive values of 95.8% and 91.7%, respectively, if specimens with equivocal ELISA results were excluded from the calculation. The sensitivity and specificity were 79.3% and 95.7%, respectively, if the samples with equivocal ELISA results were considered negative, and were 93.1% and 93.6%, respectively, if the samples with equivocal ELISA results were considered positive. Analysis with a receiver operator characteristic curve demonstrated that the best index cut-off value to optimise the assay performance in this population was 0.9, with a sensitivity of 93.1% (95% CI, 83.3–98.0%) and a specificity of 93.6% (95% CI, 82.4–98.6%). If the manufacturer's recommended index cut-off value of 1.1 was used, the sensitivity was only 79.3%.

In summary, the sensitivity and specificity of the Focus HSV-2 ELISA in a Chinese STD population were satisfactory but, compared with other countries, a lower index cut-off value might be required for optimal sensitivity and specificity.

Acknowledgement

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This study was supported by the National Natural Science Foundation of China (grant no. 30170857).

Reference

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