Disclosure: Dr. Talan is a paid consultant for BioFire Diagnostics and has advised on the development of new assays and collaborative research on meningitis and septic arthritis.
Explore This IssueACEP Now: Vol 39 – No 03 – March 2020
Back in the 1980s, texts stated that the administration of antibiotics should not be delayed beyond 30 minutes in cases of suspected bacterial meningitis. Doctors who weren’t fast enough were being sued.
This never seemed practical or possible. In fact, my very first research study from that time assessed time from triage to antibiotics for 122 ED patients admitted for presumed bacterial meningitis.1
We found that the median time to the first dose of antibiotics was three hours and that only one patient received antibiotics within 30 minutes. We also found that diagnosis was not always obvious based on so-called classic symptoms. The reality was that patients presented with a range of complaints compatible with not only meningitis but also other diagnoses. The process of sorting that out could take time. “Delays” came not from laziness or lunch breaks but from the necessity of a proper diagnostic investigation.
Decades later, the diagnostic pathway for meningitis has changed little. The only significant change is the ability to obtain a pre-lumbar puncture (LP) CT of the brain nearly instantaneously. This lessens the angst of deferring antibiotics until the post-CT LP is completed, allowing for unambiguous bacterial identification and susceptibly testing.
However, we’ve recently seen an advance in the diagnostic pathway for meningitis as more hospital labs offer rapid molecular testing of the cerebrospinal fluid (CSF) for emergency department use. The BioFire FilmArray Meningitis/Encephalitis Panel detects nucleic acids from common bacterial and viral pathogens with a high degree of accuracy, providing results within one to two hours (see Table 1).2 Currently, the BioFire CSF assay is the only FDA–approved molecular test available that detects a full range of pathogens.
There are several test features that will improve management of ED patients with suspected meningitis.
Confident Diagnoses Reduces Hospital Admissions
Viral meningitis is far more common than bacterial meningitis. Because of the imperfect accuracy of standard CSF results in discriminating bacterial versus viral causes (particularly for patients pretreated with antibiotics), patients with a low likelihood of bacterial meningitis are often hospitalized for observation while awaiting final CSF culture results. The BioFire assay can confirm viral meningitis—most commonly due to enterovirus (EV) or other viruses. This can allow confident ED discharge. (Little-known fact: As many as 30 percent of patients found to have EV meningitis by molecular testing have normal CSF parameters.) Human herpesvirus-6 (roseola), the most common viral cause of childhood febrile seizures, is also included in the assay. The panel does not test for all possible viral pathogens (eg, flu, HIV), which account for a small number of cases.
Ruling in viral causes is one thing, but what about ruling out bacterial ones? Even when the test does not affirmatively identify a virus, in a clinically stable, non-immunocompromised patient presenting with acute symptoms, a negative CSF molecular panel should be reassuring enough to permit ED discharge, provided the patient received no prior antibiotics and has low-risk CSF parameter findings. The BioFire assay has near-perfect sensitivity to rule out typical bacterial meningitis pathogens. Of course, there are also noninfectious causes of meningitis to consider (eg, cancer, lupus, medication reactions, etc.) and symptoms of viral meningitis can last weeks. Patients should have close primary care follow-up to make sure that subacute but nonemergent problems do not go undiagnosed.