Meningitis / Encephalitis

Neonatal Herpes Part 2 – Testing and Diagnosis

Published on 27 Aug 2020

Part 1 of this series addressed the clinical background of neonatal herpes infection including a case study. Part 2 will discuss clinical testing and diagnosis of the condition.

For antiviral therapy to be initiated, physicians must have a level of suspicion of neonatal HSV infection. Definitive diagnosis of neonates is often difficult, as highlighted earlier in part 1 of this series, neonatal herpes can present with a wide range of clinical presentations, many of which could also be associated with other neonatal conditions.1 Furthermore, not all neonatal herpes infections presents with skin lesions, which could otherwise facilitate diagnosis of HSV infection.  Therefore, in addition to clinical assessment, infants suspected with neonatal herpes require a number of tests in order to be appropriately diagnosed. These include medical imaging and laboratory testing of blood, urine, skin swabs, eyes, and cerebrospinal fluid fluid (CSF).

Viral culture has been the traditional method for detecting HSV from patient samples. However, over the last decade, there has been a shift in replacing culture with polymerase chain reaction (PCR) detection, which is rapidly becoming the standard methodology for HSV detection. Many of the limitations of viral culture such as time to result, viability of specimen and clinical performance can be overcome with PCR.

Although there are a number of IVD PCR assays available for HSV detection, many of these tests are not well suited for neonatal herpes diagnosis. Such PCR tests are primarily designed with adult HSV infections in mind, which are intended for use with sample types related to genital or oral herpes only. In contrast, neonatal herpes can manifest in the central nervous system (CNS) and usually requires a lower limit of detection for optimal clinical sensitivity. Furthermore, many PCR tests are not validated for clinical performance on a pediatric population.

An ideal PCR assay for neonatal herpes testing would therefore require the following2:
1 – Validation for a pediatric population, particularly those less than 1 month old.
2 – Validation for mucocutaneous swabs, cutaneous swabs and CSF sample types.
3 – Proven clinical sensitivity, especially for CNS applications.

References
1. Gant M (2018 July 19) Fox News. Parents whose newborn babies died from herpes warn about deadly virus, Retrieved from https://www.foxnews.com/health/parents-whose-newborn-babies-died-from-herpes-warn-about-deadly-virus
2. Data on file for the Simplexa HSV 1 & 2 Direct kit, HSV clinical study validation report.

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