Herpes simplex encephalitis: an audit of the use of laboratory diagnostic tests.
BACKGROUND
The combination of both PCR and intrathecal antibody studies is recommended to confirm or refute the diagnosis of herpes simplex encephalitis (HSE).


OBJECTIVE
To investigate the pattern of use of laboratory tests in the diagnosis of suspected cases of HSE, and to determine the final diagnosis in cases proven not to be HSE.


METHODS
Structured audit.


METHODS
We reviewed the case-notes of all patients who, over a five-year time period, presented with suspected encephalitis; and/or were prescribed aciclovir. Clinical and laboratory criteria were used to categorize the likelihood of HSE.


RESULTS
We identified 222 patients: 10 (5%) had definite HSE, 24 (10%) possible HSE, and 144 (65%) a definite alternative diagnosis. In 44 (20%), no final diagnosis was made, but the diagnosis of HSE was excluded. PCR was performed in 68 (31%), intrathecal antibody studies in 24 (11%), and brain biopsy in 17 (8%). A wide range of diseases mimicked HSE, but most common were inflammatory diseases and other infections of the central nervous system.


CONCLUSIONS
Laboratory tests, particularly intrathecal antibody assays, are under-used in the diagnosis of HSE. Although early empirical treatment of suspected HSE is essential, confirmation or exclusion of the diagnosis is equally important to avoid overlooking alternative diagnoses. Identification of the aetiology of encephalitis is of particular importance, given the current concerns of emerging infections and bioterrorism.
Chataway
J
J
Departments of Neurology, The National Hospital for Neurology and Neurosurgery, London, UK. jeremy.chataway@st-marys.nhs.uk
Davies
N W S
NW
Farmer
S
S
Howard
R S
RS
Thompson
E J
EJ
Ward
K N
KN
D000212:Acyclovir / Q000627:therapeutic use; D000914:Antibodies, Viral / Q000032:analysis; D000998:Antiviral Agents / Q000627:therapeutic use; D001921:Brain / Q000276:immunology; D003937:Diagnosis, Differential; D020803:Encephalitis, Herpes Simplex / Q000134:cerebrospinal fluid / Q000175:diagnosis* / Q000188:drug therapy; D005814:Genes, Viral; D006801:Humans; D008485:Medical Audit / Q000379:methods*; D016133:Polymerase Chain Reaction / Q000379:methods; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D018139:Simplexvirus / Q000235:genetics
D000914:Antibodies, Viral; D000998:Antiviral Agents; D000212:Acyclovir