BETHESDA, Md. - An FDA advisory panel delivered a confusing verdict on Friday about the use of Western blot tests for detecting HIV-1 antibodies in urine, a critical component of a urine-based AIDS test that Calypte Biomedical Corp. is seeking to market.

The Blood Products Advisory Committee voted 8-1, with 3 abstentions, that Calypte's test, when supported by detection of a single gp160 envelope protein band on the urine Western blot test, is sufficient to indicate a positive test result.

But the panel then voted 10-1, with 1 abstention, against recommending that the urine Western blot should be used as a stand-alone test without confirmation from a blood test.

The meeting ostensibly was about a supplement Cambridge Biotech Corp. (CBCXQ) has filed to extend use of its Western blot test to urine. The Cambridge Western blot is used to confirm half of the HIV positive blood tests in the U.S.

A coupled product

Most of the presentations, however, were made by Calypte, which also performed the clinical trials in support of the application. Calypte hopes to couple the CBCXQ test with its HIV-1 screening test.