The clinical management of suspected herpes virus encephalitis. A decision-analytic view.

This study addresses the issues of brain biopsy and adenine arabinoside (Ara-A) therapy in the clinical management of patients suspected of having herpes simplex virus encephalitis (HVE). The analysis does not speak to experimental studies in which brain biopsy and new therapies are justified by investigational goals outside the scope of this analysis. Decision analytic techniques are used, employing published quantitative data and subjective estimates of probabilities provided by experts in the management of this condition. In patients with features indicative of a high likelihood of HVE--evidence of acute encephalopathy, focal cerebral signs, objective evidence of localization and cerebrospinal-fluid findings compatible with viral infection--a strategy of treating with Ara-A without brain biopsy is consistent with optimal survival under current central estimates for mortality at biopsy, therapeutic effectiveness, drug toxicity, and sensitivity and specificity of brain biopsy. This results depends primarily upon the apparent low toxicity of Ara-A, the relatively high likelihood of HVE in typical clinical presentations and the presence, although at a low rate, of falsely negative biopsy reports expected in the disease. Sensitivity analyses are presented to explore the effects of changes in estimates of values for important variables on the choice of a strategy for clinical management. The analysis provides a structure for assessing the clinical significance of new information on such relevant variables as drug toxicity, biopsy sensitivity and mortality, and the yield of treatable new conditions other than HVE diagnosed by brain biopsy.