FDA approves preliminary test for norovirus

Feb 24, 2011 (CIDRAP News) – The US Food and Drug Administration (FDA) has announced approval of what it calls the first test for preliminary identification of norovirus, intended for use in outbreaks in which there is a likely transmission pathway.

The test, called the Ridascreen Norovirus 3rd Generation EIA assay, "is for use when a number of people have simultaneously contracted gastroenteritis and there is a clear avenue for virus transmission, such as a shared location or food," the FDA said in a news release yesterday. The test is made by R-Biopharm AG of Darmstadt, Germany.

"This test provides an avenue for early identification of norovirus. Early intervention can halt the spread of an outbreak," said Jeffrey Shuren, MD, JD, director of the FDA's Center for Devices and Radiological Health. The agency did not say how long the test takes to give a result.

The test is not sensitive enough for diagnosing norovirus infection in individual patients, the FDA said.

The manufacturer assessed the test's performance by comparing its results to the results of a norovirus reference standard test on 609 fecal samples. Ridascreen was found to be less sensitive than the standard test, as it detected norovirus in about two thirds of the samples in which it was present, the FDA said.

The FDA said it reviewed Ridascreen via the "de novo pathway," an alternative path to market for devices that are lower risk and may not require premarket approval but are of a new type and therefore might not clear the standard "510(K)" evaluation.

Foodborne disease expert Craig Hedberg, PhD, said new tests for norovirus may facilitate detection of the virus in more gastroenteritis outbreaks, but he expressed doubts about the potential impact of the new test. Hedberg is an associate professor of occupational and environmental health at the University of Minnesota School of Public Health in Minneapolis.

Citing the FDA statement that the test is for use when a number of illnesses have occurred and there is "a clear avenue for virus transmission," Hedberg said, "The clinical profile of these outbreaks is pretty clear already, and public health officials and others should respond rapidly to the occurrence of such outbreaks when 'there is a clear avenue for virus transmission' based on the clinical and epidemiological picture of the outbreak. The information that is an indication for testing using this product should directly lead to implementation of control measures.

"If officials delay action in order to test and confirm the presence of norovirus, we actually put more people at risk."

Hedberg added that Ridascreen is an enzyme-linked immunosorbent assay (EIA) that detects the virus but not the specific strain. Polymerase chain reaction (PCR), the standard test for norovirus, yields genetic sequence data that can be used for epidemiologic purposes, just as pulsed-field gel electrophoresis (PFGE) yields subtype information for Salmonella or Escherichia coli O157:H7, he said.

"If public health agencies use the EIA and do not follow that up with PCR confirmation, we will lose critical information about the emergence and distribution of different strains of norovirus," he added.

The Centers for Disease Control and Prevention (CDC), in online reference materials, says that commercial EIA tests for norovirus are not sensitive enough for diagnosing sporadic cases but may be useful for rapidly identifying the virus in outbreaks.

The FDA statement said the CDC will be updating its norovirus management and prevention guidelines in March, and the new version will probably reflect "substantial advances" in diagnostic methods and other areas.

See also:

Feb 23 FDA release

CDC information on norovirus diagnosis and testing

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