Polymerase chain reaction for detection of herpes simplex virus encephalitis

Viruses in the Intensive Care Unit (ICU)

Whereas viruses are not usually considered to be important causes of ICU admission this review has demonstrated this perception to be incorrect. Viruses and their manifestations differ from continent to continent and hemisphere to hemisphere and it is essential that the intensivist be familiar with diagnosis and management of these ubiquitous organisms.

Use of the polymerase chain reaction in the diagnosis of herpes simplex encephalitis: a decision analysis model

PURPOSE

To evaluate the utility of an assay based on a polymerase chain reaction (PCR) of cerebrospinal fluid in the management of patients with suspected herpes simplex encephalitis.

METHODS

A decision model was constructed and used to compare a PCR-based approach with empiric therapy. Inputs required by the model included the sensitivity (96%) and specificity (99%) of PCR (derived from review of the literature), the prevalence of herpes simplex encephalitis (5%, based on the actual prevalence at Barnes Hospital among patients treated empirically with acyclovir), the outcomes for patients with and without herpes simplex encephalitis (derived from clinical studies of the Collaborative Antiviral Study Group and the actual experience at Barnes Hospital), and the average duration of empiric acyclovir therapy for patients with possible herpes simplex encephalitis (5.3 days based on actual experience at Barnes Hospital).

RESULTS

Using these input values, the decision model predicted better outcomes with empiric therapy. However, low rates of inappropriate discontinuation of empiric therapy in patients with herpes simplex encephalitis or improved diagnosis and outcome resulting from a negative PCR assay result in patients without herpes simplex encephalitis led to better outcomes with the PCR-based approach. The PCR-based approach was associated with 9.2 fewer doses of acyclovir per patient.

CONCLUSION

Based on the decision model using conservative assumptions, a PCR-based approach can yield better outcomes and reduced acyclovir use compared with empiric therapy.