Validation of Laboratory Screening Criteria for Herpes Simplex Virus Testing of Cerebrospinal Fluid

Abstract

Most patients with herpes simplex virus (HSV) central nervous system (CNS) infection have abnormalcerebrospinal fluid (CSF) indices. Therefore, we implemented screening criteria based on CSF values and host immune status to guide testing. All CSF samples submitted for HSV PCR analysis from January 1999 through December 2004 were included in the study. Specimens from patients with human immunodeficiency virus, a history of transplants, an age of <2 years, a CSF white blood cell count of >5 cells/mm 3 , or a protein level of >50 mg/dl were tested upon request. All other samples were rejected and frozen. To validate our screening criteria, rejected specimens were pooled and tested retrospectively. Electronic medical records were also reviewed. A total of 1,659 HSV PCR requests from 1,458 patients were screened. Of the 1,296 specimens (78.1%) accepted for testing, 1,213 were negative, 7 were positive for HSV type 1 (HSV-1), 26 were positive for HSV-2, and 50 had unavailable results. Sixteen requests were rejected because an alternative microbiologic diagnosis had been established. Of the 347 samples rejected based on criteria, 222 (64.0%) remained available for pooled testing. No HSV-1-positive samples were identified in the rejected specimens. Two rejected specimens tested positive for HSV-2 DNA, but both met acceptance criteria which had not been communicated to the laboratory. Few patients (7.8%) with rejected specimens were treated with acyclovir, which suggests a low clinical concern for HSV encephalitis. Acceptance criteria based on CSF parameters and host immune status saved time and cost and did not miss patients with HSV CNS infection. Communication between the clinician and the laboratory is imperative for a successful screening program.Early recognition of herpes simplex virus (HSV) encephalitis is crucial because prompt initiation of antiviral therapy improves clinical outcomes (17, 18). The detection of HSV DNA directly in cerebrospinal fluid (CSF) by PCR has been well validated for the diagnosis of herpes central nervous system (CNS) infections, and given its high sensitivity and specificity, HSV PCR is now recognized as the reference standard (1,4,9,12). HSV PCR has become one of the most commonly requested tests of CSF in our clinical microbiology laboratory, and there has been a costly trend toward overusing molecular diagnostics to evaluate patients with nonspecific complaints.Most patients with CNS infections have an elevated CSF leukocyte count and/or protein level (5,7,16). Screening the CSF cell count and protein values prior to performing HSV PCR has been suggested as a way to save healthcare costs without reducing sensitivity (13, 16). In addition, laboratory acceptance criteria for HSV testing of CSF have been shown to increase the proportion of positive results (from 1.9% to 4.0% at one institution) (13). Based on these findings, we implemented criteria for HSV PCR testing that are founded on CSF profiles in addition to host characteristics but had not previously been validated with our pro...

PCR for Detection of Herpes Simplex Virus in Cerebrospinal Fluid: Alternative Acceptance Criteria for Diagnostic Workup

“…Our screening criteria for HSV PCR in CSF specimens, which are stricter than those of Hanson et al (5), are very sensitive and allow a significant further reduction in laboratory workload.…”

“…Of the 268 samples rejected based on our criteria, we identified 74 (27.6%) with leukocyte counts of Ͼ5 cells/mm 3 and/or protein levels of Ͼ50 mg/dl that would have met the criteria of Hanson et al (5). Of these 74 samples, 70 (94.6%) remained available for HSV PCR analysis.…”

“…Acceptance criteria based on elevated CSF leukocyte counts (Ͼ5 cells/mm 3 ) and protein levels (Ͼ50 mg/dl) have been proposed as a way to save health care costs without reducing sensitivity (4,5); however, other acceptance criteria have not been evaluated.…”

“…The CSF leukocyte counts reported in previous studies (1,2,(5)(6)(7)(8)(9)(10)(11)(12)(13) are summarized in Table 1. In our institution, we accepted CSF specimens for HSV PCR testing if they had Ͼ10 cells/mm 3 .…”

Clinical Validation of a New Triplex Real-Time Polymerase Chain Reaction Assay for the Detection and Discrimination of Herpes simplex Virus Types 1 and 2

“…This is in agreement with other studies that reported positivity rates from 2.5 to 5% for CSF in a clinical setting. 15,16 In contrast, the positivity rate was much higher for samples from skin and genital lesions (almost 50%) and also for respiratory samples (30%). When respiratory samples were further differentiated, BAL specimens as samples from the lower respiratory tract had less than half of the positivity rate of other respiratory samples, which originated from the upper respiratory tract (20% versus 50%).…”