Criteria to Screen Molecular Tests for the Diagnosis of Herpes Simplex Virus in the Central Nervous System have no Propensity to Harm

Rational Use of Microbiological Tests in the Diagnosis of Central Nervous System Infections Using Restrictive Criteria: a Retrospective Study

Microbiological testing in general and in the setting of central nervous system (CNS) infection in particular are often excessive, leading to superfluous laboratory work and costs. In this regard, restrictive criteria, named Reller criteria, have been developed to reduce unnecessary CSF herpes simplex virus 1 (HSV-1) PCR testing when suspecting encephalitis.

Assessment of Diagnostic Yield of Nonculture Infection Testing on Cerebrospinal Fluid in Immune-Competent Children

IMPORTANCE

Nonculture infection tests of cerebrospinal fluid (CSF) samples using polymerase chain reaction and antigen or antibody assays are frequently ordered on lumbar puncture specimens concurrently with routine CSF cell counts, but the value of CSF infection testing in otherwise healthy children is unknown.

OBJECTIVE

To determine the value of nonculture CSF infection testing in immune-competent children with normal CSF cell counts.

DESIGN, SETTING, AND PARTICIPANTS

This cross-sectional study reviewed screening and diagnostic tests in the electronic medical record system of a large academic tertiary care children's hospital. Records of children aged 0.5 to 18.9 years (n = 4083) who underwent lumbar puncture (n = 4811 procedures) in an inpatient or outpatient facility of Children's Hospital of Philadelphia between July 1, 2007, and December 31, 2016, were reviewed. Those with indwelling CSF shunts or catheters; those with active or past oncologic, immunologic, or rheumatologic conditions; or those taking immune-suppressing medications were excluded from analysis. This study was conducted from July 20, 2017, to March 13, 2019.

MAIN OUTCOMES AND MEASURES

Outcome variables included frequency of nonculture CSF infection testing and frequency of positive results in the entire cohort, and among those with normal cell counts. Normal cell counts were defined as CSF white blood cell counts lower than 5 cells/μL and CSF red blood cell counts lower than 500 cells/μL.

RESULTS

In total, 4811 lumbar puncture procedures were performed on 4083 unique children, with a median (range) age of 7.4 (0.5-18.9) years, 2537 boys (52.7%), and 3331 (69.2%) with normal CSF cell counts. At least 1 nonculture CSF infection test was performed on 1270 lumbar puncture specimens with normal cell counts (38.1%; 95% CI, 36%-40%), and more tests were performed in the summer months. Only 18 (1.4%; 95% CI, 0.9%-2.2%) of 1270 lumbar puncture specimens with normal cell counts had at least 1 nonculture infection test with a positive result; 2 of these 18 children required clinical intervention for their positive results, but each also had other clear clinical signs of infection.

CONCLUSIONS AND RELEVANCE

Nonculture CSF infection testing appeared to be common in immune-competent children with normal CSF cell counts, but positive results were uncommon and were not independently associated with clinical care; delaying the decision to send nonculture infection tests until CSF cell counts are available could reduce unnecessary diagnostic testing and medical costs, which may improve value-based care.

Laboratory Diagnosis of Neonatal Herpes Simplex Virus Infections

Herpes simplex virus (HSV) is a common and often benign infection in humans; although it less commonly affects newborns, infection in this age group can be devastating. Newborns often present with nonspecific clinical findings, making timely and accurate diagnosis of infection critical. A wide variety of tests are available for detecting herpes simplex virus infection, but only a subset are useful and validated in the newborn population. The current review summarizes available diagnostic testing for neonatal disease, including discussing limitations, unmet needs, and emerging data on molecular testing methods.

Missing Cases of Herpes Simplex Virus (HSV) Infection of the Central Nervous System When the Reller Criteria Are Applied for HSV PCR Testing: a Multicenter Study

Previous studies suggested that herpes simplex virus (HSV) PCR testing can be safely deferred in patients with normal cerebrospinal fluid (CSF) white blood cell (WBC) counts and protein levels as long as they are older than 2 years of age and are not immunocompromised, the so-called Reller criteria. In this multicenter study, we retrospectively assessed the validity of these screening criteria in our setting. A total of 4,404 CSF specimens submitted for HSV PCR testing to the respective microbiology laboratories at the participating hospitals between 2012 and 2018 were included. Six commercially available HSV PCR assays were used across the participating centers. Ninety-one of the 4,404 CSF specimens (2.1%) tested were positive for HSV DNA (75 samples for HSV-1 and 16 for HSV-2). Nine patients failed to meet the Reller criteria, of whom seven were deemed to truly have HSV encephalitis. Overall, no significant correlation between HSV PCR cycle threshold (C_T ) values and WBC counts or total protein levels was found. In addition, median HSV PCR C_T s were comparable between patients who met the Reller criteria and those who did not (P = 0.531). In summary, we show that HSV DNA may be detected in CSF specimens with normal WBC and protein levels collected from immunocompetent individuals older than 2 years with HSV encephalitis. Nevertheless, the data also indicate that the number of cases detected could be lowered at least by half if CSF specimens with borderline WBC counts (4 cells/mm³) as well as children of any age are systematically tested.

Cost-Effectiveness Study of Criteria for Screening Cerebrospinal Fluid To Determine the Need for Herpes Simplex Virus PCR Testing

The absence of markers of inflammation in the cerebrospinal fluid (CSF) commonly predicts the absence of herpes simplex virus (HSV) central nervous system (CNS) infection. Consequently, multiple authors have proposed and validated criteria for deferring HSV PCR testing of CSF in immunocompetent hosts with normal CSF white blood cell and protein levels (≤5 cells/mm³ and ≤50 mg/dl, respectively). Hosts are considered immunocompetent if they are ≥2 years old and have not had HIV or an organ transplant. Adoption of the criteria may erroneously exclude HSV-infected persons from a necessary diagnostic test or, alternatively, reduce the costs associated with HSV tests with minimal to no effect on patient care. Little is known about the cost-effectiveness of this approach. A decision analysis model was developed to evaluate the adoption of criteria for screening HSV tests of CSF. Estimates of input parameter values combined available literature with a multiyear multisite review at two of the largest health care systems in the United States. Adoption of criteria to screen for HSV test need proved cost-effective when less than 1 in 200 patients deferred from testing truly had an HSV CNS infection. Similar to prior studies, none of the deferred cases had HSV encephalitis (n = 3120). Adoption of these criteria in the United States would save an estimated $127 million ($95 million to $158 million [±25%]) annually. The model calculations remained robust to variation in test cost, prevalence of HSV infection, and random variation to study assumptions. The adoption of criteria to screen HSV PCR tests in CSF represents a cost-effective approach.