New Xpert EV Test to Distinguish Between Viral and Bacterial Meningitis

New Xpert EV Test to Distinguish Between Viral and Bacterial Meningitis

Meningitis is the inflammation of the coverings of the brain and/or spinal cord, which consist of the PIA MATER; ARACHNOID; and DURA MATER. Infections (viral, bacterial, and fungal) are the most common causes of this condition, but subarachnoid hemorrhage ( HEMORRHAGES, SUBARACHNOID), chemical irritation (chemical MENINGITIS), granulomatous conditions, neoplastic conditions (e.g., carcinomatous meningitis), and other inflammatory conditions may produce this syndrome.

Several different bacteria can cause meningitis and Neisseria meningitidis is one of the most important because of its potential to cause epidemics.Bacterial meningitis is an infection of the meninges (the covering of the brain and spinal cord). Children with meningitis often have sudden symptoms of fever, headache, and neck stiffness. Children may also have nausea, vomiting, and a worse headache when in a lighted area. They may become confused or difficult to awaken. Meningitis can resemble a bad case of the flu.

The bacteria are transmitted from person to person through droplets of respiratory or throat secretions. Close and prolonged contact (e.g. kissing, sneezing and coughing on someone, living in close quarters or dormitories (military recruits, students), sharing eating or drinking utensils, etc.) facilitate the spread of the disease. The average incubation period is 4 days, ranging between 2 and 10 days.

Twelve subtypes or serogroups of N. meningitidis have been identified and four (N. meningitidis. A, B, C and W135) are recognized to cause epidemics. The pathogenicity, immunogenicity, and epidemic capabilities differ according to the serogroup. Thus the identification of the serogroup responsible of a sporadic case is crucial for epidemic containment.

Determining how many people get viral meningitis is difficult because it often remains undiagnosed and is easily confused with the flu. The prognosis for viral meningitis is much better than that for bacterial meningitis, with most people recovering completely with simple treatment of the symptoms. Because antibiotics do not help viral infections, they are not useful in the treatment of viral meningitis.

The cause of most cases of meningitis is a viral infection, but bacterial and fungal infections also can lead to meningitis. The severity of the inflammation and the best treatment depend on the cause of the infection. Bacterial meningitis is generally much more serious than viral meningitis, and timely treatment is necessary.Bacterial meningitis is less common than viral meningitis but is usually much more serious and can be life-threatening if not treated promptly.

viral meningitis may occur as a complication in people with genital herpes. Recently, West Nile virus spread by mosquito bites has become a cause of viral meningitis in most of the U.S. In addition to causing viral meningitis, West Nile virus may cause encephalitis in some patients and a polio-like syndrome in others.

A new test that rapidly detects viral meningitis was approved by U.S. health officials.

The test, called the Xpert EV test, uses molecular biology and, when used with other tests, can help distinguish between viral meningitis and the less common, but more severe, bacterial meningitis, according to the U.S. Food and Drug Administration.

"Because this test is significantly faster than existing methods for diagnosing meningitis, it could minimize delays in treating patients," Dr. Daniel Schultz, director of the FDA's Center for Devices and Radiological Health, said in a prepared statement.

"Since bacterial meningitis can be deadly within as little as two days, patients who have viral meningitis are frequently treated with antibiotics as a safeguard against the more dangerous bacterial meningitis. This test should help physicians manage patients appropriately and prevent unnecessary treatment with antibiotics," Schultz added.

Meningitis is an infection of the spinal fluid that surrounds the spinal cord and brain. The illness is diagnosed by testing the fluid. Usually, getting results from tests for meningitis can take hours for some and up to a week for others. However, Xpert EV test results take only two and one-half hours, the FDA said.

Determining whether meningitis is viral or bacterial is crucial to early effective treatment. However, telling the two types apart is difficult because the symptoms are similar.

Patients with viral meningitis usually recover in about two weeks without any treatment. However, bacterial meningitis can cause brain damage, hearing loss and even death if not treated properly with antibiotics.

Symptoms for patients over 2 years of age include fever, severe headache, stiff neck, nausea, sleepiness, confusion, and sensitivity to bright lights or seizures. In newborns and infants, these symptoms may be hard to detect or not may occur. These young patients may only appear slow or inactive, or be irritable, have vomiting or feed poorly, according to the U.S. Centers for Disease Control and Prevention.

The Xpert EV test is the first fully automated test that isolates viral genetic material in a patient's cerebrospinal fluid using a process called "reverse transcription-polymerase chain reaction." The test identifies viruses responsible for about 90 percent of all viral meningitis cases, according to the FDA.

The test, developed by Cepheid of Sunnyvale, Calif., is done by adding the sample directly to a disposable cartridge. The cartridge is then placed into the GeneXpert DX instrument, which does all the laboratory procedures in a "one-step, easy-to-use format that helps minimize errors," the FDA said.

In a trial involving six medical institutions, the Xpert EV test was used to assess 255 patient samples. The result: 96 percent of patients who tested positive did have viral meningitis, while 97 percent of patients who tested negative did not have viral meningitis, the FDA said.

One expert said the test should cut the time to an accurate diagnosis.

"This test could be great," said Dr. Lise E. Nigrovic, an attending physician in pediatric emergency medicine at Children's Hospital Boston and an instructor in pediatrics at Harvard Medical School. "The issue is that clinicians can't tell the difference between viruses and bacteria."

"A test that could diagnose a virus while the patient is in the emergency room could help decision-making," Nigrovic added.

But another expert said he was concerned that using this test alone could cause some cases of bacterial meningitis to be missed.

"This could be a valuable test in addition to the tests we currently have available," said Dr. Nathan Litman, director of pediatrics and pediatric infectious diseases at Children's Hospital at Montefiore Medical Center, in New York City. "It could potentially avoid hospitalization and the administration of unnecessary antibiotics."

But, Litman added, the test is limited because it is not 100 percent sensitive or 100 percent specific. "We may end up treating some patients who have viral meningitis, which is not so bad," he said.

However, according to the trial results, 4 percent were diagnosed with viral meningitis and didn't have it, Litman noted. "If they had bacterial meningitis, and physicians were to rely solely on this test, they wouldn't treat these patients," he said. "That's why this test should be added to other tests that we routinely request when we examine for viral meningitis."

Dr. Steven Gutman, director of the FDA's Office of In Vitro Diagnostic Device Evaluation and Safety, agreed the test should not be used as a stand-alone for diagnosing viral meningitis. "The test is designed to be used along with other tests," he said.

Having to wait for other tests does mean that the quick turnaround of the Xpert EV test becomes a less important factor, he said.

People with less competent immune systems, such as the very young or those whose immune systems have been compromised by disease, are more at risk for all types of meningitis. Some types are more common in child-care centers, boarding schools, dormitories, and military bases, mainly because infectious diseases tend to spread quickly among large groups of people.

Travellers to areas affected by meningococcal outbreaks are advised to be vaccinated. For pilgrims to the Hajj and Ramadan Omra, Saudi Arabia requires visitors obtain a tetravalent vaccine (against A, C, Y, W135) at least ten days prior to their arrival in the country.


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