Americans who have tested themselves at home for the AIDS virus may want to get an official test, the government warned yesterday after buying some HIV kits sold on the Internet--and discovering they gave false results.

"Using one of these kits could give a person who might be infected with HIV the false impression that he or she is not infected," the Federal Trade Commission warned in a consumer alert.

The FTC recently tested at-home HIV test kits sold over the Internet by using a known HIV-infected sample--so the tests should have signaled that the "user" was infected. Instead, in every case the kits signaled that the user was healthy.

Internet ads falsely state or imply that the kits were approved by the World Health Organization, the Food and Drug Administration or another well-known health organization.

In fact, the FDA has approved just one at-home test kit for the AIDS virus--Home Access Health Corp.'s Home Access Express HIV-1 Test System. The World Health Organization does not approve or license HIV tests, the consumer alert warned.

The FTC would neither confirm nor deny whether it was investigating sellers of the useless HIV tests that it tested, nor would it name the products.