The government's first study of how well rapid tests diagnose swine flu finds they're wrong at least half the time.

The Centers for Disease Control and Prevention looked at rapid tests made by three companies. The tests correctly confirmed swine flu infections only 10 percent to 51 percent of the time. The tests were better at diagnosing seasonal flu.

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What should doctors do if a test comes back negative for a patient they think has the flu? The CDC says doctors should order a more precise lab test but in the meantime prescribe medicines like Tamiflu.

The results of the study were released Thursday.

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On the Net:

CDC: http://www.cdc.gov/H1N1FLU/