Thursday, April 30, 2009

Web resources on swine flu testing

Today, National Public Radio's Morning Edition commented on the prominent use of Internet resources in the unraveling swine flu pandemic. They mentioned the large number of followers of the CDC Twitt. The New York City Department of Health also has a Twitt, but it has not been updated since last Monday.

The U.S. Centers for Disease Control and Prevention (CDC) site is quoted most widely by on-line communities, such as the American Society of Microbiology's laboratory DivC discussion group.
In addition to Twitter, the CDC also offers a RSS feed. The CDC site includes a page discussing available rapid flu tests. The Federal Drug Administration (FDA) swine flu page offers e-mail updates and includes information on how to interpret the molecular (rRT-PCR) test for presumptive confirmation of the disease.

The World Health Organization swine flu site also offers a RSS feed. Medscape's swine flu alert center page has links to news, clinical reviews and articles.

Technical information about the CDC molecular test, such as specific target sequences, sample interference, performance with samples other than those collected in viral transport media, etc are not prominently available yet. In the meantime, the National Center for Biotechnology Information is gathering viral isolate sequences at breathtaking speed. Virologist Ruben Donis from the CDC, discussed molecular aspects of the swine flu strain in a ScienceInsider interview yesterday.

Wednesday, April 29, 2009

A negative rapid flu test result is worthless

The teacher of a first grade class in a school in a New York City suburb yesterday fell ill with chills, high temperature and muscle aches. The class is made up primarily by children of immigrant families, including ten from Mexico. Three of the children in the class had been out for a few days because of a disease characterized by a sore throat. The teacher was seen at a local Emergency Department (ED) and, after a rapid flu test, was told that she "did not have the swine flu".

What is wrong with this scenario?: (1) the null rule-out value of the rapid antigen test for the swine flu was not recognized, and (2) the patient epidemiological circumstances did not seem to have been addressed by the health care facility (even though they were aware of the risk to health care workers and held the patient in isolation while waiting for the test results).

The school nurses were well aware of the need to quickly rule out an outbreak, but had no idea whom to call for advice. I tried to help by calling the NY State's Swine Flu Hotline, but they referred me to a New York City physician resource, even though the school is outside the city limits. There was no information or contact links prominently listed on the CDC, State or County Health Department web sites for institutions to obtain rapid advice in situations where an outbreak is suspected.

Hopefully, this particular teacher's illness will end up being caused by something else, and the event will just be one of the numerous false alarms that will be triggered by the public concern about the disease. But the epidemic needs just one such institutional exposure incident to continue expanding in our midst. Institutions need instant clear guidance from local authorities in order to determine the need for timely and appropriate containment measures. Right now, this guidance is not easy to find.

Tuesday, April 28, 2009

Testing for Swine Flu

New York City (NYC) now has the largest number of confirmed cases in the U.S. The NYC Department of Health recommends testing only when people experience severe symptoms or fall sick in clusters. A negative rapid antigen, immunofluorescence or viral culture test does not rule out swine flu, according to the Centers for Disease Control and Prevention (CDC). Conversely, a suspected patient who tests positive for influenza A in a rapid antigen or immunofluorescent test, is considered a probable case of swine influenza A.

Confirmation requires a positive viral culture or a positive result of the molecular real-time polymerase chain reaction test (RT-PCR) for influenza A, B, H1 and H3 available in State Public Health Laboratories. This confirmatory test is indirect since even though the swine flu virus is type A(H1N1), the results are negative for H1. The direct confirmation test is currently only available at the CDC.

The nasal/pharyngeal swab used for the rapid flu antigen test might not be appropriate for the RT-PCR test. The later requires synthetic swab materials, viral transport media and transport at refrigerated or freezing (- 70 C) temperatures.

Monday, April 27, 2009

First

Clinical Laboratory Week just finished with a bang. The main tool to contain the potential pandemic of swine flu is a lab test. Yet this minute in the limelight will probably be wasted again. We will again be too busy in the lab to take advantage of the attention and explain to the general public the enormous importance of the clinical laboratory and the need for knowledge and skills among the lab staff, from the phlebotomist to the director, as well as the value of the industry supporting it.